tools/funclatency

#!/usr/bin/python
#
# funclatency	Time kernel funcitons and print latency as a histogram.
#		For Linux, uses BCC, eBPF.
#
# USAGE: funclatency [-h] [-p PID] [-i INTERVAL] [-T] [-u] [-m] [-r] pattern
#
# Run "funclatency -h" for full usage.
#
# The pattern is a string with optional '*' wildcards, similar to file globbing.
# If you'd prefer to use regular expressions, use the -r option. Matching
# multiple functions is of limited use, since the output has one histogram for
# everything. Future versions should split the output histogram by the function.
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 20-Sep-2015	Brendan Gregg	Created this.

from __future__ import print_function
from bcc import BPF
from time import sleep, strftime
import argparse
import signal

# arguments
examples = """examples:
    ./funclatency do_sys_open       # time the do_sys_open() kenel function
    ./funclatency -u vfs_read       # time vfs_read(), in microseconds
    ./funclatency -m do_nanosleep   # time do_nanosleep(), in milliseconds
    ./funclatency -mTi 5 vfs_read   # output every 5 seconds, with timestamps
    ./funclatency -p 181 vfs_read   # time process 181 only
    ./funclatency 'vfs_fstat*'      # time both vfs_fstat() and vfs_fstatat()
"""
parser = argparse.ArgumentParser(
	description="Time kernel funcitons and print latency as a histogram",
	formatter_class=argparse.RawDescriptionHelpFormatter,
	epilog=examples)
parser.add_argument("-p", "--pid",
	help="trace this PID only")
parser.add_argument("-i", "--interval", default=99999999,
	help="summary interval, seconds")
parser.add_argument("-T", "--timestamp", action="store_true",
	help="include timestamp on output")
parser.add_argument("-u", "--microseconds", action="store_true",
	help="microsecond histogram")
parser.add_argument("-m", "--milliseconds", action="store_true",
	help="millisecond histogram")
parser.add_argument("-r", "--regexp", action="store_true",
	help="use regular expressions. Default is \"*\" wildcards only.")
parser.add_argument("pattern",
	help="search expression for kernel functions")
args = parser.parse_args()
pattern = args.pattern
if not args.regexp:
	pattern = pattern.replace('*', '.*')
	pattern = '^' + pattern + '$'
debug = 0

# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/blkdev.h>

BPF_HASH(start, u32);
BPF_HISTOGRAM(dist);

int trace_func_entry(struct pt_regs *ctx)
{
	u32 pid = bpf_get_current_pid_tgid();
	u64 ts = bpf_ktime_get_ns();

	FILTER
	start.update(&pid, &ts);

	return 0;
}

int trace_func_return(struct pt_regs *ctx)
{
	u64 *tsp, delta;
	u32 pid = bpf_get_current_pid_tgid();

	// calculate delta time
	tsp = start.lookup(&pid);
	if (tsp == 0) {
		return 0; 	// missed start
	}
	start.delete(&pid);
	delta = bpf_ktime_get_ns() - *tsp;
	FACTOR

	// store as histogram
	dist.increment(bpf_log2l(delta));

	return 0;
}
"""
if args.pid:
	bpf_text = bpf_text.replace('FILTER',
	    'if (pid != %s) { return 0; }' % args.pid)
else:
	bpf_text = bpf_text.replace('FILTER', '')
if args.milliseconds:
	bpf_text = bpf_text.replace('FACTOR', 'delta /= 1000000;')
	label = "msecs"
elif args.microseconds:
	bpf_text = bpf_text.replace('FACTOR', 'delta /= 1000;')
	label = "usecs"
else:
	bpf_text = bpf_text.replace('FACTOR', '')
	label = "nsecs"
if debug:
	print(bpf_text)

# signal handler
def signal_ignore(signal, frame):
	print()

# load BPF program
b = BPF(text=bpf_text)
b.attach_kprobe(event_re=pattern, fn_name="trace_func_entry")
b.attach_kretprobe(event_re=pattern, fn_name="trace_func_return")
matched = b.num_open_kprobes()
if matched == 0:
	print("0 functions matched by \"%s\". Exiting." % args.pattern)
	exit()

# header
print("Tracing %d functions for \"%s\"... Hit Ctrl-C to end." %
    (matched / 2, args.pattern))

# output
exiting = 0 if args.interval else 1
dist = b.get_table("dist")
while (1):
	try:
		sleep(int(args.interval))
	except KeyboardInterrupt:
		exiting=1
		# as cleanup can take many seconds, trap Ctrl-C:
		signal.signal(signal.SIGINT, signal_ignore)

	print()
	if args.timestamp:
		print("%-8s\n" % strftime("%H:%M:%S"), end="")

	dist.print_log2_hist(label)
	dist.clear()

	if exiting:
		print("Detaching...")
		exit()