一，工具简介

vfsreadlat.py工具用于跟踪VFS读取延迟分布情况，示例的运行结果是一个函数延迟分布直方图。

二，代码示例

#!/usr/bin/python# USAGE: vfsreadlat.py [interval [count]]
#
# The default interval is 5 seconds. A Ctrl-C will print the partially
# gathered histogram then exit.
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 15-Aug-2015	Brendan Gregg	Created this.from __future__ import print_function
from bcc import BPF
from time import sleep
from sys import argvdef usage():print("USAGE: %s [interval [count]]" % argv[0])exit()# 参数
interval = 5
count = -1
if len(argv) > 1:try:interval = int(argv[1])if interval == 0:raiseif len(argv) > 2:count = int(argv[2])except:	# also catches -h, --helpusage()# 加载BPF程序
b = BPF(src_file = "vfsreadlat.c")
b.attach_kprobe(event="vfs_read