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#!/usr/bin/python
# @lint-avoid-python-3-compatibility-imports
#
# biosnoop Trace block device I/O and print details including issuing PID.
# For Linux, uses BCC, eBPF.
#
# This uses in-kernel eBPF maps to cache process details (PID and comm) by I/O
# request, as well as a starting timestamp for calculating I/O latency.
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 16-Sep-2015 Brendan Gregg Created this.
# 11-Feb-2016 Allan McAleavy updated for BPF_PERF_OUTPUT
from __future__ import print_function
from bcc import BPF
import re
import argparse
# arguments
examples = """examples:
./biosnoop # trace all block I/O
./biosnoop -Q # include OS queued time
"""
parser = argparse.ArgumentParser(
description="Trace block I/O",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-Q", "--queue", action="store_true",
help="include OS queued time")
parser.add_argument("--ebpf", action="store_true",
help=argparse.SUPPRESS)
args = parser.parse_args()
debug = 0
# define BPF program
bpf_text="""
#include <uapi/linux/ptrace.h>
#include <linux/blkdev.h>
// for saving the timestamp and __data_len of each request
struct start_req_t {
u64 ts;
u64 data_len;
};
struct val_t {
u64 ts;
u32 pid;
char name[TASK_COMM_LEN];
};
struct data_t {
u32 pid;
u64 rwflag;
u64 delta;
u64 qdelta;
u64 sector;
u64 len;
u64 ts;
char disk_name[DISK_NAME_LEN];
char name[TASK_COMM_LEN];
};
BPF_HASH(start, struct request *, struct start_req_t);
BPF_HASH(infobyreq, struct request *, struct val_t);
BPF_PERF_OUTPUT(events);
// cache PID and comm by-req
int trace_pid_start(struct pt_regs *ctx, struct request *req)
{
struct val_t val = {};
u64 ts;
if (bpf_get_current_comm(&val.name, sizeof(val.name)) == 0) {
val.pid = bpf_get_current_pid_tgid() >> 32;
if (##QUEUE##) {
val.ts = bpf_ktime_get_ns();
}
infobyreq.update(&req, &val);
}
return 0;
}
// time block I/O
int trace_req_start(struct pt_regs *ctx, struct request *req)
{
struct start_req_t start_req = {
.ts = bpf_ktime_get_ns(),
.data_len = req->__data_len
};
start.update(&req, &start_req);
return 0;
}
// output
int trace_req_completion(struct pt_regs *ctx, struct request *req)
{
struct start_req_t *startp;
struct val_t *valp;
struct data_t data = {};
u64 ts;
// fetch timestamp and calculate delta
startp = start.lookup(&req);
if (startp == 0) {
// missed tracing issue
return 0;
}
ts = bpf_ktime_get_ns();
data.delta = ts - startp->ts;
data.ts = ts / 1000;
data.qdelta = 0;
valp = infobyreq.lookup(&req);
data.len = startp->data_len;
if (valp == 0) {
data.name[0] = '?';
data.name[1] = 0;
} else {
if (##QUEUE##) {
data.qdelta = startp->ts - valp->ts;
}
data.pid = valp->pid;
data.sector = req->__sector;
bpf_probe_read_kernel(&data.name, sizeof(data.name), valp->name);
struct gendisk *rq_disk = req->rq_disk;
bpf_probe_read_kernel(&data.disk_name, sizeof(data.disk_name),
rq_disk->disk_name);
}
/*
* The following deals with a kernel version change (in mainline 4.7, although
* it may be backported to earlier kernels) with how block request write flags
* are tested. We handle both pre- and post-change versions here. Please avoid
* kernel version tests like this as much as possible: they inflate the code,
* test, and maintenance burden.
*/
#ifdef REQ_WRITE
data.rwflag = !!(req->cmd_flags & REQ_WRITE);
#elif defined(REQ_OP_SHIFT)
data.rwflag = !!((req->cmd_flags >> REQ_OP_SHIFT) == REQ_OP_WRITE);
#else
data.rwflag = !!((req->cmd_flags & REQ_OP_MASK) == REQ_OP_WRITE);
#endif
events.perf_submit(ctx, &data, sizeof(data));
start.delete(&req);
infobyreq.delete(&req);
return 0;
}
"""
if args.queue:
bpf_text = bpf_text.replace('##QUEUE##', '1')
else:
bpf_text = bpf_text.replace('##QUEUE##', '0')
if debug or args.ebpf:
print(bpf_text)
if args.ebpf:
exit()
# initialize BPF
b = BPF(text=bpf_text)
if BPF.get_kprobe_functions(b'__blk_account_io_start'):
b.attach_kprobe(event="__blk_account_io_start", fn_name="trace_pid_start")
else:
b.attach_kprobe(event="blk_account_io_start", fn_name="trace_pid_start")
if BPF.get_kprobe_functions(b'blk_start_request'):
b.attach_kprobe(event="blk_start_request", fn_name="trace_req_start")
b.attach_kprobe(event="blk_mq_start_request", fn_name="trace_req_start")
if BPF.get_kprobe_functions(b'__blk_account_io_done'):
b.attach_kprobe(event="__blk_account_io_done", fn_name="trace_req_completion")
else:
b.attach_kprobe(event="blk_account_io_done", fn_name="trace_req_completion")
# header
print("%-11s %-14s %-6s %-7s %-1s %-10s %-7s" % ("TIME(s)", "COMM", "PID",
"DISK", "T", "SECTOR", "BYTES"), end="")
if args.queue:
print("%7s " % ("QUE(ms)"), end="")
print("%7s" % "LAT(ms)")
rwflg = ""
start_ts = 0
prev_ts = 0
delta = 0
# process event
def print_event(cpu, data, size):
event = b["events"].event(data)
global start_ts
if start_ts == 0:
start_ts = event.ts
if event.rwflag == 1:
rwflg = "W"
else:
rwflg = "R"
delta = float(event.ts) - start_ts
print("%-11.6f %-14.14s %-6s %-7s %-1s %-10s %-7s" % (
delta / 1000000, event.name.decode('utf-8', 'replace'), event.pid,
event.disk_name.decode('utf-8', 'replace'), rwflg, event.sector,
event.len), end="")
if args.queue:
print("%7.2f " % (float(event.qdelta) / 1000000), end="")
print("%7.2f" % (float(event.delta) / 1000000))
# loop with callback to print_event
b["events"].open_perf_buffer(print_event, page_cnt=64)
while 1:
try:
b.perf_buffer_poll()
except KeyboardInterrupt:
exit()
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