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bcc/disksnoop.py at 0c8c179fc1283600887efa46fe428022efc4151b · iovisor/bcc

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bcc/examples/tracing/disksnoop.py / Jump to

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#!/usr/bin/python
#
# disksnoop.py Trace block device I/O: basic version of iosnoop.
# For Linux, uses BCC, eBPF. Embedded C.
#
# Written as a basic example of tracing latency.
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 11-Aug-2015 Brendan Gregg Created this.
from __future__ import print_function
from bcc import BPF
REQ_WRITE = 1 # from include/linux/blk_types.h
# load BPF program
b = BPF(text="""
#include <uapi/linux/ptrace.h>
#include <linux/blkdev.h>
BPF_HASH(start, struct request *);
void trace_start(struct pt_regs *ctx, struct request *req) {
// stash start timestamp by request ptr
u64 ts = bpf_ktime_get_ns();
start.update(&req, &ts);
}
void trace_completion(struct pt_regs *ctx, struct request *req) {
u64 *tsp, delta;
tsp = start.lookup(&req);
if (tsp != 0) {
delta = bpf_ktime_get_ns() - *tsp;
bpf_trace_printk("%d %x %d\\n", req->__data_len,
req->cmd_flags, delta / 1000);
start.delete(&req);
}
}
""")
b.attach_kprobe(event="blk_start_request", fn_name="trace_start")
b.attach_kprobe(event="blk_mq_start_request", fn_name="trace_start")
b.attach_kprobe(event="blk_account_io_completion", fn_name="trace_completion")
# header
print("%-18s %-2s %-7s %8s" % ("TIME(s)", "T", "BYTES", "LAT(ms)"))
# format output
while 1:
(task, pid, cpu, flags, ts, msg) = b.trace_fields()
(bytes_s, bflags_s, us_s) = msg.split()
if int(bflags_s, 16) & REQ_WRITE:
type_s = "W"
elif bytes_s == "0": # see blk_fill_rwbs() for logic
type_s = "M"
else:
type_s = "R"
ms = float(int(us_s, 10)) / 1000
print("%-18.9f %-2s %-7s %8.2f" % (ts, type_s, bytes_s, ms))
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