diff options
Diffstat (limited to 'README.hpux')
-rw-r--r-- | README.hpux | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/README.hpux b/README.hpux new file mode 100644 index 0000000..7818449 --- /dev/null +++ b/README.hpux @@ -0,0 +1,31 @@ +A note about CPU utilization... + +For HP-UX 11.0 <= system < 11.23 the configure script will select the +"pstat" CPU utilization mechanism. This mechanism is the familiar +HP-UX idle counter mechanism (for all incense and porpoises) and +requires calibration. See src/netcpu_pstat.c for all the details. + +For HP-UX 11.23 >= system, the configure script will select the +"pstatnew" CPU utilization mechanism. 11.23 adds cycle counts for +user, kernel and interrupt modes to the idle cycle counter. As such, +it _should_ be possible to simply take the sum of the four and the +fractions and know how much time was spent in each mode. +HOWEVER... there is a bug in the accounting for interrupt cycles, +where interrupt cycles go missing. SOOO, since there is an accurate +way to know what the total number of cycles should have been over the +interval, and we know (ass-u-me) that the idle cycle counter is good +(since the pstat mechanism has tested that one OK), we will take the +ratio of idle to total cycles to compute CPU util. + +We will still calculate fractions for user, kernel and interrupt, and +report them in debug (-d) output, but with a warning for interrupt +time. See src/netcpu_pstatnew.c for all the details. + +Up through HP-UX 11.23 (aka 11iV2) if you enable burst mode, and +happen to send sub-MSS requests and/or responses you _cannot_ assume +that the packet per second rate on the wire will match the transaction +per second rate reported by netperf, even if you set TCP_NODELAY with +the test-specific -D option. The HP-UX 11.X TCP stack likely will be +generating some immediate 'standalone' ACKnowledgements which may not +be generated by other stacks. This has been reported to the HP-UX TCP +folks, and an announcement will be made when that issue is resolved. |