5.7 BCC工具之disksnoop.py解读

一，disksnoop.py简介

disksnoop工具用于追踪块设备的I/O操作的延迟，它会在每次I/O执行完成后打印一行摘要信息。我们根据这些摘要日志，来分析当前的I/O操作是否存在延迟，以判断I/O是否达到了瓶颈。

二，代码示例

#!/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
from bcc.utils import printbREQ_WRITE = 1		# from include/linux/blk_types.h# load BPF program
b = BPF(text="""
#include <uapi/linux/ptrace.h>
#include <linux/blk-mq.h>BPF_HASH(start, struct request *);void trace_start(struct pt_regs *ctx, struct request *req) {// stash start timestamp by request ptru64 ts = bpf_ktime_get_ns();start.update(&am