#!/usr/bin/python

#

# vfsreadlat.py VFS read latency distribution.

# For Linux, uses BCC, eBPF. See .c file.

#

# Written as a basic example of a function latency distribution histogram.

#

# 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 ctypes import c_ushort, c_int, c_ulonglong

from time import sleep

from sys import argv

def usage():

print("USAGE: %s [interval [count]]" % argv[0])

exit()

# arguments

interval = 5

count = -1

if len(argv) > 1:

try:

interval = int(argv[1])

if interval == 0:

raise

if len(argv) > 2:

count = int(argv[2])

except: # also catches -h, --help

usage()

# load BPF program

b = BPF(src_file = "vfsreadlat.c")

b.attach_kprobe(event="vfs_read", fn_name="do_entry")

b.attach_kretprobe(event="vfs_read", fn_name="do_return")

# header

print("Tracing... Hit Ctrl-C to end.")

# output

loop = 0

do_exit = 0

while (1):

if count > 0:

loop += 1

if loop > count:

exit()

try:

sleep(interval)

except KeyboardInterrupt:

pass; do_exit = 1

print()

b["dist"].print_log2_hist("usecs")

b["dist"].clear()

if do_exit:

exit()