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# 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
waker_wakee = {} # maps the futex waker to wakee
max_waits = {} # Details about a maximum contention like owner, owner chain
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 print_callchain(callchain):
for c in callchain:
if 'sym' in c and 'name' in c['sym']:
name = c['sym']['name']
else:
continue
print(" %s" % (name))
def sched__sched_waking(event_name, context, common_cpu,
common_secs, common_nsecs, common_pid, common_comm,
common_callchain, comm, pid, prio, success,
target_cpu):
waker_wakee[pid] = [common_pid, common_callchain]
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):
waker_pid = -1
waker_chain = "[no call chain]"
if thread_blocktime.has_key(tid):
# Gather stats about the contention (sum, min, max)
elapsed = nsecs(s, ns) - thread_blocktime[tid]
add_stats(lock_waits, (tid, thread_thislock[tid]), elapsed)
# Track details about the maximum contention seen
# including owner and its callchain
if (tid, thread_thislock[tid]) in max_waits:
prev_wait = max_waits[(tid, thread_thislock[tid])][0]
else:
prev_wait = 0
if elapsed > prev_wait:
if tid in waker_wakee:
waker_pid = waker_wakee[tid][0]
waker_chain = waker_wakee[tid][1]
max_waits[(tid, thread_thislock[tid])] = [elapsed, waker_pid, waker_chain, callchain]
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:
print("\n==============================================================\n")
min, max, avg, count = lock_waits[tid, lock]
print "%s[%d] lock %x contended %d times, %d avg ns, %d max ns" % \
(process_names[tid], tid, lock, count, avg, max)
print ""
if not (tid, lock) in max_waits:
print"Max contention info not available"
continue
print "Callstack of suffering task:"
print_callchain(max_waits[tid, lock][3])
print ""
waker_pid = max_waits[tid, lock][1]
waker_name = process_names[waker_pid] if waker_pid in process_names else "nameless-owner"
print "Owner %s caused this contention of %d ns. Owner's Call stack below:" % (waker_name, max_waits[tid, lock][0])
print_callchain(max_waits[tid, lock][2])
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