path: root/netperf-2.4.4/doc/netperf.info

This is netperf.info, produced by makeinfo version 4.8 from
netperf.texi.

   This is Rick Jones' feeble attempt at a Texinfo-based manual for the
netperf benchmark.

   Copyright (C) 2005-2007 Hewlett-Packard Company

     Permission is granted to copy, distribute and/or modify this
     document per the terms of the netperf source licence, a copy of
     which can be found in the file `COPYING' of the basic netperf
     distribution.


File: netperf.info,  Node: Top,  Next: Introduction,  Prev: (dir),  Up: (dir)

Netperf Manual
**************

This is Rick Jones' feeble attempt at a Texinfo-based manual for the
netperf benchmark.

   Copyright (C) 2005-2007 Hewlett-Packard Company

     Permission is granted to copy, distribute and/or modify this
     document per the terms of the netperf source licence, a copy of
     which can be found in the file `COPYING' of the basic netperf
     distribution.

* Menu:

* Introduction::                An introduction to netperf - what it is and whatit is not.
* Installing Netperf::          How to go about installing netperf.
* The Design of Netperf::
* Global Command-line Options::
* Using Netperf to Measure Bulk Data Transfer::
* Using Netperf to Measure Request/Response ::
* Using Netperf to Measure Aggregate Performance::
* Using Netperf to Measure Bidirectional Transfer::
* Other Netperf Tests::
* Address Resolution::
* Enhancing Netperf::
* Netperf4::
* Concept Index::
* Option Index::

 --- The Detailed Node Listing ---

Introduction

* Conventions::

Installing Netperf

* Getting Netperf Bits::
* Installing Netperf Bits::
* Verifying Installation::

The Design of Netperf

* CPU Utilization::

Global Command-line Options

* Command-line Options Syntax::
* Global Options::

Using Netperf to Measure Bulk Data Transfer

* Issues in Bulk Transfer::
* Options common to TCP UDP and SCTP tests::

Options common to TCP UDP and SCTP tests

* TCP_STREAM::
* TCP_MAERTS::
* TCP_SENDFILE::
* UDP_STREAM::
* XTI_TCP_STREAM::
* XTI_UDP_STREAM::
* SCTP_STREAM::
* DLCO_STREAM::
* DLCL_STREAM::
* STREAM_STREAM::
* DG_STREAM::

Using Netperf to Measure Request/Response

* Issues in Request/Response::
* Options Common to TCP UDP and SCTP _RR tests::

Options Common to TCP UDP and SCTP _RR tests

* TCP_RR::
* TCP_CC::
* TCP_CRR::
* UDP_RR::
* XTI_TCP_RR::
* XTI_TCP_CC::
* XTI_TCP_CRR::
* XTI_UDP_RR::
* DLCL_RR::
* DLCO_RR::
* SCTP_RR::

Using Netperf to Measure Aggregate Performance

* Running Concurrent Netperf Tests::
* Using --enable-burst::

Using Netperf to Measure Bidirectional Transfer

* Bidirectional Transfer with Concurrent Tests::
* Bidirectional Transfer with TCP_RR::

Other Netperf Tests

* CPU rate calibration::


File: netperf.info,  Node: Introduction,  Next: Installing Netperf,  Prev: Top,  Up: Top

1 Introduction
**************

Netperf is a benchmark that can be use to measure various aspect of
networking performance.  The primary foci are bulk (aka unidirectional)
data transfer and request/response performance using either TCP or UDP
and the Berkeley Sockets interface.  As of this writing, the tests
available either unconditionally or conditionally include:

   * TCP and UDP unidirectional transfer and request/response over IPv4
     and IPv6 using the Sockets interface.

   * TCP and UDP unidirectional transfer and request/response over IPv4
     using the XTI interface.

   * Link-level unidirectional transfer and request/response using the
     DLPI interface.

   * Unix domain sockets

   * SCTP unidirectional transfer and request/response over IPv4 and
     IPv6 using the sockets interface.

   While not every revision of netperf will work on every platform
listed, the intention is that at least some version of netperf will
work on the following platforms:

   * Unix - at least all the major variants.

   * Linux

   * Windows

   * OpenVMS

   * Others

   Netperf is maintained and informally supported primarily by Rick
Jones, who can perhaps be best described as Netperf Contributing
Editor.  Non-trivial and very appreciated assistance comes from others
in the network performance community, who are too numerous to mention
here. While it is often used by them, netperf is NOT supported via any
of the formal Hewlett-Packard support channels.  You should feel free
to make enhancements and modifications to netperf to suit your
nefarious porpoises, so long as you stay within the guidelines of the
netperf copyright.  If you feel so inclined, you can send your changes
to netperf-feedback <netperf-feedback@netperf.org> for possible
inclusion into subsequent versions of netperf.

   If you would prefer to make contributions to networking benchmark
using certified "open source" license, please considuer netperf4, which
is distributed under the terms of the GPL.

   The netperf-talk <netperf-talk@netperf.org> mailing list is
available to discuss the care and feeding of netperf with others who
share your interest in network performance benchmarking. The
netperf-talk mailing list is a closed list and you must first subscribe
by sending email to netperf-talk-request
<netperf-talk-request@netperf.org>.

* Menu:

* Conventions::


File: netperf.info,  Node: Conventions,  Prev: Introduction,  Up: Introduction

1.1 Conventions
===============

A "sizespec" is a one or two item, comma-separated list used as an
argument to a command-line option that can set one or two, related
netperf parameters.  If you wish to set both parameters to separate
values, items should be separated by a comma:

     parameter1,parameter2

   If you wish to set the first parameter without altering the value of
the second from its default, you should follow the first item with a
comma:

     parameter1,

   Likewise, precede the item with a comma if you wish to set only the
second parameter:

     ,parameter2

   An item with no commas:

     parameter1and2

   will set both parameters to the same value.  This last mode is one of
the most frequently used.

   There is another variant of the comma-separated, two-item list called
a "optionspec" which is like a sizespec with the exception that a
single item with no comma:

     parameter1

   will only set the value of the first parameter and will leave the
second parameter at its default value.

   Netperf has two types of command-line options.  The first are global
command line options.  They are essentially any option not tied to a
particular test or group of tests.  An example of a global command-line
option is the one which sets the test type - `-t'.

   The second type of options are test-specific options.  These are
options which are only applicable to a particular test or set of tests.
An example of a test-specific option would be the send socket buffer
size for a TCP_STREAM test.

   Global command-line options are specified first with test-specific
options following after a `--' as in:

     netperf <global> -- <test-specific>


File: netperf.info,  Node: Installing Netperf,  Next: The Design of Netperf,  Prev: Introduction,  Up: Top

2 Installing Netperf
********************

Netperf's primary form of distribution is source code.  This allows
installation on systems other than those to which the authors have
ready access and thus the ability to create binaries.  There are two
styles of netperf installation.  The first runs the netperf server
program - netserver - as a child of inetd.  This requires the installer
to have sufficient privileges to edit the files `/etc/services' and
`/etc/inetd.conf' or their platform-specific equivalents.

   The second style is to run netserver as a standalone daemon.  This
second method does not require edit privileges on `/etc/services' and
`/etc/inetd.conf' but does mean you must remember to run the netserver
program explicitly after every system reboot.

   This manual assumes that those wishing to measure networking
performance already know how to use anonymous FTP and/or a web browser.
It is also expected that you have at least a passing familiarity with
the networking protocols and interfaces involved. In all honesty, if
you do not have such familiarity, likely as not you have some
experience to gain before attempting network performance measurements.
The excellent texts by authors such as Stevens, Fenner and Rudoff
and/or Stallings would be good starting points. There are likely other
excellent sources out there as well.

* Menu:

* Getting Netperf Bits::
* Installing Netperf Bits::
* Verifying Installation::


File: netperf.info,  Node: Getting Netperf Bits,  Next: Installing Netperf Bits,  Prev: Installing Netperf,  Up: Installing Netperf

2.1 Getting Netperf Bits
========================

Gzipped tar files of netperf sources can be retrieved via anonymous FTP
(ftp://ftp.netperf.org/netperf) for "released" versions of the bits.
Pre-release versions of the bits can be retrieved via anonymous FTP
from the experimental (ftp://ftp.netperf.org/netperf/experimental)
subdirectory.

   For convenience and ease of remembering, a link to the download site
is provided via the NetperfPage (http://www.netperf.org/)

   The bits corresponding to each discrete release of netperf are
tagged (http://www.netperf.org/svn/netperf2/tags) for retrieval via
subversion.  For example, there is a tag for the first version
corresponding to this version of the manual - netperf 2.4.3
(http://www.netperf.org/svn/netperf2/tags/netperf-2.4.3).  Those
wishing to be on the bleeding edge of netperf development can use
subversion to grab the top of trunk
(http://www.netperf.org/svn/netperf2/trunk).

   There are likely other places around the Internet from which one can
download netperf bits.  These may be simple mirrors of the main netperf
site, or they may be local variants on netperf.  As with anything one
downloads from the Internet, take care to make sure it is what you
really wanted and isn't some malicious Trojan or whatnot.  Caveat
downloader.

   As a general rule, binaries of netperf and netserver are not
distributed from ftp.netperf.org.  From time to time a kind soul or
souls has packaged netperf as a Debian package available via the
apt-get mechanism or as an RPM.  I would be most interested in learning
how to enhance the makefiles to make that easier for people, and
perhaps to generate HP-UX swinstall"depots."


File: netperf.info,  Node: Installing Netperf Bits,  Next: Verifying Installation,  Prev: Getting Netperf Bits,  Up: Installing Netperf

2.2 Installing Netperf
======================

Once you have downloaded the tar file of netperf sources onto your
system(s), it is necessary to unpack the tar file, cd to the netperf
directory, run configure and then make.  Most of the time it should be
sufficient to just:

     gzcat <netperf-version>.tar.gz | tar xf -
     cd <netperf-version>
     ./configure
     make
     make install

   Most of the "usual" configure script options should be present
dealing with where to install binaries and whatnot.
     ./configure --help
   should list all of those and more.

   If the netperf configure script does not know how to automagically
detect which CPU utilization mechanism to use on your platform you may
want to add a `--enable-cpuutil=mumble' option to the configure
command.   If you have knowledge and/or experience to contribute to
that area, feel free to contact <netperf-feedback@netperf.org>.

   Similarly, if you want tests using the XTI interface, Unix Domain
Sockets, DLPI or SCTP it will be necessary to add one or more
`--enable-[xti|unix|dlpi|sctp]=yes' options to the configure command.
As of this writing, the configure script will not include those tests
automagically.

   On some platforms, it may be necessary to precede the configure
command with a CFLAGS and/or LIBS variable as the netperf configure
script is not yet smart enough to set them itself.  Whenever possible,
these requirements will be found in `README.PLATFORM' files.  Expertise
and assistance in making that more automagical in the configure script
would be most welcome.

   Other optional configure-time settings include
`--enable-intervals=yes' to give netperf the ability to "pace" its
_STREAM tests and `--enable-histogram=yes' to have netperf keep a
histogram of interesting times.  Each of these will have some effect on
the measured result.  If your system supports `gethrtime()' the effect
of the histogram measurement should be minimized but probably still
measurable.  For example, the histogram of a netperf TCP_RR test will
be of the individual transaction times:
     netperf -t TCP_RR -H lag -v 2
     TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to lag.hpl.hp.com (15.4.89.214) port 0 AF_INET : histogram
     Local /Remote
     Socket Size   Request  Resp.   Elapsed  Trans.
     Send   Recv   Size     Size    Time     Rate
     bytes  Bytes  bytes    bytes   secs.    per sec

     16384  87380  1        1       10.00    3538.82
     32768  32768
     Alignment      Offset
     Local  Remote  Local  Remote
     Send   Recv    Send   Recv
         8      0       0      0
     Histogram of request/response times
     UNIT_USEC     :    0:    0:    0:    0:    0:    0:    0:    0:    0:    0
     TEN_USEC      :    0:    0:    0:    0:    0:    0:    0:    0:    0:    0
     HUNDRED_USEC  :    0: 34480:  111:   13:   12:    6:    9:    3:    4:    7
     UNIT_MSEC     :    0:   60:   50:   51:   44:   44:   72:  119:  100:  101
     TEN_MSEC      :    0:  105:    0:    0:    0:    0:    0:    0:    0:    0
     HUNDRED_MSEC  :    0:    0:    0:    0:    0:    0:    0:    0:    0:    0
     UNIT_SEC      :    0:    0:    0:    0:    0:    0:    0:    0:    0:    0
     TEN_SEC       :    0:    0:    0:    0:    0:    0:    0:    0:    0:    0
     >100_SECS: 0
     HIST_TOTAL:      35391

   Long-time users of netperf will notice the expansion of the main test
header.  This stems from the merging-in of IPv6 with the standard IPv4
tests and the addition of code to specify addressing information for
both sides of the data connection.

   The histogram you see above is basically a base-10 log histogram
where we can see that most of the transaction times were on the order
of one hundred to one-hundred, ninety-nine microseconds, but they were
occasionally as long as ten to nineteen milliseconds

   The `--enable-demo=yes' configure option will cause code to be
included to report interim results during a test run.  The rate at
which interim results are reported can then be controlled via the
global `-D' option.  Here is an example of -enable-demo mode output:

     src/netperf -D 1.35 -H lag -f M
     TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to lag.hpl.hp.com (15.4.89.214) port 0 AF_INET : demo
     Interim result:    9.66 MBytes/s over 1.67 seconds
     Interim result:    9.64 MBytes/s over 1.35 seconds
     Interim result:    9.58 MBytes/s over 1.36 seconds
     Interim result:    9.51 MBytes/s over 1.36 seconds
     Interim result:    9.71 MBytes/s over 1.35 seconds
     Interim result:    9.66 MBytes/s over 1.36 seconds
     Interim result:    9.61 MBytes/s over 1.36 seconds
     Recv   Send    Send
     Socket Socket  Message  Elapsed
     Size   Size    Size     Time     Throughput
     bytes  bytes   bytes    secs.    MBytes/sec

      32768  16384  16384    10.00       9.61

   Notice how the units of the interim result track that requested by
the `-f' option.  Also notice that sometimes the interval will be
longer than the value specified in the `-D' option.  This is normal and
stems from how demo mode is implemented without relying on interval
timers, but by calculating how many units of work must be performed to
take at least the desired interval.

   As of this writing, a `make install' will not actually update the
files `/etc/services' and/or `/etc/inetd.conf' or their
platform-specific equivalents.  It remains necessary to perform that
bit of installation magic by hand.  Patches to the makefile sources to
effect an automagic editing of the necessary files to have netperf
installed as a child of inetd would be most welcome.

   Starting the netserver as a standalone daemon should be as easy as:
     $ netserver
     Starting netserver at port 12865
     Starting netserver at hostname 0.0.0.0 port 12865 and family 0

   Over time the specifics of the messages netserver prints to the
screen may change but the gist will remain the same.

   If the compilation of netperf or netserver happens to fail, feel free
to contact <netperf-feedback@netperf.org> or join and ask in
<netperf-talk@netperf.org>.  However, it is quite important that you
include the actual compilation errors and perhaps even the configure
log in your email.  Otherwise, it will be that much more difficult for
someone to assist you.


File: netperf.info,  Node: Verifying Installation,  Prev: Installing Netperf Bits,  Up: Installing Netperf

2.3 Verifying Installation
==========================

Basically, once netperf is installed and netserver is configured as a
child of inetd, or launched as a standalone daemon, simply typing:
     netperf
   should result in output similar to the following:
     $ netperf
     TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to localhost.localdomain (127.0.0.1) port 0 AF_INET
     Recv   Send    Send
     Socket Socket  Message  Elapsed
     Size   Size    Size     Time     Throughput
     bytes  bytes   bytes    secs.    10^6bits/sec

      87380  16384  16384    10.00    2997.84


File: netperf.info,  Node: The Design of Netperf,  Next: Global Command-line Options,  Prev: Installing Netperf,  Up: Top

3 The Design of Netperf
***********************

Netperf is designed around a basic client-server model.  There are two
executables - netperf and netserver.  Generally you will only execute
the netperf program, with the netserver program being invoked by the
remote system's inetd or equivalent.  When you execute netperf, the
first that that will happen is the establishment of a control
connection to the remote system.  This connection will be used to pass
test configuration information and results to and from the remote
system.  Regardless of the type of test to be run, the control
connection will be a TCP connection using BSD sockets.  The control
connection can use either IPv4 or IPv6.

   Once the control connection is up and the configuration information
has been passed, a separate "data" connection will be opened for the
measurement itself using the API's and protocols appropriate for the
specified test.  When the test is completed, the data connection will
be torn-down and results from the netserver will be passed-back via the
control connection and combined with netperf's result for display to
the user.

   Netperf places no traffic on the control connection while a test is
in progress.  Certain TCP options, such as SO_KEEPALIVE, if set as your
systems' default, may put packets out on the control connection while a
test is in progress.  Generally speaking this will have no effect on
the results.

* Menu:

* CPU Utilization::


File: netperf.info,  Node: CPU Utilization,  Prev: The Design of Netperf,  Up: The Design of Netperf

3.1 CPU Utilization
===================

CPU utilization is an important, and alas all-too infrequently reported
component of networking performance.  Unfortunately, it can be one of
the most difficult metrics to measure accurately as many systems offer
mechanisms that are at best il-suited to measuring CPU utilization in
high interrupt rate (eg networking) situations.

   CPU utilization in netperf is reported as a value between 0 and 100%
regardless of the number of CPUs involved.  In addition to CPU
utilization, netperf will report a metric called a "service demand".
The service demand is the normalization of CPU utilization and work
performed.  For a _STREAM test it is the microseconds of CPU time
consumed to transfer on KB (K == 1024) of data.  For a _RR test it is
the microseconds of CPU time consumed processing a single transaction.
For both CPU utilization and service demand, lower is better.

   Service demand can be particularly useful when trying to gauge the
effect of a performance change.  It is essentially a measure of
efficiency, with smaller values being more efficient.

   Netperf is coded to be able to use one of several, generally
platform-specific CPU utilization measurement mechanisms.  Single
letter codes will be included in the CPU portion of the test banner to
indicate which mechanism was used on each of the local (netperf) and
remote (netserver) system.

   As of this writing those codes are:

`U'
     The CPU utilization measurement mechanism was unknown to netperf or
     netperf/netserver was not compiled to include CPU utilization
     measurements. The code for the null CPU utilization mechanism can
     be found in `src/netcpu_none.c'.

`I'
     An HP-UX-specific CPU utilization mechanism whereby the kernel
     incremented a per-CPU counter by one for each trip through the idle
     loop. This mechanism was only available on specially-compiled HP-UX
     kernels prior to HP-UX 10 and is mentioned here only for the sake
     of historical completeness and perhaps as a suggestion to those
     who might be altering other operating systems. While rather
     simple, perhaps even simplistic, this mechanism was quite robust
     and was not affected by the concerns of statistical methods, or
     methods attempting to track time in each of user, kernel,
     interrupt and idle modes which require quite careful accounting.
     It can be thought-of as the in-kernel version of the looper `L'
     mechanism without the context switch overhead. This mechanism
     required calibration.

`P'
     An HP-UX-specific CPU utilization mechanism whereby the kernel
     keeps-track of time (in the form of CPU cycles) spent in the kernel
     idle loop (HP-UX 10.0 to 11.23 inclusive), or where the kernel
     keeps track of time spent in idle, user, kernel and interrupt
     processing (HP-UX 11.23 and later).  The former requires
     calibration, the latter does not.  Values in either case are
     retrieved via one of the pstat(2) family of calls, hence the use
     of the letter `P'.  The code for these mechanisms is found in
     `src/netcpu_pstat.c' and `src/netcpu_pstatnew.c' respectively.

`K'
     A Solaris-specific CPU utilization mechanism where by the kernel
     keeps track of ticks (eg HZ) spent in the idle loop.  This method
     is statistical and is known to be inaccurate when the interrupt
     rate is above epsilon as time spent processing interrupts is not
     subtracted from idle.  The value is retrieved via a kstat() call -
     hence the use of the letter `K'.  Since this mechanism uses units
     of ticks (HZ) the calibration value should invariably match HZ.
     (Eg 100)  The code for this mechanism is implemented in
     `src/netcpu_kstat.c'.

`M'
     A Solaris-specific mechanism available on Solaris 10 and latter
     which uses the new microstate accounting mechanisms.  There are
     two, alas, overlapping, mechanisms.  The first tracks nanoseconds
     spent in user, kernel, and idle modes. The second mechanism tracks
     nanoseconds spent in interrupt.  Since the mechanisms overlap,
     netperf goes through some hand-waving to try to "fix" the problem.
     Since the accuracy of the handwaving cannot be completely
     determined, one must presume that while better than the `K'
     mechanism, this mechanism too is not without issues.  The values
     are retrieved via kstat() calls, but the letter code is set to `M'
     to distinguish this mechanism from the even less accurate `K'
     mechanism.  The code for this mechanism is implemented in
     `src/netcpu_kstat10.c'.

`L'
     A mechanism based on "looper"or "soaker" processes which sit in
     tight loops counting as fast as they possibly can. This mechanism
     starts a looper process for each known CPU on the system.  The
     effect of processor hyperthreading on the mechanism is not yet
     known.  This mechanism definitely requires calibration.  The code
     for the "looper"mechanism can be found in `src/netcpu_looper.c'

`N'
     A Microsoft Windows-specific mechanism, the code for which can be
     found in `src/netcpu_ntperf.c'.  This mechanism too is based on
     what appears to be a form of micro-state accounting and requires no
     calibration.  On laptops, or other systems which may dynamically
     alter the CPU frequency to minimize power consumtion, it has been
     suggested that this mechanism may become slightly confsed, in
     which case using BIOS settings to disable the power saving would
     be indicated.

`S'
     This mechanism uses `/proc/stat' on Linux to retrieve time (ticks)
     spent in idle mode.  It is thought but not known to be reasonably
     accurate.  The code for this mechanism can be found in
     `src/netcpu_procstat.c'.

`C'
     A mechanism somewhat similar to `S' but using the sysctl() call on
     BSD-like Operating systems (*BSD and MacOS X).  The code for this
     mechanism can be found in `src/netcpu_sysctl.c'.

`Others'
     Other mechanisms included in netperf in the past have included
     using the times() and getrusage() calls.  These calls are actually
     rather poorly suited to the task of measuring CPU overhead for
     networking as they tend to be process-specific and much
     network-related  processing can happen outside the context of a
     process, in places where it is not a given it will be charged to
     the correct, or even a process.  They are mentioned here as a
     warning to anyone seeing those mechanisms used in other networking
     benchmarks.  These mechanisms are not available in netperf 2.4.0
     and later.

   For many platforms, the configure script will chose the best
available CPU utilization mechanism.  However, some platforms have no
particularly good mechanisms.  On those platforms, it is probably best
to use the "LOOPER" mechanism which is basically some number of
processes (as many as there are processors) sitting in tight little
loops counting as fast as they can.  The rate at which the loopers
count when the system is believed to be idle is compared with the rate
when the system is running netperf and the ratio is used to compute CPU
utilization.

   In the past, netperf included some mechanisms that only reported CPU
time charged to the calling process.  Those mechanisms have been
removed from netperf versions 2.4.0 and later because they are
hopelessly inaccurate.  Networking can and often results in CPU time
being spent in places - such as interrupt contexts - that do not get
charged to a or the correct process.

   In fact, time spent in the processing of interrupts is a common issue
for many CPU utilization mechanisms.  In particular, the "PSTAT"
mechanism was eventually known to have problems accounting for certain
interrupt time prior to HP-UX 11.11 (11iv1).  HP-UX 11iv1 and later are
known to be good. The "KSTAT" mechanism is known to have problems on
all versions of Solaris up to and including Solaris 10.  Even the
microstate accounting available via kstat in Solaris 10 has issues,
though perhaps not as bad as those of prior versions.

   The /proc/stat mechanism under Linux is in what the author would
consider an "uncertain" category as it appears to be statistical, which
may also have issues with time spent processing interrupts.

   In summary, be sure to "sanity-check" the CPU utilization figures
with other mechanisms.  However, platform tools such as top, vmstat or
mpstat are often based on the same mechanisms used by netperf.


File: netperf.info,  Node: Global Command-line Options,  Next: Using Netperf to Measure Bulk Data Transfer,  Prev: The Design of Netperf,  Up: Top

4 Global Command-line Options
*****************************

This section describes each of the global command-line options
available in the netperf and netserver binaries.  Essentially, it is an
expanded version of the usage information displayed by netperf or
netserver when invoked with the `-h' global command-line option.

* Menu:

* Command-line Options Syntax::
* Global Options::


File: netperf.info,  Node: Command-line Options Syntax,  Next: Global Options,  Prev: Global Command-line Options,  Up: Global Command-line Options

4.1 Command-line Options Syntax
===============================

Revision 1.8 of netperf introduced enough new functionality to overrun
the English alphabet for mnemonic command-line option names, and the
author was not and is not quite ready to switch to the contemporary
`--mumble' style of command-line options. (Call him a Luddite).

   For this reason, the command-line options were split into two parts -
the first are the global command-line options.  They are options that
affect nearly any and every test type of netperf.  The second type are
the test-specific command-line options.  Both are entered on the same
command line, but they must be separated from one another by a `--' for
correct parsing.  Global command-line options come first, followed by
the `--' and then test-specific command-line options.  If there are no
test-specific options to be set, the `--' may be omitted.  If there are
no global command-line options to be set, test-specific options must
still be preceded by a `--'.  For example:
     netperf <global> -- <test-specific>
   sets both global and test-specific options:
     netperf <global>
   sets just global options and:
     netperf -- <test-specific>
   sets just test-specific options.


File: netperf.info,  Node: Global Options,  Prev: Command-line Options Syntax,  Up: Global Command-line Options

4.2 Global Options
==================

`-a <sizespec>'
     This option allows you to alter the alignment of the buffers used
     in the sending and receiving calls on the local system.. Changing
     the alignment of the buffers can force the system to use different
     copy schemes, which can have a measurable effect on performance.
     If the page size for the system were 4096 bytes, and you want to
     pass page-aligned buffers beginning on page boundaries, you could
     use `-a 4096'.  By default the units are bytes, but suffix of "G,"
     "M," or "K" will specify the units to be 2^30 (GB), 2^20 (MB) or
     2^10 (KB) respectively. A suffix of "g," "m" or "k" will specify
     units of 10^9, 10^6 or 10^3 bytes respectively. [Default: 8 bytes]

`-A <sizespec>'
     This option is identical to the `-a' option with the difference
     being it affects alignments for the remote system.

`-b <size>'
     This option is only present when netperf has been configure with
     -enable-intervals=yes prior to compilation.  It sets the size of
     the burst of send calls in a _STREAM test.  When used in
     conjunction with the `-w' option it can cause the rate at which
     data is sent to be "paced."

`-B <string>'
     This option will cause `<string>' to be appended to the brief (see
     -P) output of netperf.

`-c [rate]'
     This option will ask that CPU utilization and service demand be
     calculated for the local system.  For those CPU utilization
     mechanisms requiring calibration, the options rate parameter may
     be specified to preclude running another calibration step, saving
     40 seconds of time.  For those CPU utilization mechanisms
     requiring no calibration, the optional rate parameter will be
     utterly and completely ignored.  [Default: no CPU measurements]

`-C [rate]'
     This option requests CPU utilization and service demand
     calculations for the remote system.  It is otherwise identical to
     the `-c' option.

`-d'
     Each instance of this option will increase the quantity of
     debugging output displayed during a test.  If the debugging output
     level is set high enough, it may have a measurable effect on
     performance.  Debugging information for the local system is
     printed to stdout.  Debugging information for the remote system is
     sent by default to the file `/tmp/netperf.debug'. [Default: no
     debugging output]

`-D [interval,units]'
     This option is only available when netperf is configured with
     -enable-demo=yes.  When set, it will cause netperf to emit periodic
     reports of performance during the run.  [INTERVAL,UNITS] follow
     the semantics of an optionspec. If specified, INTERVAL gives the
     minimum interval in real seconds, it does not have to be whole
     seconds.  The UNITS value can be used for the first guess as to
     how many units of work (bytes or transactions) must be done to
     take at least INTERVAL seconds. If omitted, INTERVAL defaults to
     one second and UNITS to values specific to each test type.

`-f G|M|K|g|m|k'
     This option can be used to change the reporting units for _STREAM
     tests.  Arguments of "G," "M," or "K" will set the units to 2^30,
     2^20 or 2^10 bytes/s respectively (EG power of two GB, MB or KB).
     Arguments of "g," ",m" or "k" will set the units to 10^9, 10^6 or
     10^3 bits/s respectively.  [Default: 'm' or 10^6 bits/s]

`-F <fillfile>'
     This option specified the file from which send which buffers will
     be pre-filled .  While the buffers will contain data from the
     specified file, the file is not fully transfered to the remote
     system as the receiving end of the test will not write the
     contents of what it receives to a file.  This can be used to
     pre-fill the send buffers with data having different
     compressibility and so is useful when measuring performance over
     mechanisms which perform compression.

     While optional for most tests, this option is required for a test
     utilizing the sendfile() or related calls because sendfile tests
     need a name of a file to reference.

`-h'
     This option causes netperf to display its usage string and exit to
     the exclusion of all else.

`-H <optionspec>'
     This option will set the name of the remote system and or the
     address family used for the control connection.  For example:
          -H linger,4
     will set the name of the remote system to "tardy" and tells
     netperf to use IPv4 addressing only.
          -H ,6
     will leave the name of the remote system at its default, and
     request that only IPv6 addresses be used for the control
     connection.
          -H lag
     will set the name of the remote system to "lag" and leave the
     address family to AF_UNSPEC which means selection of IPv4 vs IPv6
     is left to the system's address resolution.

     A value of "inet" can be used in place of "4" to request IPv4 only
     addressing.  Similarly, a value of "inet6" can be used in place of
     "6" to request IPv6 only addressing.  A value of "0" can be used
     to request either IPv4 or IPv6 addressing as name resolution
     dictates.

     By default, the options set with the global `-H' option are
     inherited by the test for its data connection, unless a
     test-specific `-H' option is specified.

     If a `-H' option follows either the `-4' or `-6' options, the
     family setting specified with the -H option will override the `-4'
     or `-6' options for the remote address family. If no address
     family is specified, settings from a previous `-4' or `-6' option
     will remain.  In a nutshell, the last explicit global command-line
     option wins.

     [Default:  "localhost" for the remote name/IP address and "0" (eg
     AF_UNSPEC) for the remote address family.]

`-I <optionspec>'
     This option enables the calculation of confidence intervals and
     sets the confidence and width parameters with the first have of the
     optionspec being either 99 or 95 for 99% or 95% confidence
     respectively.  The second value of the optionspec specifies the
     width of the desired confidence interval.  For example
          -I 99,5
     asks netperf to be 99% confident that the measured mean values for
     throughput and CPU utilization are within +/- 2.5% of the "real"
     mean values.  If the `-i' option is specified and the `-I' option
     is omitted, the confidence defaults to 99% and the width to 5%
     (giving +/- 2.5%)

     If netperf calculates that the desired confidence intervals have
     not been met, it emits a noticeable warning that cannot be
     suppressed with the `-P' or `-v' options:

          netperf -H tardy.cup -i 3 -I 99,5
          TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to tardy.cup.hp.com (15.244.44.58) port 0 AF_INET : +/-2.5%  99% conf.
          !!! WARNING
          !!! Desired confidence was not achieved within the specified iterations.
          !!! This implies that there was variability in the test environment that
          !!! must be investigated before going further.
          !!! Confidence intervals: Throughput      :  6.8%
          !!!                       Local CPU util  :  0.0%
          !!!                       Remote CPU util :  0.0%

          Recv   Send    Send
          Socket Socket  Message  Elapsed
          Size   Size    Size     Time     Throughput
          bytes  bytes   bytes    secs.    10^6bits/sec

           32768  16384  16384    10.01      40.23

     Where we see that netperf did not meet the desired convidence
     intervals.  Instead of being 99% confident it was within +/- 2.5%
     of the real mean value of throughput it is only confident it was
     within +/-3.4%.  In this example, increasing the `-i' option
     (described below) and/or increasing the iteration length with the
     `-l' option might resolve the situation.

`-i <sizespec>'
     This option enables the calculation of confidence intervals and
     sets the minimum and maximum number of iterations to run in
     attempting to achieve the desired confidence interval.  The first
     value sets the maximum number of iterations to run, the second,
     the minimum.  The maximum number of iterations is silently capped
     at 30 and the minimum is silently floored at 3.  Netperf repeats
     the measurement the minimum number of iterations and continues
     until it reaches either the desired confidence interval, or the
     maximum number of iterations, whichever comes first.

     If the `-I' option is specified and the `-i' option omitted the
     maximum number of iterations is set to 10 and the minimum to three.

     If netperf determines that the desired confidence intervals have
     not been met, it emits a noticeable warning.

     The total test time will be somewhere between the minimum and
     maximum number of iterations multiplied by the test length
     supplied by the `-l' option.

`-l testlen'
     This option controls the length of any one iteration of the
     requested test.  A positive value for TESTLEN will run each
     iteration of the test for at least TESTLEN seconds.  A negative
     value for TESTLEN will run each iteration for the absolute value of
     TESTLEN transactions for a _RR test or bytes for a _STREAM test.
     Certain tests, notably those using UDP can only be timed, they
     cannot be limited by transaction or byte count.

     In some situations, individual iterations of a test may run for
     longer for the number of seconds specified by the `-l' option.  In
     particular, this may occur for those tests where the socket buffer
     size(s) are significantly longer than the bandwidthXdelay product
     of the link(s) over which the data connection passes, or those
     tests where there may be non-trivial numbers of retransmissions.

     If confidence intervals are enabled via either `-I' or `-i' the
     total length of the netperf test will be somewhere between the
     minimum and maximum iteration count multiplied by TESTLEN.

`-L <optionspec>'
     This option is identical to the `-H' option with the difference
     being it sets the _local_ hostname/IP and/or address family
     information.  This option is generally unnecessary, but can be
     useful when you wish to make sure that the netperf control and data
     connections go via different paths.  It can also come-in handy if
     one is trying to run netperf through those evil, end-to-end
     breaking things known as firewalls.

     [Default: 0.0.0.0 (eg INADDR_ANY) for IPv4 and ::0 for IPv6 for the
     local name.  AF_UNSPEC for the local address family.]

`-n numcpus'
     This option tells netperf how many CPUs it should ass-u-me are
     active on the system running netperf.  In particular, this is used
     for the *Note CPU utilization: CPU Utilization. and service demand
     calculations.  On certain systems, netperf is able to determine
     the number of CPU's automagically. This option will override any
     number netperf might be able to determine on its own.

     Note that this option does _not_ set the number of CPUs on the
     system running netserver.  When netperf/netserver cannot
     automagically determine the number of CPUs that can only be set
     for netserver via a netserver `-n' command-line option.

`-N'
     This option tells netperf to forego establishing a control
     connection. This makes it is possible to run some limited netperf
     tests without a corresponding netserver on the remote system.

     With this option set, the test to be run is to get all the
     addressing information it needs to establish its data connection
     from the command line or internal defaults.  If not otherwise
     specified by test-specific command line options, the data
     connection for a "STREAM" or "SENDFILE" test will be to the
     "discard" port, an "RR" test will be to the "echo" port, and a
     "MEARTS" test will be to the chargen port.

     The response size of an "RR" test will be silently set to be the
     same as the request size.  Otherwise the test would hang if the
     response size was larger than the request size, or would report an
     incorrect, inflated transaction rate if the response size was less
     than the request size.

     Since there is no control connection when this option is
     specified, it is not possible to set "remote" properties such as
     socket buffer size and the like via the netperf command line. Nor
     is it possible to retrieve such interesting remote information as
     CPU utilization.  These items will be set to values which when
     displayed should make it immediately obvious that was the case.

     The only way to change remote characteristics such as socket buffer
     size or to obtain information such as CPU utilization is to employ
     platform-specific methods on the remote system.  Frankly, if one
     has access to the remote system to employ those methods one aught
     to be able to run a netserver there.  However, that ability may
     not be present in certain "support" situations, hence the addition
     of this option.

     Added in netperf 2.4.3.

`-o <sizespec>'
     The value(s) passed-in with this option will be used as an offset
     added to the alignment specified with the `-a' option.  For
     example:
          -o 3 -a 4096
     will cause the buffers passed to the local send and receive calls
     to begin three bytes past an address aligned to 4096 bytes.
     [Default: 0 bytes]

`-O <sizespec>'
     This option behaves just as the `-o' option but on the remote
     system and in conjunction with the `-A' option. [Default: 0 bytes]

`-p <optionspec>'
     The first value of the optionspec passed-in with this option tells
     netperf the port number at which it should expect the remote
     netserver to be listening for control connections.  The second
     value of the optionspec will request netperf to bind to that local
     port number before establishing the control connection.  For
     example
          -p 12345
     tells netperf that the remote netserver is listening on port 12345
     and leaves selection of the local port number for the control
     connection up to the local TCP/IP stack whereas
          -p ,32109
     leaves the remote netserver port at the default value of 12865 and
     causes netperf to bind to the local port number 32109 before
     connecting to the remote netserver.

     In general, setting the local port number is only necessary when
     one is looking to run netperf through those evil, end-to-end
     breaking things known as firewalls.

`-P 0|1'
     A value of "1" for the `-P' option will enable display of the test
     banner.  A value of "0" will disable display of the test banner.
     One might want to disable display of the test banner when running
     the same basic test type (eg TCP_STREAM) multiple times in
     succession where the test banners would then simply be redundant
     and unnecessarily clutter the output. [Default: 1 - display test
     banners]

`-t testname'
     This option is used to tell netperf which test you wish to run.
     As of this writing, valid values for TESTNAME include:
        * *Note TCP_STREAM::, *Note TCP_MAERTS::, *Note TCP_SENDFILE::,
          *Note TCP_RR::, *Note TCP_CRR::, *Note TCP_CC::

        * *Note UDP_STREAM::, *Note UDP_RR::

        * *Note XTI_TCP_STREAM::,  *Note XTI_TCP_RR::, *Note
          XTI_TCP_CRR::, *Note XTI_TCP_CC::

        * *Note XTI_UDP_STREAM::, *Note XTI_UDP_RR::

        * *Note SCTP_STREAM::, *Note SCTP_RR::

        * *Note DLCO_STREAM::, *Note DLCO_RR::,  *Note DLCL_STREAM::,
          *Note DLCL_RR::

        * *Note LOC_CPU: Other Netperf Tests, *Note REM_CPU: Other
          Netperf Tests.
     Not all tests are always compiled into netperf.  In particular, the
     "XTI," "SCTP," "UNIX," and "DL*" tests are only included in
     netperf when configured with `--enable-[xti|sctp|unix|dlpi]=yes'.

     Netperf only runs one type of test no matter how many `-t' options
     may be present on the command-line.  The last `-t' global
     command-line option will determine the test to be run. [Default:
     TCP_STREAM]

`-v verbosity'
     This option controls how verbose netperf will be in its output,
     and is often used in conjunction with the `-P' option. If the
     verbosity is set to a value of "0" then only the test's SFM (Single
     Figure of Merit) is displayed.  If local *Note CPU utilization:
     CPU Utilization. is requested via the `-c' option then the SFM is
     the local service demand.  Othersise, if remote CPU utilization is
     requested via the `-C' option then the SFM is the remote service
     demand.  If neither local nor remote CPU utilization are requested
     the SFM will be the measured throughput or transaction rate as
     implied by the test specified with the `-t' option.

     If the verbosity level is set to "1" then the "normal" netperf
     result output for each test is displayed.

     If the verbosity level is set to "2" then "extra" information will
     be displayed.  This may include, but is not limited to the number
     of send or recv calls made and the average number of bytes per
     send or recv call, or a histogram of the time spent in each send()
     call or for each transaction if netperf was configured with
     `--enable-histogram=yes'. [Default: 1 - normal verbosity]

`-w time'
     If netperf was configured with `--enable-intervals=yes' then this
     value will set the inter-burst time to time milliseconds, and the
     `-b' option will set the number of sends per burst.  The actual
     inter-burst time may vary depending on the system's timer
     resolution.

`-W <sizespec>'
     This option controls the number of buffers in the send (first or
     only value) and or receive (second or only value) buffer rings.
     Unlike some benchmarks, netperf does not continuously send or
     receive from a single buffer.  Instead it rotates through a ring of
     buffers. [Default: One more than the size of the send or receive
     socket buffer sizes (`-s' and/or `-S' options) divided by the send
     `-m' or receive `-M' buffer size respectively]

`-4'
     Specifying this option will set both the local and remote address
     families to AF_INET - that is use only IPv4 addresses on the
     control connection.  This can be overridden by a subsequent `-6',
     `-H' or `-L' option.  Basically, the last option explicitly
     specifying an address family wins.  Unless overridden by a
     test-specific option, this will be inherited for the data
     connection as well.

`-6'
     Specifying this option will set both local and and remote address
     families to AF_INET6 - that is use only IPv6 addresses on the
     control connection.  This can be overridden by a subsequent `-4',
     `-H' or `-L' option.  Basically, the last address family
     explicitly specified wins.  Unless overridden by a test-specific
     option, this will be inherited for the data connection as well.



File: netperf.info,  Node: Using Netperf to Measure Bulk Data Transfer,  Next: Using Netperf to Measure Request/Response,  Prev: Global Command-line Options,  Up: Top

5 Using Netperf to Measure Bulk Data Transfer
*********************************************

The most commonly measured aspect of networked system performance is
that of bulk or unidirectional transfer performance.  Everyone wants to
know how many bits or bytes per second they can push across the
network. The netperf convention for a bulk data transfer test name is
to tack a "_STREAM" suffix to a test name.

* Menu:

* Issues in Bulk Transfer::
* Options common to TCP UDP and SCTP tests::


File: netperf.info,  Node: Issues in Bulk Transfer,  Next: Options common to TCP UDP and SCTP tests,  Prev: Using Netperf to Measure Bulk Data Transfer,  Up: Using Netperf to Measure Bulk Data Transfer

5.1 Issues in Bulk Transfer
===========================

There are any number of things which can affect the performance of a
bulk transfer test.

   Certainly, absent compression, bulk-transfer tests can be limited by
the speed of the slowest link in the path from the source to the
destination.  If testing over a gigabit link, you will not see more
than a gigabit :) Such situations can be described as being
"network-limited" or "NIC-limited".

   CPU utilization can also affect the results of a bulk-transfer test.
If the networking stack requires a certain number of instructions or
CPU cycles per KB of data transferred, and the CPU is limited in the
number of instructions or cycles it can provide, then the transfer can
be described as being "CPU-bound".

   A bulk-transfer test can be CPU bound even when netperf reports less
than 100% CPU utilization.  This can happen on an MP system where one
or more of the CPUs saturate at 100% but other CPU's remain idle.
Typically, a single flow of data, such as that from a single instance
of a netperf _STREAM test cannot make use of much more than the power
of one CPU. Exceptions to this generally occur when netperf and/or
netserver run on CPU(s) other than the CPU(s) taking interrupts from
the NIC(s).

   Distance and the speed-of-light can affect performance for a
bulk-transfer; often this can be mitigated by using larger windows.
One common limit to the performance of a transport using window-based
flow-control is:
     Throughput <= WindowSize/RoundTripTime
   As the sender can only have a window's-worth of data outstanding on
the network at any one time, and the soonest the sender can receive a
window update from the receiver is one RoundTripTime (RTT).  TCP and
SCTP are examples of such protocols.

   Packet losses and their effects can be particularly bad for
performance.  This is especially true if the packet losses result in
retransmission timeouts for the protocol(s) involved.  By the time a
retransmission timeout has happened, the flow or connection has sat
idle for a considerable length of time.

   On many platforms, some variant on the `netstat' command can be used
to retrieve statistics about packet loss and retransmission. For
example:
     netstat -p tcp
   will retrieve TCP statistics on the HP-UX Operating System.  On other
platforms, it may not be possible to retrieve statistics for a specific
protocol and something like:
     netstat -s
   would be used instead.

   Many times, such network statistics are keep since the time the stack
started, and we are only really interested in statistics from when
netperf was running.  In such situations something along the lines of:
     netstat -p tcp > before
     netperf -t TCP_mumble...
     netstat -p tcp > after
   is indicated.  The beforeafter
(ftp://ftp.cup.hp.com/dist/networking/tools/) utility can be used to
subtract the statistics in `before' from the statistics in `after'
     beforeafter before after > delta
   and then one can look at the statistics in `delta'.  Beforeafter is
distributed in source form so one can compile it on the platofrm(s) of
interest.

   While it was written with HP-UX's netstat in mind, the annotated
netstat
(ftp://ftp.cup.hp.com/dist/networking/briefs/annotated_netstat.txt)
writeup may be helpful with other platforms as well.


File: netperf.info,  Node: Options common to TCP UDP and SCTP tests,  Prev: Issues in Bulk Transfer,  Up: Using Netperf to Measure Bulk Data Transfer

5.2 Options common to TCP UDP and SCTP tests
============================================

Many "test-specific" options are actually common across the different
tests.  For those tests involving TCP, UDP and SCTP, whether using the
BSD Sockets or the XTI interface those common options include:

`-h'
     Display the test-suite-specific usage string and exit.  For a TCP_
     or UDP_ test this will be the usage string from the source file
     nettest_bsd.c.  For an XTI_ test, this will be the usage string
     from the source file nettest_xti.c.  For an SCTP test, this will
     be the usage string from the source file nettest_sctp.c.

`-H <optionspec>'
     Normally, the remote hostname|IP and address family information is
     inherited from the settings for the control connection (eg global
     command-line `-H', `-4' and/or `-6' options).  The test-specific
     `-H' will override those settings for the data (aka test)
     connection only.  Settings for the control connection are left
     unchanged.

`-L <optionspec>'
     The test-specific `-L' option is identical to the test-specific
     `-H' option except it affects the local hostname|IP and address
     family information.  As with its global command-line counterpart,
     this is generally only useful when measuring though those evil,
     end-to-end breaking things called firewalls.

`-m bytes'
     Set the size of the buffer passed-in to the "send" calls of a
     _STREAM test.  Note that this may have only an indirect effect on
     the size of the packets sent over the network, and certain Layer 4
     protocols do _not_ preserve or enforce message boundaries, so
     setting `-m' for the send size does not necessarily mean the
     receiver will receive that many bytes at any one time. By default
     the units are bytes, but suffix of "G," "M," or "K" will specify
     the units to be 2^30 (GB), 2^20 (MB) or 2^10 (KB) respectively. A
     suffix of "g," "m" or "k" will specify units of 10^9, 10^6 or 10^3
     bytes respectively. For example:
          `-m 32K'
     will set the size to 32KB or 32768 bytes. [Default: the local send
     socket buffer size for the connection - either the system's
     default or the value set via the `-s' option.]

`-M bytes'
     Set the size of the buffer passed-in to the "recv" calls of a
     _STREAM test.  This will be an upper bound on the number of bytes
     received per receive call. By default the units are bytes, but
     suffix of "G," "M," or "K" will specify the units to be 2^30 (GB),
     2^20 (MB) or 2^10 (KB) respectively.  A suffix of "g," "m" or "k"
     will specify units of 10^9, 10^6 or 10^3 bytes respectively. For
     example:
          `-M 32K'
     will set the size to 32KB or 32768 bytes. [Default: the remote
     receive socket buffer size for the data connection - either the
     system's default or the value set via the `-S' option.]

`-P <optionspec>'
     Set the local and/or remote port numbers for the data connection.

`-s <sizespec>'
     This option sets the local send and receive socket buffer sizes for
     the data connection to the value(s) specified.  Often, this will
     affect the advertised and/or effective TCP or other window, but on
     some platforms it may not. By default the units are bytes, but
     suffix of "G," "M," or "K" will specify the units to be 2^30 (GB),
     2^20 (MB) or 2^10 (KB) respectively.  A suffix of "g," "m" or "k"
     will specify units of 10^9, 10^6 or 10^3 bytes respectively. For
     example:
          `-s 128K'
     Will request the local send and receive socket buffer sizes to be
     128KB or 131072 bytes.

     While the historic expectation is that setting the socket buffer
     size has a direct effect on say the TCP window, today that may not
     hold true for all stacks. Further, while the historic expectation
     is that the value specified in a setsockopt() call will be the
     value returned via a getsockopt() call, at least one stack is
     known to deliberately ignore history.  When running under Windows
     a value of 0 may be used which will be an indication to the stack
     the user wants to enable a form of copy avoidance. [Default: -1 -
     use the system's default socket buffer sizes]

`-S <sizespec>'
     This option sets the remote send and/or receive socket buffer sizes
     for the data connection to the value(s) specified.  Often, this
     will affect the advertised and/or effective TCP or other window,
     but on some platforms it may not. By default the units are bytes,
     but suffix of "G," "M," or "K" will specify the units to be 2^30
     (GB), 2^20 (MB) or 2^10 (KB) respectively.  A suffix of "g," "m"
     or "k" will specify units of 10^9, 10^6 or 10^3 bytes respectively.
     For example:
          `-s 128K'
     Will request the local send and receive socket buffer sizes to be
     128KB or 131072 bytes.

     While the historic expectation is that setting the socket buffer
     size has a direct effect on say the TCP window, today that may not
     hold true for all stacks.  Further, while the historic expectation
     is that the value specified in a setsockopt() call will be the
     value returned via a getsockopt() call, at least one stack is
     known to deliberately ignore history.  When running under Windows
     a value of 0 may be used which will be an indication to the stack
     the user wants to enable a form of copy avoidance. [Default: -1 -
     use the system's default socket buffer sizes]

`-4'
     Set the local and remote address family for the data connection to
     AF_INET - ie use IPv4 addressing only.  Just as with their global
     command-line counterparts the last of the `-4', `-6', `-H' or `-L'
     option wins for their respective address families.

`-6'
     This option is identical to its `-4' cousin, but requests IPv6
     addresses for the local and remote ends of the data connection.


* Menu:

* TCP_STREAM::
* TCP_MAERTS::
* TCP_SENDFILE::
* UDP_STREAM::
* XTI_TCP_STREAM::
* XTI_UDP_STREAM::
* SCTP_STREAM::
* DLCO_STREAM::
* DLCL_STREAM::
* STREAM_STREAM::
* DG_STREAM::


File: netperf.info,  Node: TCP_STREAM,  Next: TCP_MAERTS,  Prev: Options common to TCP UDP and SCTP tests,  Up: Options common to TCP UDP and SCTP tests

5.2.1 TCP_STREAM
----------------

The TCP_STREAM test is the default test in netperf.  It is quite
simple, transferring some quantity of data from the system running
netperf to the system running netserver.  While time spent establishing
the connection is not included in the throughput calculation, time
spent flushing the last of the data to the remote at the end of the
test is.  This is how netperf knows that all the data it sent was
received by the remote.  In addition to the *Note options common to
STREAM tests: Options common to TCP UDP and SCTP tests, the following
test-specific options can be included to possibly alter the behavior of
the test:

`-C'
     This option will set TCP_CORK mode on the data connection on those
     systems where TCP_CORK is defined (typically Linux).  A full
     description of TCP_CORK is beyond the scope of this manual, but in
     a nutshell it forces sub-MSS sends to be buffered so every segment
     sent is Maximum Segment Size (MSS) unless the application performs
     an explicit flush operation or the connection is closed.  At
     present netperf does not perform any explicit flush operations.
     Setting TCP_CORK may improve the bitrate of tests where the "send
     size" (`-m' option) is smaller than the MSS.  It should also
     improve (make smaller) the service demand.

     The Linux tcp(7) manpage states that TCP_CORK cannot be used in
     conjunction with TCP_NODELAY (set via the `-d' option), however
     netperf does not validate command-line options to enforce that.

`-D'
     This option will set TCP_NODELAY on the data connection on those
     systems where TCP_NODELAY is defined.  This disables something
     known as the Nagle Algorithm, which is intended to make the
     segments TCP sends as large as reasonably possible.  Setting
     TCP_NODELAY for a TCP_STREAM test should either have no effect
     when the send size (`-m' option) is larger than the MSS or will
     decrease reported bitrate and increase service demand when the
     send size is smaller than the MSS.  This stems from TCP_NODELAY
     causing each sub-MSS send to be its own TCP segment rather than
     being aggregated with other small sends.  This means more trips up
     and down the protocol stack per KB of data transferred, which
     means greater CPU utilization.

     If setting TCP_NODELAY with `-D' affects throughput and/or service
     demand for tests where the send size (`-m') is larger than the MSS
     it suggests the TCP/IP stack's implementation of the Nagle
     Algorithm _may_ be broken, perhaps interpreting the Nagle
     Algorithm on a segment by segment basis rather than the proper user
     send by user send basis.  However, a better test of this can be
     achieved with the *Note TCP_RR:: test.


   Here is an example of a basic TCP_STREAM test, in this case from a
Debian Linux (2.6 kernel) system to an HP-UX 11iv2 (HP-UX 11.23) system:

     $ netperf -H lag
     TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to lag.hpl.hp.com (15.4.89.214) port 0 AF_INET
     Recv   Send    Send
     Socket Socket  Message  Elapsed
     Size   Size    Size     Time     Throughput
     bytes  bytes   bytes    secs.    10^6bits/sec

      32768  16384  16384    10.00      80.42

   We see that the default receive socket buffer size for the receiver
(lag - HP-UX 11.23) is 32768 bytes, and the default socket send buffer
size for the sender (Debian 2.6 kernel) is 16384 bytes.  Througput is
expressed as 10^6 (aka Mega) bits per second, and the test ran for 10
seconds.  IPv4 addresses (AF_INET) were used.


File: netperf.info,  Node: TCP_MAERTS,  Next: TCP_SENDFILE,  Prev: TCP_STREAM,  Up: Options common to TCP UDP and SCTP tests

5.2.2 TCP_MAERTS
----------------

A TCP_MAERTS (MAERTS is STREAM backwards) test is "just like" a *Note
TCP_STREAM:: test except the data flows from the netserver to the
netperf. The global command-line `-F' option is ignored for this test
type.  The test-specific command-line `-C' option is ignored for this
test type.

   Here is an example of a TCP_MAERTS test between the same two systems
as in the example for the *Note TCP_STREAM:: test.  This time we request
larger socket buffers with `-s' and `-S' options:

     $ netperf -H lag -t TCP_MAERTS -- -s 128K -S 128K
     TCP MAERTS TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to lag.hpl.hp.com (15.4.89.214) port 0 AF_INET
     Recv   Send    Send
     Socket Socket  Message  Elapsed
     Size   Size    Size     Time     Throughput
     bytes  bytes   bytes    secs.    10^6bits/sec

     221184 131072 131072    10.03      81.14

   Where we see that Linux, unlike HP-UX, may not return the same value
in a getsockopt() as was requested in the prior setsockopt().

   This test is included more for benchmarking convenience than anything
else.


File: netperf.info,  Node: TCP_SENDFILE,  Next: UDP_STREAM,  Prev: TCP_MAERTS,  Up: Options common to TCP UDP and SCTP tests

5.2.3 TCP_SENDFILE
------------------

The TCP_SENDFILE test is "just like" a *Note TCP_STREAM:: test except
netperf the platform's `sendfile()' call instead of calling `send()'.
Often this results in a "zero-copy" operation where data is sent
directly from the filesystem buffer cache.  This _should_ result in
lower CPU utilization and possibly higher throughput.  If it does not,
then you may want to contact your vendor(s) because they have a problem
on their hands.

   Zero-copy mechanisms may also alter the characteristics (size and
number of buffers per) of packets passed to the NIC.  In many stacks,
when a copy is performed, the stack can "reserve" space at the
beginning of the destination buffer for things like TCP, IP and Link
headers.  This then has the packet contained in a single buffer which
can be easier to DMA to the NIC.  When no copy is performed, there is
no opportunity to reserve space for headers and so a packet will be
contained in two or more buffers.

   The *Note global `-F' option: Global Options. is required for this
test and it must specify a file of at least the size of the send ring
(*Note the global `-W' option: Global Options.) multiplied by the send
size (*Note the test-specific `-m' option: Options common to TCP UDP
and SCTP tests.).  All other TCP-specific options are available and
optional.

   In this first example:
     $ netperf -H lag -F ../src/netperf -t TCP_SENDFILE -- -s 128K -S 128K
     TCP SENDFILE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to lag.hpl.hp.com (15.4.89.214) port 0 AF_INET
     alloc_sendfile_buf_ring: specified file too small.
     file must be larger than send_width * send_size

   we see what happens when the file is too small.  Here:

     $ ../src/netperf -H lag -F /boot/vmlinuz-2.6.8-1-686 -t TCP_SENDFILE -- -s 128K -S 128K
     TCP SENDFILE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to lag.hpl.hp.com (15.4.89.214) port 0 AF_INET
     Recv   Send    Send
     Socket Socket  Message  Elapsed
     Size   Size    Size     Time     Throughput
     bytes  bytes   bytes    secs.    10^6bits/sec

     131072 221184 221184    10.02      81.83

   we resolve that issue by selecting a larger file.


File: netperf.info,  Node: UDP_STREAM,  Next: XTI_TCP_STREAM,  Prev: TCP_SENDFILE,  Up: Options common to TCP UDP and SCTP tests

5.2.4 UDP_STREAM
----------------

A UDP_STREAM test is similar to a *Note TCP_STREAM:: test except UDP is
used as the transport rather than TCP.

   A UDP_STREAM test has no end-to-end flow control - UDP provides none
and neither does netperf.  However, if you wish, you can configure
netperf with `--enable-intervals=yes' to enable the global command-line
`-b' and `-w' options to pace bursts of traffic onto the network.

   This has a number of implications.

   The biggest of these implications is the data which is sent might not
be received by the remote.  For this reason, the output of a UDP_STREAM
test shows both the sending and receiving throughput.  On some
platforms, it may be possible for the sending throughput to be reported
as a value greater than the maximum rate of the link.  This is common
when the CPU(s) are faster than the network and there is no
"intra-stack" flow-control.

   Here is an example of a UDP_STREAM test between two systems connected
by a 10 Gigabit Ethernet link:
     $ netperf -t UDP_STREAM -H 192.168.2.125 -- -m 32768
     UDP UNIDIRECTIONAL SEND TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.2.125 (192.168.2.125) port 0 AF_INET
     Socket  Message  Elapsed      Messages
     Size    Size     Time         Okay Errors   Throughput
     bytes   bytes    secs            #      #   10^6bits/sec

     124928   32768   10.00      105672      0    2770.20
     135168           10.00      104844           2748.50

   The first line of numbers are statistics from the sending (netperf)
side. The second line of numbers are from the receiving (netserver)
side.  In this case, 105672 - 104844 or 828 messages did not make it
all the way to the remote netserver process.

   If the value of the `-m' option is larger than the local send socket
buffer size (`-s' option) netperf will likely abort with an error
message about how the send call failed:

     netperf -t UDP_STREAM -H 192.168.2.125
     UDP UNIDIRECTIONAL SEND TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.2.125 (192.168.2.125) port 0 AF_INET
     udp_send: data send error: Message too long

   If the value of the `-m' option is larger than the remote socket
receive buffer, the reported receive throughput will likely be zero as
the remote UDP will discard the messages as being too large to fit into
the socket buffer.

     $ netperf -t UDP_STREAM -H 192.168.2.125 -- -m 65000 -S 32768
     UDP UNIDIRECTIONAL SEND TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.2.125 (192.168.2.125) port 0 AF_INET
     Socket  Message  Elapsed      Messages
     Size    Size     Time         Okay Errors   Throughput
     bytes   bytes    secs            #      #   10^6bits/sec

     124928   65000   10.00       53595      0    2786.99
      65536           10.00           0              0.00

   The example above was between a pair of systems running a "Linux"
kernel. Notice that the remote Linux system returned a value larger
than that passed-in to the `-S' option.  In fact, this value was larger
than the message size set with the `-m' option.  That the remote socket
buffer size is reported as 65536 bytes would suggest to any sane person
that a message of 65000 bytes would fit, but the socket isn't _really_
65536 bytes, even though Linux is telling us so.  Go figure.


File: netperf.info,  Node: XTI_TCP_STREAM,  Next: XTI_UDP_STREAM,  Prev: UDP_STREAM,  Up: Options common to TCP UDP and SCTP tests

5.2.5 XTI_TCP_STREAM
--------------------

An XTI_TCP_STREAM test is simply a *Note TCP_STREAM:: test using the XTI
rather than BSD Sockets interface.  The test-specific `-X <devspec>'
option can be used to specify the name of the local and/or remote XTI
device files, which is required by the `t_open()' call made by netperf
XTI tests.

   The XTI_TCP_STREAM test is only present if netperf was configured
with `--enable-xti=yes'.  The remote netserver must have also been
configured with `--enable-xti=yes'.


File: netperf.info,  Node: XTI_UDP_STREAM,  Next: SCTP_STREAM,  Prev: XTI_TCP_STREAM,  Up: Options common to TCP UDP and SCTP tests

5.2.6 XTI_UDP_STREAM
--------------------

An XTI_UDP_STREAM test is simply a *Note UDP_STREAM:: test using the XTI
rather than BSD Sockets Interface.  The test-specific `-X <devspec>'
option can be used to specify the name of the local and/or remote XTI
device files, which is required by the `t_open()' call made by netperf
XTI tests.

   The XTI_UDP_STREAM test is only present if netperf was configured
with `--enable-xti=yes'. The remote netserver must have also been
configured with `--enable-xti=yes'.


File: netperf.info,  Node: SCTP_STREAM,  Next: DLCO_STREAM,  Prev: XTI_UDP_STREAM,  Up: Options common to TCP UDP and SCTP tests

5.2.7 SCTP_STREAM
-----------------

An SCTP_STREAM test is essentially a *Note TCP_STREAM:: test using the
SCTP rather than TCP.  The `-D' option will set SCTP_NODELAY, which is
much like the TCP_NODELAY option for TCP.  The `-C' option is not
applicable to an SCTP test as there is no corresponding SCTP_CORK
option.  The author is still figuring-out what the test-specific `-N'
option does :)

   The SCTP_STREAM test is only present if netperf was configured with
`--enable-sctp=yes'. The remote netserver must have also been
configured with `--enable-sctp=yes'.


File: netperf.info,  Node: DLCO_STREAM,  Next: DLCL_STREAM,  Prev: SCTP_STREAM,  Up: Options common to TCP UDP and SCTP tests

5.2.8 DLCO_STREAM
-----------------

A DLPI Connection Oriented Stream (DLCO_STREAM) test is very similar in
concept to a *Note TCP_STREAM:: test.  Both use reliable,
connection-oriented protocols.  The DLPI test differs from the TCP test
in that its protocol operates only at the link-level and does not
include TCP-style segmentation and reassembly.  This last difference
means that the value  passed-in  with the `-m' option must be less than
the interface MTU.  Otherwise, the `-m' and `-M' options are just like
their TCP/UDP/SCTP counterparts.

   Other DLPI-specific options include:

`-D <devspec>'
     This option is used to provide the fully-qualified names for the
     local and/or remote DPLI device files.  The syntax is otherwise
     identical to that of a "sizespec".

`-p <ppaspec>'
     This option is used to specify the local and/or remote DLPI PPA(s).
     The PPA is used to identify the interface over which traffic is to
     be sent/received. The syntax of a "ppaspec" is otherwise the same
     as a "sizespec".

`-s sap'
     This option specifies the 802.2 SAP for the test.  A SAP is
     somewhat like either the port field of a TCP or UDP header or the
     protocol field of an IP header.  The specified SAP should not
     conflict with any other active SAPs on the specified PPA's (`-p'
     option).

`-w <sizespec>'
     This option specifies the local send and receive window sizes in
     units of frames on those platforms which support setting such
     things.

`-W <sizespec>'
     This option specifies the remote send and receive window sizes in
     units of frames on those platforms which support setting such
     things.

   The DLCO_STREAM test is only present if netperf was configured with
`--enable-dlpi=yes'. The remote netserver must have also been
configured with `--enable-dlpi=yes'.


File: netperf.info,  Node: DLCL_STREAM,  Next: STREAM_STREAM,  Prev: DLCO_STREAM,  Up: Options common to TCP UDP and SCTP tests

5.2.9 DLCL_STREAM
-----------------

A DLPI ConnectionLess Stream (DLCL_STREAM) test is analogous to a *Note
UDP_STREAM:: test in that both make use of unreliable/best-effort,
connection-less transports.  The DLCL_STREAM test differs from the
*Note UDP_STREAM:: test in that the message size (`-m' option) must
always be less than the link MTU as there is no IP-like fragmentation
and reassembly available and netperf does not presume to provide one.

   The test-specific command-line options for a DLCL_STREAM test are the
same as those for a *Note DLCO_STREAM:: test.

   The DLCL_STREAM test is only present if netperf was configured with
`--enable-dlpi=yes'. The remote netserver must have also been
configured with `--enable-dlpi=yes'.


File: netperf.info,  Node: STREAM_STREAM,  Next: DG_STREAM,  Prev: DLCL_STREAM,  Up: Options common to TCP UDP and SCTP tests

5.2.10 STREAM_STREAM
--------------------

A Unix Domain Stream Socket Stream test (STREAM_STREAM) is similar in
concept to a *Note TCP_STREAM:: test, but using Unix Domain sockets.
It is, naturally, limited to intra-machine traffic.  A STREAM_STREAM
test shares the `-m', `-M', `-s' and `-S' options of the other _STREAM
tests.  In a STREAM_STREAM test the `-p' option sets the directory in
which the pipes will be created rather than setting a port number.  The
default is to create the pipes in the system default for the
`tempnam()' call.

   The STREAM_STREAM test is only present if netperf was configured with
`--enable-unix=yes'. The remote netserver must have also been
configured with `--enable-unix=yes'.


File: netperf.info,  Node: DG_STREAM,  Prev: STREAM_STREAM,  Up: Options common to TCP UDP and SCTP tests

5.2.11 DG_STREAM
----------------

A Unix Domain Datagram Socket Stream test (SG_STREAM) is very much like
a *Note TCP_STREAM:: test except that message boundaries are preserved.
In this way, it may also be considered similar to certain flavors of
SCTP test which can also preserve message boundaries.

   All the options of a *Note STREAM_STREAM:: test are applicable to a
DG_STREAM test.

   The DG_STREAM test is only present if netperf was configured with
`--enable-unix=yes'. The remote netserver must have also been
configured with `--enable-unix=yes'.


File: netperf.info,  Node: Using Netperf to Measure Request/Response,  Next: Using Netperf to Measure Aggregate Performance,  Prev: Using Netperf to Measure Bulk Data Transfer,  Up: Top

6 Using Netperf to Measure Request/Response
*******************************************

Request/response performance is often overlooked, yet it is just as
important as bulk-transfer performance.  While things like larger
socket buffers and TCP windows can cover a multitude of latency and
even path-length sins, they cannot easily hide from a request/response
test.  The convention for a request/response test is to have a _RR
suffix.  There are however a few "request/response" tests that have
other suffixes.

   A request/response test, particularly synchronous, one transaction at
at time test such as those found in netperf, is particularly sensitive
to the path-length of the networking stack.  An _RR test can also
uncover those platforms where the NIC's are strapped by default with
overbearing interrupt avoidance settings in an attempt to increase the
bulk-transfer performance (or rather, decrease the CPU utilization of a
bulk-transfer test).  This sensitivity is most acute for small request
and response sizes, such as the single-byte default for a netperf _RR
test.

   While a bulk-transfer test reports its results in units of bits or
bytes transfered per second, a mumble_RR test reports transactions per
second where a transaction is defined as the completed exchange of a
request and a response.  One can invert the transaction rate to arrive
at the average round-trip latency.  If one is confident about the
symmetry of the connection, the average one-way latency can be taken as
one-half the average round-trip latency.  Netperf does not do either of
these on its own but leaves them as exercises to the benchmarker.

* Menu:

* Issues in Request/Response::
* Options Common to TCP UDP and SCTP _RR tests::


File: netperf.info,  Node: Issues in Request/Response,  Next: Options Common to TCP UDP and SCTP _RR tests,  Prev: Using Netperf to Measure Request/Response,  Up: Using Netperf to Measure Request/Response

6.1 Issues in Reqeust/Response
==============================

Most if not all the *Note Issues in Bulk Transfer:: apply to
request/response.  The issue of round-trip latency is even more
important as netperf generally only has one transaction outstanding at
a time.

   A single instance of a one transaction outstanding _RR test should
_never_ completely saturate the CPU of a system.  If testing between
otherwise evenly matched systems, the symmetric nature of a _RR test
with equal request and response sizes should result in equal CPU
loading on both systems. However, this may not hold true on MP systems,
particularly if one CPU binds the netperf and netserver differently via
the global `-T' option.

   For smaller request and response sizes packet loss is a bigger issue
as there is no opportunity for a "fast retransmit" or retransmission
prior to a retransmission timer expiring.

   Certain NICs have ways to minimize the number of interrupts sent to
the host.  If these are strapped badly they can significantly reduce
the performance of something like a single-byte request/response test.
Such setups are distinguised by seriously low reported CPU utilization
and what seems like a low (even if in the thousands) transaction per
second rate.  Also, if you run such an OS/driver combination on faster
or slower hardware and do not see a corresponding change in the
transaction rate, chances are good that the drvier is strapping the NIC
with aggressive interrupt avoidance settings.  Good for bulk
throughput, but bad for latency.

   Some drivers may try to automagically adjust the interrupt avoidance
settings.  If they are not terribly good at it, you will see
considerable run-to-run variation in reported transaction rates.
Particularly if you "mix-up" _STREAM and _RR tests.


File: netperf.info,  Node: Options Common to TCP UDP and SCTP _RR tests,  Prev: Issues in Request/Response,  Up: Using Netperf to Measure Request/Response

6.2 Options Common to TCP UDP and SCTP _RR tests
================================================

Many "test-specific" options are actually common across the different
tests.  For those tests involving TCP, UDP and SCTP, whether using the
BSD Sockets or the XTI interface those common options include:

`-h'
     Display the test-suite-specific usage string and exit.  For a TCP_
     or UDP_ test this will be the usage string from the source file
     `nettest_bsd.c'.  For an XTI_ test, this will be the usage string
     from the source file `src/nettest_xti.c'.  For an SCTP test, this
     will be the usage string from the source file `src/nettest_sctp.c'.

`-H <optionspec>'
     Normally, the remote hostname|IP and address family information is
     inherited from the settings for the control connection (eg global
     command-line `-H', `-4' and/or `-6' options.  The test-specific
     `-H' will override those settings for the data (aka test)
     connection only.  Settings for the control connection are left
     unchanged.  This might be used to cause the control and data
     connections to take different paths through the network.

`-L <optionspec>'
     The test-specific `-L' option is identical to the test-specific
     `-H' option except it affects the local hostname|IP and address
     family information.  As with its global command-line counterpart,
     this is generally only useful when measuring though those evil,
     end-to-end breaking things called firewalls.

`-P <optionspec>'
     Set the local and/or remote port numbers for the data connection.

`-r <sizespec>'
     This option sets the request (first value) and/or response (second
     value) sizes for an _RR test. By default the units are bytes, but a
     suffix of "G," "M," or "K" will specify the units to be 2^30 (GB),
     2^20 (MB) or 2^10 (KB) respectively.  A suffix of "g," "m" or "k"
     will specify units of 10^9, 10^6 or 10^3 bytes respectively. For
     example:
          `-r 128,16K'
     Will set the request size to 128 bytes and the response size to 16
     KB or 16384 bytes. [Default: 1 - a single-byte request and
     response ]

`-s <sizespec>'
     This option sets the local send and receive socket buffer sizes for
     the data connection to the value(s) specified.  Often, this will
     affect the advertised and/or effective TCP or other window, but on
     some platforms it may not. By default the units are bytes, but a
     suffix of "G," "M," or "K" will specify the units to be 2^30 (GB),
     2^20 (MB) or 2^10 (KB) respectively.  A suffix of "g," "m" or "k"
     will specify units of 10^9, 10^6 or 10^3 bytes respectively. For
     example:
          `-s 128K'
     Will request the local send and receive socket buffer sizes to be
     128KB or 131072 bytes.

     While the historic expectation is that setting the socket buffer
     size has a direct effect on say the TCP window, today that may not
     hold true for all stacks.  When running under Windows a value of 0
     may be used which will be an indication to the stack the user
     wants to enable a form of copy avoidance. [Default: -1 - use the
     system's default socket buffer sizes]

`-S <sizespec>'
     This option sets the remote send and/or receive socket buffer sizes
     for the data connection to the value(s) specified.  Often, this
     will affect the advertised and/or effective TCP or other window,
     but on some platforms it may not. By default the units are bytes,
     but a suffix of "G," "M," or "K" will specify the units to be 2^30
     (GB), 2^20 (MB) or 2^10 (KB) respectively.  A suffix of "g," "m"
     or "k" will specify units of 10^9, 10^6 or 10^3 bytes respectively.
     For example:
          `-s 128K'
     Will request the local send and receive socket buffer sizes to be
     128KB or 131072 bytes.

     While the historic expectation is that setting the socket buffer
     size has a direct effect on say the TCP window, today that may not
     hold true for all stacks.  When running under Windows a value of 0
     may be used which will be an indication to the stack the user
     wants to enable a form of copy avoidance.  [Default: -1 - use the
     system's default socket buffer sizes]

`-4'
     Set the local and remote address family for the data connection to
     AF_INET - ie use IPv4 addressing only.  Just as with their global
     command-line counterparts the last of the `-4', `-6', `-H' or `-L'
     option wins for their respective address families.

`-6'
     This option is identical to its `-4' cousin, but requests IPv6
     addresses for the local and remote ends of the data connection.


* Menu:

* TCP_RR::
* TCP_CC::
* TCP_CRR::
* UDP_RR::
* XTI_TCP_RR::
* XTI_TCP_CC::
* XTI_TCP_CRR::
* XTI_UDP_RR::
* DLCL_RR::
* DLCO_RR::
* SCTP_RR::


File: netperf.info,  Node: TCP_RR,  Next: TCP_CC,  Prev: Options Common to TCP UDP and SCTP _RR tests,  Up: Options Common to TCP UDP and SCTP _RR tests

6.2.1 TCP_RR
------------

A TCP_RR (TCP Request/Response) test is requested by passing a value of
"TCP_RR" to the global `-t' command-line option.  A TCP_RR test can be
though-of as a user-space to user-space `ping' with no think time - it
is a synchronous, one transaction at a time, request/response test.

   The transaction rate is the number of complete transactions exchanged
divided by the length of time it took to perform those transactions.

   If the two Systems Under Test are otherwise identical, a TCP_RR test
with the same request and response size should be symmetric - it should
not matter which way the test is run, and the CPU utilization measured
should be virtually the same on each system.  If not, it suggests that
the CPU utilization mechanism being used may have some, well, issues
measuring CPU utilization completely and accurately.

   Time to establish the TCP connection is not counted in the result.
If you want connection setup overheads included, you should consider the
TCP_CC or TCP_CRR tests.

   If specifying the `-D' option to set TCP_NODELAY and disable the
Nagle Algorithm increases the transaction rate reported by a TCP_RR
test, it implies the stack(s) over which the TCP_RR test is running
have a broken implementation of the Nagle Algorithm.  Likely as not
they are interpreting Nagle on a segment by segment basis rather than a
user send by user send basis.  You should contact your stack vendor(s)
to report the problem to them.

   Here is an example of two systems running a basic TCP_RR test over a
10 Gigabit Ethernet link:

     netperf -t TCP_RR -H 192.168.2.125
     TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.2.125 (192.168.2.125) port 0 AF_INET
     Local /Remote
     Socket Size   Request  Resp.   Elapsed  Trans.
     Send   Recv   Size     Size    Time     Rate
     bytes  Bytes  bytes    bytes   secs.    per sec

     16384  87380  1        1       10.00    29150.15
     16384  87380

   In this example the request and response sizes were one byte, the
socket buffers were left at their defaults, and the test ran for all of
10 seconds.  The transaction per second rate was rather good :)


File: netperf.info,  Node: TCP_CC,  Next: TCP_CRR,  Prev: TCP_RR,  Up: Options Common to TCP UDP and SCTP _RR tests

6.2.2 TCP_CC
------------

A TCP_CC (TCP Connect/Close) test is requested by passing a value of
"TCP_CC" to the global `-t' option.  A TCP_CC test simply measures how
fast the pair of systems can open and close connections between one
another in a synchronous (one at a time) manner.  While this is
considered an _RR test, no request or response is exchanged over the
connection.

   The issue of TIME_WAIT reuse is an important one for a TCP_CC test.
Basically, TIME_WAIT reuse is when a pair of systems churn through
connections fast enough that they wrap the 16-bit port number space in
less time than the length of the TIME_WAIT state.  While it is indeed
theoretically possible to "reuse" a connection in TIME_WAIT, the
conditions under which such reuse is possible are rather rare.  An
attempt to reuse a connection in TIME_WAIT can result in a non-trivial
delay in connection establishment.

   Basically, any time the connection churn rate approaches:

   Sizeof(clientportspace) / Lengthof(TIME_WAIT)

   there is the risk of TIME_WAIT reuse.  To minimize the chances of
this happening, netperf will by default select its own client port
numbers from the range of 5000 to 65535.  On systems with a 60 second
TIME_WAIT state, this should allow roughly 1000 transactions per
second.  The size of the client port space used by netperf can be
controlled via the test-specific `-p' option, which takes a "sizespec"
as a value setting the minimum (first value) and maximum (second value)
port numbers used by netperf at the client end.

   Since no requests or responses are exchanged during a TCP_CC test,
only the `-H', `-L', `-4' and `-6' of the "common" test-specific
options are likely to have an effect, if any, on the results.  The `-s'
and `-S' options _may_ have some effect if they alter the number and/or
type of options carried in the TCP SYNchronize segments.  The `-P'  and
`-r' options are utterly ignored.

   Since connection establishment and tear-down for TCP is not
symmetric, a TCP_CC test is not symmetric in its loading of the two
systems under test.


File: netperf.info,  Node: TCP_CRR,  Next: UDP_RR,  Prev: TCP_CC,  Up: Options Common to TCP UDP and SCTP _RR tests

6.2.3 TCP_CRR
-------------

The TCP Connect/Request/Response (TCP_CRR) test is requested by passing
a value of "TCP_CRR" to the global `-t' command-line option.  A TCP_RR
test is like a merger of a TCP_RR and TCP_CC test which measures the
performance of establishing a connection, exchanging a single
request/response transaction, and tearing-down that connection.  This
is very much like what happens in an HTTP 1.0 or HTTP 1.1 connection
when HTTP Keepalives are not used.  In fact, the TCP_CRR test was added
to netperf to simulate just that.

   Since a request and response are exchanged the `-r', `-s' and `-S'
options can have an effect on the performance.

   The issue of TIME_WAIT reuse exists for the TCP_CRR test just as it
does for the TCP_CC test.  Similarly, since connection establishment
and tear-down is not symmetric, a TCP_CRR test is not symmetric even
when the request and response sizes are the same.


File: netperf.info,  Node: UDP_RR,  Next: XTI_TCP_RR,  Prev: TCP_CRR,  Up: Options Common to TCP UDP and SCTP _RR tests

6.2.4 UDP_RR
------------

A UDP Request/Response (UDP_RR) test is requested by passing a value of
"UDP_RR" to a global `-t' option.  It is very much the same as a TCP_RR
test except UDP is used rather than TCP.

   UDP does not provide for retransmission of lost UDP datagrams, and
netperf does not add anything for that either.  This means that if
_any_ request or response is lost, the exchange of requests and
responses will stop from that point until the test timer expires.
Netperf will not really "know" this has happened - the only symptom
will be a low transaction per second rate.

   The netperf side of a UDP_RR test will call `connect()' on its data
socket and thenceforth use the `send()' and `recv()' socket calls.  The
netserver side of a UDP_RR test will not call `connect()' and will use
`recvfrom()' and `sendto()' calls.  This means that even if the request
and response sizes are the same, a UDP_RR test is _not_ symmetric in
its loading of the two systems under test.

   Here is an example of a UDP_RR test between two otherwise identical
two-CPU systems joined via a 1 Gigabit Ethernet network:

     $ netperf -T 1 -H 192.168.1.213 -t UDP_RR -c -C
     UDP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.1.213 (192.168.1.213) port 0 AF_INET
     Local /Remote
     Socket Size   Request Resp.  Elapsed Trans.   CPU    CPU    S.dem   S.dem
     Send   Recv   Size    Size   Time    Rate     local  remote local   remote
     bytes  bytes  bytes   bytes  secs.   per sec  % I    % I    us/Tr   us/Tr

     65535  65535  1       1      10.01   15262.48   13.90  16.11  18.221  21.116
     65535  65535

   This example includes the `-c' and `-C' options to enable CPU
utilization reporting and shows the asymmetry in CPU loading.  The `-T'
option was used to make sure netperf and netserver ran on a given CPU
and did not move around during the test.


File: netperf.info,  Node: XTI_TCP_RR,  Next: XTI_TCP_CC,  Prev: UDP_RR,  Up: Options Common to TCP UDP and SCTP _RR tests

6.2.5 XTI_TCP_RR
----------------

An XTI_TCP_RR test is essentially the same as a *Note TCP_RR:: test only
using the XTI rather than BSD Sockets interface. It is requested by
passing a value of "XTI_TCP_RR" to the `-t' global command-line option.

   The test-specific options for an XTI_TCP_RR test are the same as
those for a TCP_RR test with the addition of the `-X <devspec>' option
to specify the names of the local and/or remote XTI device file(s).


File: netperf.info,  Node: XTI_TCP_CC,  Next: XTI_TCP_CRR,  Prev: XTI_TCP_RR,  Up: Options Common to TCP UDP and SCTP _RR tests

6.2.6 XTI_TCP_CC
----------------


File: netperf.info,  Node: XTI_TCP_CRR,  Next: XTI_UDP_RR,  Prev: XTI_TCP_CC,  Up: Options Common to TCP UDP and SCTP _RR tests

6.2.7 XTI_TCP_CRR
-----------------


File: netperf.info,  Node: XTI_UDP_RR,  Next: DLCL_RR,  Prev: XTI_TCP_CRR,  Up: Options Common to TCP UDP and SCTP _RR tests

6.2.8 XTI_UDP_RR
----------------

An XTI_UDP_RR test is essentially the same as a UDP_RR test only using
the XTI rather than BSD Sockets interface.  It is requested by passing
a value of "XTI_UDP_RR" to the `-t' global command-line option.

   The test-specific options for an XTI_UDP_RR test are the same as
those for a UDP_RR test with the addition of the `-X <devspec>' option
to specify the name of the local and/or remote XTI device file(s).


File: netperf.info,  Node: DLCL_RR,  Next: DLCO_RR,  Prev: XTI_UDP_RR,  Up: Options Common to TCP UDP and SCTP _RR tests

6.2.9 DLCL_RR
-------------


File: netperf.info,  Node: DLCO_RR,  Next: SCTP_RR,  Prev: DLCL_RR,  Up: Options Common to TCP UDP and SCTP _RR tests

6.2.10 DLCO_RR
--------------


File: netperf.info,  Node: SCTP_RR,  Prev: DLCO_RR,  Up: Options Common to TCP UDP and SCTP _RR tests

6.2.11 SCTP_RR
--------------


File: netperf.info,  Node: Using Netperf to Measure Aggregate Performance,  Next: Using Netperf to Measure Bidirectional Transfer,  Prev: Using Netperf to Measure Request/Response,  Up: Top

7 Using Netperf to Measure Aggregate Performance
************************************************

*Note Netperf4: Netperf4. is the preferred benchmark to use when one
wants to measure aggregate performance because netperf has no support
for explicit synchronization of concurrent tests.

   Basically, there are two ways to measure aggregate performance with
netperf.  The first is to run multiple, concurrent netperf tests and
can be applied to any of the netperf tests.  The second is to configure
netperf with `--enable-burst' and is applicable to the TCP_RR test.

* Menu:

* Running Concurrent Netperf Tests::
* Using --enable-burst::


File: netperf.info,  Node: Running Concurrent Netperf Tests,  Next: Using --enable-burst,  Prev: Using Netperf to Measure Aggregate Performance,  Up: Using Netperf to Measure Aggregate Performance

7.1 Running Concurrent Netperf Tests
====================================

*Note Netperf4: Netperf4. is the preferred benchmark to use when one
wants to measure aggregate performance because netperf has no support
for explicit synchronization of concurrent tests.  This leaves netperf2
results vulnerable to "skew" errors.

   However, since there are times when netperf4 is unavailable it may be
necessary to run netperf. The skew error can be minimized by making use
of the confidence interval functionality.  Then one simply launches
multiple tests from the shell using a `for' loop or the like:

     for i in 1 2 3 4
     do
     netperf -t TCP_STREAM -H tardy.cup.hp.com -i 10 -P 0 &
     done

   which will run four, concurrent *Note TCP_STREAM: TCP_STREAM. tests
from the system on which it is executed to tardy.cup.hp.com.  Each
concurrent netperf will iterate 10 times thanks to the `-i' option and
will omit the test banners (option `-P') for brevity.  The output looks
something like this:

      87380  16384  16384    10.03     235.15
      87380  16384  16384    10.03     235.09
      87380  16384  16384    10.03     235.38
      87380  16384  16384    10.03     233.96

   We can take the sum of the results and be reasonably confident that
the aggregate performance was 940 Mbits/s.

   If you see warnings about netperf not achieving the confidence
intervals, the best thing to do is to increase the number of iterations
with `-i' and/or increase the run length of each iteration with `-l'.

   You can also enable local (`-c') and/or remote (`-C') CPU
utilization:

     for i in 1 2 3 4
     do
     netperf -t TCP_STREAM -H tardy.cup.hp.com -i 10 -P 0 -c -C &
     done

     87380  16384  16384    10.03       235.47   3.67     5.09     10.226  14.180
     87380  16384  16384    10.03       234.73   3.67     5.09     10.260  14.225
     87380  16384  16384    10.03       234.64   3.67     5.10     10.263  14.231
     87380  16384  16384    10.03       234.87   3.67     5.09     10.253  14.215

   If the CPU utilizations reported for the same system are the same or
very very close you can be reasonably confident that skew error is
minimized.  Presumeably one could then omit `-i' but that is not
advised, particularly when/if the CPU utilization approaches 100
percent.  In the example above we see that the CPU utilization on the
local system remains the same for all four tests, and is only off by
0.01 out of 5.09 on the remote system.

     NOTE: It is very important to rememeber that netperf is calculating
     system-wide CPU utilization.  When calculating the service demand
     (those last two columns in the output above) each netperf assumes
     it is the only thing running on the system.  This means that for
     concurrent tests the service demands reported by netperf will be
     wrong.  One has to compute service demands for concurrent tests by
     hand.

   If you wish you can add a unique, global `-B' option to each command
line to append the given string to the output:

     for i in 1 2 3 4
     do
     netperf -t TCP_STREAM -H tardy.cup.hp.com -B "this is test $i" -i 10 -P 0 &
     done

     87380  16384  16384    10.03     234.90   this is test 4
     87380  16384  16384    10.03     234.41   this is test 2
     87380  16384  16384    10.03     235.26   this is test 1
     87380  16384  16384    10.03     235.09   this is test 3

   You will notice that the tests completed in an order other than they
were started from the shell.  This underscores why there is a threat of
skew error and why netperf4 is the preferred tool for aggregate tests.
Even if you see the Netperf Contributing Editor acting to the
contrary!-)


File: netperf.info,  Node: Using --enable-burst,  Prev: Running Concurrent Netperf Tests,  Up: Using Netperf to Measure Aggregate Performance

7.2 Using -enable-burst
=======================

If one configures netperf with `--enable-burst':

     configure --enable-burst

   Then a test-specific `-b num' option is added to the *Note TCP_RR:
TCP_RR. and *Note UDP_RR: UDP_RR. tests. This option causes TCP_RR and
UDP_RR to quickly work their way up to having at least `num'
transactions in flight at one time.

   This is used as an alternative to or even in conjunction with
multiple-concurrent _RR tests.  When run with just a single instance of
netperf, increasing the burst size can determine the maximum number of
transactions per second can be serviced by a single process:

     for b in 0 1 2 4 8 16 32
     do
      netperf -v 0 -t TCP_RR -B "-b $b" -H hpcpc108 -P 0 -- -b $b
     done

     9457.59 -b 0
     9975.37 -b 1
     10000.61 -b 2
     20084.47 -b 4
     29965.31 -b 8
     71929.27 -b 16
     109718.17 -b 32

   The global `-v' and `-P' options were used to minimize the output to
the single figure of merit which in this case the transaction rate.
The global `-B' option was used to more clearly label the output, and
the test-specific `-b' option enabled by `--enable-burst' set the
number of transactions in flight at one time.

   Now, since the test-specific `-D' option was not specified to set
TCP_NODELAY, the stack was free to "bundle" requests and/or responses
into TCP segments as it saw fit, and since the default request and
response size is one byte, there could have been some considerable
bundling.  If one wants to try to achieve a closer to one-to-one
correspondence between a request and response and a TCP segment, add
the test-specific `-D' option:

     for b in 0 1 2 4 8 16 32
     do
      netperf -v 0 -t TCP_RR -B "-b $b -D" -H hpcpc108 -P 0 -- -b $b -D
     done

      8695.12 -b 0 -D
      19966.48 -b 1 -D
      20691.07 -b 2 -D
      49893.58 -b 4 -D
      62057.31 -b 8 -D
      108416.88 -b 16 -D
      114411.66 -b 32 -D

   You can see that this has a rather large effect on the reported
transaction rate.  In this particular instance, the author believes it
relates to interactions between the test and interrupt coalescing
settings in the driver for the NICs used.

     NOTE: Even if you set the `-D' option that is still not a
     guarantee that each transaction is in its own TCP segments.  You
     should get into the habit of verifying the relationship between the
     transaction rate and the packet rate via other means

   You can also combine `--enable-burst' functionality with concurrent
netperf tests.  This would then be an "aggregate of aggregates" if you
like:


     for i in 1 2 3 4
     do
      netperf -H hpcpc108 -v 0 -P 0 -i 10 -B "aggregate $i -b 8 -D" -t TCP_RR -- -b 8 -D &
     done

      46668.38 aggregate 4 -b 8 -D
      44890.64 aggregate 2 -b 8 -D
      45702.04 aggregate 1 -b 8 -D
      46352.48 aggregate 3 -b 8 -D

   Since each netperf did hit the confidence intervals, we can be
reasonably certain that the aggregate transaction per second rate was
the sum of all four concurrent tests, or something just shy of 184,000
transactions per second.  To get some idea if that was also the packet
per second rate, we could bracket that `for' loop with something to
gather statistics and run the results through beforeafter
(ftp://ftp.cup.hp.com/dist/networking/tools):

     /usr/sbin/ethtool -S eth2 > before
     for i in 1 2 3 4
     do
      netperf -H 192.168.2.108 -l 60 -v 0 -P 0 -B "aggregate $i -b 8 -D" -t TCP_RR -- -b 8 -D &
     done
     wait
     /usr/sbin/ethtool -S eth2 > after

      52312.62 aggregate 2 -b 8 -D
      50105.65 aggregate 4 -b 8 -D
      50890.82 aggregate 1 -b 8 -D
      50869.20 aggregate 3 -b 8 -D

     beforeafter before after > delta

     grep packets delta
          rx_packets: 12251544
          tx_packets: 12251550

   This example uses `ethtool' because the system being used is running
Linux.  Other platforms have other tools - for example HP-UX has
lanadmin:

     lanadmin -g mibstats <ppa>

   and of course one could instead use `netstat'.

   The `wait' is important because we are launching concurrent netperfs
in the background.  Without it, the second ethtool command would be run
before the tests finished and perhaps even before the last of them got
started!

   The sum of the reported transaction rates is 204178 over 60 seconds,
which is a total of 12250680 transactions.  Each transaction is the
exchange of a request and a response, so we multiply that by 2 to
arrive at 24501360.

   The sum of the ethtool stats is 24503094 packets which matches what
netperf was reporting very well.

   Had the request or response size differed, we would need to know how
it compared with the "MSS" for the connection.

   Just for grins, here is the excercise repeated, using `netstat'
instead of `ethtool'

     netstat -s -t > before
     for i in 1 2 3 4
     do
      netperf -l 60 -H 192.168.2.108 -v 0 -P 0 -B "aggregate $i -b 8 -D" -t TCP_RR -- -b 8 -D & done
     wait
     netstat -s -t > after

      51305.88 aggregate 4 -b 8 -D
      51847.73 aggregate 2 -b 8 -D
      50648.19 aggregate 3 -b 8 -D
      53605.86 aggregate 1 -b 8 -D

     beforeafter before after > delta

     grep segments delta
         12445708 segments received
         12445730 segments send out
         1 segments retransmited
         0 bad segments received.

   The sums are left as an excercise to the reader :)

   Things become considerably more complicated if there are non-trvial
packet losses and/or retransmissions.

   Of course all this checking is unnecessary if the test is a UDP_RR
test because UDP "never" aggregates multiple sends into the same UDP
datagram, and there are no ACKnowledgements in UDP.  The loss of a
single request or response will not bring a "burst" UDP_RR test to a
screeching halt, but it will reduce the number of transactions
outstanding at any one time.  A "burst" UDP_RR test will come to a halt
if the sum of the lost requests and responses reaches the value
specified in the test-specific `-b' option.


File: netperf.info,  Node: Using Netperf to Measure Bidirectional Transfer,  Next: Other Netperf Tests,  Prev: Using Netperf to Measure Aggregate Performance,  Up: Top

8 Using Netperf to Measure Bidirectional Transfer
*************************************************

There are two ways to use netperf to measure the perfomance of
bidirectional transfer.  The first is to run concurrent netperf tests
from the command line.  The second is to configure netperf with
`--enable-burst' and use a single instance of the *Note TCP_RR: TCP_RR.
test.

   While neither method is more "correct" than the other, each is doing
so in different ways, and that has possible implications.  For
instance, using the concurrent netperf test mechanism means that
multiple TCP connections and multiple processes are involved, whereas
using the single instance of TCP_RR there is only one TCP connection
and one process on each end.  They may behave differently, especially
on an MP system.

* Menu:

* Bidirectional Transfer with Concurrent Tests::
* Bidirectional Transfer with TCP_RR::


File: netperf.info,  Node: Bidirectional Transfer with Concurrent Tests,  Next: Bidirectional Transfer with TCP_RR,  Prev: Using Netperf to Measure Bidirectional Transfer,  Up: Using Netperf to Measure Bidirectional Transfer

8.1 Bidirectional Transfer with Concurrent Tests
================================================

If we had two hosts Fred and Ethel, we could simply run a netperf *Note
TCP_STREAM: TCP_STREAM. test on Fred pointing at Ethel, and a
concurrent netperf TCP_STREAM test on Ethel pointing at Fred, but since
there are no mechanisms to synchronize netperf tests and we would be
starting tests from two different systems, there is a considerable risk
of skew error.

   Far better would be to run simultaneous TCP_STREAM and *Note
TCP_MAERTS: TCP_MAERTS. tests from just one system, using the concepts
and procedures outlined in *Note Running Concurrent Netperf Tests:
Running Concurrent Netperf Tests. Here then is an example:

     for i in 1
     do
      netperf -H 192.168.2.108 -t TCP_STREAM -B "outbound" -i 10 -P 0 -v 0 -- -s 256K -S 256K &
      netperf -H 192.168.2.108 -t TCP_MAERTS -B "inbound"  -i 10 -P 0 -v 0 -- -s 256K -S 256K &
     done

      892.66 outbound
      891.34 inbound

   We have used a `for' loop in the shell with just one iteration
because that will be much easier to get both tests started at more or
less the same time than doing it by hand.  The global `-P' and `-v'
options are used because we aren't interested in anything other than
the throughput, and the global `-B' option is used to tag each output
so we know which was inbound and which outbound relative to the system
on which we were running netperf.  Of course that sense is switched on
the system running netserver :)  The use of the global `-i' option is
explained in *Note Running Concurrent Netperf Tests: Running Concurrent
Netperf Tests.


File: netperf.info,  Node: Bidirectional Transfer with TCP_RR,  Prev: Bidirectional Transfer with Concurrent Tests,  Up: Using Netperf to Measure Bidirectional Transfer

8.2 Bidirectional Transfer with TCP_RR
======================================

If one configures netperf with `--enable-burst' then one can use the
test-specific `-b' option to increase the number of transactions in
flight at one time.  If one also uses the -r option to make those
transactions larger the test starts to look more and more like a
bidirectional transfer than a request/response test.

   Now, the logic behing `--enable-burst' is very simple, and there are
no calls to `poll()' or `select()' which means we want to make sure
that the `send()' calls will never block, or we run the risk of
deadlock with each side stuck trying to call `send()' and neither
calling `recv()'.

   Fortunately, this is easily accomplished by setting a "large enough"
socket buffer size with the test-specific `-s' and `-S' options.
Presently this must be performed by the user.  Future versions of
netperf might attempt to do this automagically, but there are some
issues to be worked-out.

   Here then is an example of a bidirectional transfer test using
`--enable-burst' and the *Note TCP_RR: TCP_RR. test:

     netperf -t TCP_RR -H hpcpc108 -- -b 6 -r 32K -s 256K -S 256K
     TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to hpcpc108.cup.hp.com (16.89.84.108) port 0 AF_INET : first burst 6
     Local /Remote
     Socket Size   Request  Resp.   Elapsed  Trans.
     Send   Recv   Size     Size    Time     Rate
     bytes  Bytes  bytes    bytes   secs.    per sec

     524288 524288 32768    32768   10.01    3525.97
     524288 524288

   Now, at present netperf does not include a bit or byte rate in the
output of an _RR test which means we must calculate it ourselves. Each
transaction is the exchange of 32768 bytes of request and 32768 bytes
of response, or 65536 bytes.  Multiply that by 8 and we arrive at
524288 bits per transaction.  Multiply that by 3525.97 and we arrive at
1848623759 bits per second.  Since things were uniform, we can divide
that by two and arrive at roughly 924311879 bits per second each way.
That corresponds to "link-rate" for a 1 Gigiabit Ethernet which happens
to be the type of netpwrk used in the example.

   A future version of netperf may perform the calculation on behalf of
the user, but it would likely not emit it unless the user specified a
verbosity of 2 or more with the global `-v' option.


File: netperf.info,  Node: Other Netperf Tests,  Next: Address Resolution,  Prev: Using Netperf to Measure Bidirectional Transfer,  Up: Top

9 Other Netperf Tests
*********************

Apart from the typical performance tests, netperf contains some tests
which can be used to streamline measurements and reporting.  These
include CPU rate calibration (present) and host identification (future
enhancement).

* Menu:

* CPU rate calibration::


File: netperf.info,  Node: CPU rate calibration,  Prev: Other Netperf Tests,  Up: Other Netperf Tests

9.1 CPU rate calibration
========================

Some of the CPU utilization measurement mechanisms of netperf work by
comparing the rate at which some counter increments when the system is
idle with the rate at which that same counter increments when the
system is running a netperf test.  The ratio of those rates is used to
arrive at a CPU utilization percentage.

   This means that netperf must know the rate at which the counter
increments when the system is presumed to be "idle."  If it does not
know the rate, netperf will measure it before starting a data transfer
test.  This calibration step takes 40 seconds for each of the local or
remote ystems, and if repeated for each netperf test would make taking
repeated measurements rather slow.

   Thus, the netperf CPU utilization options `-c' and and `-C' can take
an optional calibration value.  This value is used as the "idle rate"
and the calibration step is not performed. To determine the idle rate,
netperf can be used to run special tests which only report the value of
the calibration - they are the LOC_CPU and REM_CPU tests.  These return
the calibration value for the local and remote system respectively.  A
common way to use these tests is to store their results into an
environment variable and use that in subsequent netperf commands:

     LOC_RATE=`netperf -t LOC_CPU`
     REM_RATE=`netperf -H <remote> -t REM_CPU`
     netperf -H <remote> -c $LOC_RATE -C $REM_RATE ... -- ...
     ...
     netperf -H <remote> -c $LOC_RATE -C $REM_RATE ... -- ...

   If you are going to use netperf to measure aggregate results, it is
important to use the LOC_CPU and REM_CPU tests to get the calibration
values first to avoid issues with some of the aggregate netperf tests
transferring data while others are "idle" and getting bogus calibration
values.  When running aggregate tests, it is very important to remember
that any one instance of netperf does not know about the other
instances of netperf.  It will report global CPU utilization and will
calculate service demand believing it was the only thing causing that
CPU utilization.  So, you can use the CPU utilization reported by
netperf in an aggregate test, but you have to calculate service demands
by hand.


File: netperf.info,  Node: Address Resolution,  Next: Enhancing Netperf,  Prev: Other Netperf Tests,  Up: Top

10 Address Resolution
*********************

Netperf versions 2.4.0 and later have merged IPv4 and IPv6 tests so the
functionality of the tests in `src/nettest_ipv6.c' has been subsumed
into the tests in `src/nettest_bsd.c'  This has been accomplished in
part by switching from `gethostbyname()'to `getaddrinfo()' exclusively.
While it was theoretically possible to get multiple results for a
hostname from `gethostbyname()' it was generally unlikely and netperf's
ignoring of the second and later results was not much of an issue.

   Now with `getaddrinfo' and particularly with AF_UNSPEC it is
increasingly likely that a given hostname will have multiple associated
addresses.  The `establish_control()' routine of `src/netlib.c' will
indeed attempt to chose from among all the matching IP addresses when
establishing the control connection.  Netperf does not _really_ care if
the control connection is IPv4 or IPv6 or even mixed on either end.

   However, the individual tests still ass-u-me that the first result in
the address list is the one to be used.  Whether or not this will
turn-out to be an issue has yet to be determined.

   If you do run into problems with this, the easiest workaround is to
specify IP addresses for the data connection explicitly in the
test-specific `-H' and `-L' options.  At some point, the netperf tests
_may_ try to be more sophisticated in their parsing of returns from
`getaddrinfo()' - straw-man patches to <netperf-feedback@netperf.org>
would of course be most welcome :)

   Netperf has leveraged code from other open-source projects with
amenable licensing to provide a replacement `getaddrinfo()' call on
those platforms where the `configure' script believes there is no
native getaddrinfo call.  As of this writing, the replacement
`getaddrinfo()' as been tested on HP-UX 11.0 and then presumed to run
elsewhere.


File: netperf.info,  Node: Enhancing Netperf,  Next: Netperf4,  Prev: Address Resolution,  Up: Top

11 Enhancing Netperf
********************

Netperf is constantly evolving.  If you find you want to make
enhancements to netperf, by all means do so.  If you wish to add a new
"suite" of tests to netperf the general idea is to

  1. Add files `src/nettest_mumble.c' and `src/nettest_mumble.h' where
     mumble is replaced with something meaningful for the test-suite.

  2. Add support for an apropriate `--enable-mumble' option in
     `configure.ac'.

  3. Edit `src/netperf.c', `netsh.c', and `netserver.c' as required,
     using #ifdef WANT_MUMBLE.

  4. Compile and test

   If you wish to submit your changes for possible inclusion into the
mainline sources, please try to base your changes on the latest
available sources. (*Note Getting Netperf Bits::.) and then send email
describing the changes at a high level to
<netperf-feedback@netperf.org> or perhaps <netperf-talk@netperf.org>.
If the concensus is positive, then sending context `diff' results to
<netperf-feedback@netperf.org> is the next step.  From that point, it
is a matter of pestering the Netperf Contributing Editor until he gets
the changes incorporated :)


File: netperf.info,  Node: Netperf4,  Next: Concept Index,  Prev: Enhancing Netperf,  Up: Top

12 Netperf4
***********

Netperf4 is the shorthand name given to version 4.X.X of netperf.  This
is really a separate benchmark more than a newer version of netperf,
but it is a decendant of netperf so the netperf name is kept.  The
facitious way to describe netperf4 is to say it is the
egg-laying-wolly-milk-pig version of netperf :)  The more respectful
way to describe it is to say it is the version of netperf with support
for synchronized, multiple-thread, multiple-test, multiple-system,
network-oriented benchmarking.

   Netperf4 is still undergoing rapid evolution. Those wishing to work
with or on netperf4 are encouraged to join the netperf-dev
(http://www.netperf.org/cgi-bin/mailman/listinfo/netperf-dev) mailing
list and/or peruse the current sources
(http://www.netperf.org/svn/netperf4/trunk).


File: netperf.info,  Node: Concept Index,  Next: Option Index,  Prev: Netperf4,  Up: Top

Concept Index
*************