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authorDavidlohr Bueso <dave@stgolabs.net>2015-04-24 10:00:48 -0700
committerArnaldo Carvalho de Melo <acme@redhat.com>2015-04-27 13:57:49 -0300
commit052b0f6eaf8b1f02669884a177bc3ce463133a42 (patch)
tree5384301c97a338573a97a7612105410d1c3e0dab /tools/perf/bench
parentd13855ef18e1852b2c4dc86ddf5759c5b34628cb (diff)
downloadlinux-052b0f6eaf8b1f02669884a177bc3ce463133a42.tar.gz
perf bench futex: Fix hung wakeup tasks after requeueing
The futex-requeue benchmark can hang because of missing wakeups once the benchmark is done, ie: [Run 1]: Requeued 1024 of 1024 threads in 0.3290 ms perf: couldn't wakeup all tasks (135/1024) This bug, while perhaps suggesting missing wakeups in kernel futex code, is merely a consequence of the crappy FUTEX_CMP_REQUEUE man page, incorrectly mentioning that the number of requeued tasks is in fact returned, not the wakeups. This patch acknowledges this and updates the corresponding futex_wake code around it. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Cc: Mel Gorman <mgorman@suse.de> Link: http://lkml.kernel.org/r/1429894848.10273.44.camel@stgolabs.net Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/bench')
-rw-r--r--tools/perf/bench/futex-requeue.c15
1 files changed, 8 insertions, 7 deletions
diff --git a/tools/perf/bench/futex-requeue.c b/tools/perf/bench/futex-requeue.c
index bedff6b5b3cf..ad0d9b5342fb 100644
--- a/tools/perf/bench/futex-requeue.c
+++ b/tools/perf/bench/futex-requeue.c
@@ -132,6 +132,9 @@ int bench_futex_requeue(int argc, const char **argv,
if (!fshared)
futex_flag = FUTEX_PRIVATE_FLAG;
+ if (nrequeue > nthreads)
+ nrequeue = nthreads;
+
printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %p), "
"%d at a time.\n\n", getpid(), nthreads,
fshared ? "shared":"private", &futex1, &futex2, nrequeue);
@@ -161,20 +164,18 @@ int bench_futex_requeue(int argc, const char **argv,
/* Ok, all threads are patiently blocked, start requeueing */
gettimeofday(&start, NULL);
- for (nrequeued = 0; nrequeued < nthreads; nrequeued += nrequeue) {
+ while (nrequeued < nthreads) {
/*
* Do not wakeup any tasks blocked on futex1, allowing
* us to really measure futex_wait functionality.
*/
- futex_cmp_requeue(&futex1, 0, &futex2, 0,
- nrequeue, futex_flag);
+ nrequeued += futex_cmp_requeue(&futex1, 0, &futex2, 0,
+ nrequeue, futex_flag);
}
+
gettimeofday(&end, NULL);
timersub(&end, &start, &runtime);
- if (nrequeued > nthreads)
- nrequeued = nthreads;
-
update_stats(&requeued_stats, nrequeued);
update_stats(&requeuetime_stats, runtime.tv_usec);
@@ -184,7 +185,7 @@ int bench_futex_requeue(int argc, const char **argv,
}
/* everybody should be blocked on futex2, wake'em up */
- nrequeued = futex_wake(&futex2, nthreads, futex_flag);
+ nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
if (nthreads != nrequeued)
warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads);