bcc/misc/futex-contention.py

# futex contention
# (c) 2010, Arnaldo Carvalho de Melo <acme@redhat.com>
# Licensed under the terms of the GNU GPL License version 2
#
# Translation of:
#
# http://sourceware.org/systemtap/wiki/WSFutexContention
#
# to perf python scripting.
#
# Measures futex contention

import os, sys
sys.path.append(os.environ['PERF_EXEC_PATH'] + '/scripts/python/Perf-Trace-Util/lib/Perf/Trace')
from Util import *

process_names = {}
thread_thislock = {}
thread_blocktime = {}

lock_waits = {} # long-lived stats on (tid,lock) blockage elapsed time
process_names = {} # long-lived pid-to-execname mapping

def android_lock(callchain):
    for c in callchain:
        if 'sym' in c and 'name' in c['sym']:
            name = c['sym']['name']
        else:
            continue

        if 'art::Monitor::Lock' in name:
            return True
    return False

def syscalls__sys_enter_futex(event, ctxt, cpu, s, ns, tid, comm, callchain,
			      nr, uaddr, op, val, utime, uaddr2, val3):

	cmd = op & FUTEX_CMD_MASK
        if cmd != FUTEX_WAIT or android_lock(callchain) == False:
		return # we don't care about originators of WAKE events 
                       # or futex uses that aren't android locks.

	process_names[tid] = comm
	thread_thislock[tid] = uaddr
	thread_blocktime[tid] = nsecs(s, ns)

def syscalls__sys_exit_futex(event, ctxt, cpu, s, ns, tid, comm, callchain,
			     nr, ret):
	if thread_blocktime.has_key(tid):
		elapsed = nsecs(s, ns) - thread_blocktime[tid]
		add_stats(lock_waits, (tid, thread_thislock[tid]), elapsed)
		del thread_blocktime[tid]
		del thread_thislock[tid]

def trace_begin():
	print "Press control+C to stop and show the summary"

def trace_end():
	for (tid, lock) in lock_waits:
		min, max, avg, count = lock_waits[tid, lock]
		print "%s[%d] lock %x contended %d times, %d avg ns" % \
		      (process_names[tid], tid, lock, count, avg)