perf bench: Add futex-requeue microbenchmark

Block a bunch of threads on a futex and requeue them on another, N at a
time.

This program is particularly useful to measure the latency of nthread
requeues without waking up any tasks -- thus mimicking a regular
futex_wait.

An example run:

  $ perf bench futex requeue -r 100 -t 64
  Run summary [PID 151011]: Requeuing 64 threads (from 0x7d15c4 to 0x7d15c8), 1 at a time.

  [Run 1]: Requeued 64 of 64 threads in 0.0400 ms
  [Run 2]: Requeued 64 of 64 threads in 0.0390 ms
  [Run 3]: Requeued 64 of 64 threads in 0.0400 ms
  ...
  [Run 100]: Requeued 64 of 64 threads in 0.0390 ms
  Requeued 64 of 64 threads in 0.0399 ms (+-0.37%)

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <Waiman.Long@hp.com>
Link: http://lkml.kernel.org/r/1387081917-9102-4-git-send-email-davidlohr@hp.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h
index 6ac4509..71f2844 100644
--- a/tools/perf/bench/futex.h
+++ b/tools/perf/bench/futex.h
@@ -55,4 +55,17 @@ futex_wake(u_int32_t *uaddr, int nr_wake, int opflags)
 	return futex(uaddr, FUTEX_WAKE, nr_wake, NULL, NULL, 0, opflags);
 }
 
+/**
+* futex_cmp_requeue() - requeue tasks from uaddr to uaddr2
+* @nr_wake:        wake up to this many tasks
+* @nr_requeue:        requeue up to this many tasks
+*/
+static inline int
+futex_cmp_requeue(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2, int nr_wake,
+		 int nr_requeue, int opflags)
+{
+	return futex(uaddr, FUTEX_CMP_REQUEUE, nr_wake, nr_requeue, uaddr2,
+		 val, opflags);
+}
+
 #endif /* _FUTEX_H */