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Copy pathbiosnoop.py
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executable file
·188 lines (158 loc) · 4.75 KB
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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 ctypes as ct
import re
# load BPF program
b = BPF(text="""
#include <uapi/linux/ptrace.h>
#include <linux/blkdev.h>
struct val_t {
u32 pid;
char name[TASK_COMM_LEN];
};
struct data_t {
u32 pid;
u64 rwflag;
u64 delta;
u64 sector;
u64 len;
u64 ts;
char disk_name[DISK_NAME_LEN];
char name[TASK_COMM_LEN];
};
BPF_HASH(start, struct request *);
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 = {};
if (bpf_get_current_comm(&val.name, sizeof(val.name)) == 0) {
val.pid = bpf_get_current_pid_tgid();
infobyreq.update(&req, &val);
}
return 0;
}
// time block I/O
int trace_req_start(struct pt_regs *ctx, struct request *req)
{
u64 ts;
ts = bpf_ktime_get_ns();
start.update(&req, &ts);
return 0;
}
// output
int trace_req_completion(struct pt_regs *ctx, struct request *req)
{
u64 *tsp, delta;
u32 *pidp = 0;
struct val_t *valp;
struct data_t data = {};
u64 ts;
// fetch timestamp and calculate delta
tsp = start.lookup(&req);
if (tsp == 0) {
// missed tracing issue
return 0;
}
ts = bpf_ktime_get_ns();
data.delta = ts - *tsp;
data.ts = ts / 1000;
valp = infobyreq.lookup(&req);
if (valp == 0) {
data.len = req->__data_len;
strcpy(data.name, "?");
} else {
data.pid = valp->pid;
data.len = req->__data_len;
data.sector = req->__sector;
bpf_probe_read(&data.name, sizeof(data.name), valp->name);
bpf_probe_read(&data.disk_name, sizeof(data.disk_name),
req->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;
}
""", debug=0)
b.attach_kprobe(event="blk_account_io_start", fn_name="trace_pid_start")
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")
b.attach_kprobe(event="blk_account_io_completion",
fn_name="trace_req_completion")
TASK_COMM_LEN = 16 # linux/sched.h
DISK_NAME_LEN = 32 # linux/genhd.h
class Data(ct.Structure):
_fields_ = [
("pid", ct.c_ulonglong),
("rwflag", ct.c_ulonglong),
("delta", ct.c_ulonglong),
("sector", ct.c_ulonglong),
("len", ct.c_ulonglong),
("ts", ct.c_ulonglong),
("disk_name", ct.c_char * DISK_NAME_LEN),
("name", ct.c_char * TASK_COMM_LEN)
]
# header
print("%-14s %-14s %-6s %-7s %-2s %-9s %-7s %7s" % ("TIME(s)", "COMM", "PID",
"DISK", "T", "SECTOR", "BYTES", "LAT(ms)"))
rwflg = ""
start_ts = 0
prev_ts = 0
delta = 0
# process event
def print_event(cpu, data, size):
event = ct.cast(data, ct.POINTER(Data)).contents
val = -1
global start_ts
global prev_ts
global delta
if event.rwflag == 1:
rwflg = "W"
if event.rwflag == 0:
rwflg = "R"
if not re.match(b'\?', event.name):
val = event.sector
if start_ts == 0:
prev_ts = start_ts
if start_ts == 1:
delta = float(delta) + (event.ts - prev_ts)
print("%-14.9f %-14.14s %-6s %-7s %-2s %-9s %-7s %7.2f" % (
delta / 1000000, event.name.decode(), event.pid,
event.disk_name.decode(), rwflg, val,
event.len, float(event.delta) / 1000000))
prev_ts = event.ts
start_ts = 1
# loop with callback to print_event
b["events"].open_perf_buffer(print_event, page_cnt=64)
while 1:
b.kprobe_poll()