From 384c5fe974abe35ab11dce4446dc5eed86585a3b Mon Sep 17 00:00:00 2001 From: "Frank Ch. Eigler" Date: Thu, 7 Aug 2008 16:47:18 -0400 Subject: samples: separate into subdirectories by subsystem --- testsuite/systemtap.examples/process/futexes.stp | 36 ++++++++++++++++++++++++ 1 file changed, 36 insertions(+) create mode 100755 testsuite/systemtap.examples/process/futexes.stp (limited to 'testsuite/systemtap.examples/process/futexes.stp') diff --git a/testsuite/systemtap.examples/process/futexes.stp b/testsuite/systemtap.examples/process/futexes.stp new file mode 100755 index 00000000..16c62937 --- /dev/null +++ b/testsuite/systemtap.examples/process/futexes.stp @@ -0,0 +1,36 @@ +#! /usr/bin/env stap + +# This script tries to identify contended user-space locks by hooking +# into the futex system call. + +global thread_thislock # short +global thread_blocktime # +global FUTEX_WAIT = 0 /*, FUTEX_WAKE = 1 */ + +global lock_waits # long-lived stats on (tid,lock) blockage elapsed time +global process_names # long-lived pid-to-execname mapping + +probe syscall.futex { + if (op != FUTEX_WAIT) next # we don't care about originators of WAKE events + t = tid () + process_names[pid()] = execname() + thread_thislock[t] = $uaddr + thread_blocktime[t] = gettimeofday_us() +} + +probe syscall.futex.return { + t = tid() + ts = thread_blocktime[t] + if (ts) { + elapsed = gettimeofday_us() - ts + lock_waits[pid(), thread_thislock[t]] <<< elapsed + delete thread_blocktime[t] + delete thread_thislock[t] + } +} + +probe end { + foreach ([pid+, lock] in lock_waits) + printf ("%s[%d] lock %p contended %d times, %d avg us\n", + process_names[pid], pid, lock, @count(lock_waits[pid,lock]), @avg(lock_waits[pid,lock])) +} -- cgit