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perf bench futex: Sanitize -q option in requeue 

When given the number of threads to requeue at once by user input,
there's always the risk of this value being larger than the total number
of threads.  This doesn't make any sense, and the kernel can easily deal
with such sort of situations, hence no big deal. We should however
prevent bogus output such as:

./perf bench --repeat 2 futex requeue -q 10
Run summary [PID 22210]: Requeuing 4 threads (from [private] 0x99ef3c to 0x99ef38), 10 at a time.

[Run 1]: Requeued 10 of 4 threads in 0.0040 ms
[Run 2]: Requeued 10 of 4 threads in 0.0030 ms
Requeued 10 of 4 threads in 0.0035 ms (+-14.29%)

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Davidlohr Bueso <dbueso@suse.de>
Link: http://lkml.kernel.org/r/1412008868-22328-2-git-send-email-dave@stgolabs.net
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Davidlohr Bueso 2014-09-29 09:41:08 -07:00 committed by Arnaldo Carvalho de Melo
parent 86c87e13f8
commit e19685ed24
1 changed files with 3 additions and 1 deletions
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4
tools/perf/bench/futex-requeue.c
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@ -172,6 +172,9 @@ int bench_futex_requeue(int argc, const char **argv,
gettimeofday(&end, NULL);
timersub(&end, &start, &runtime);
if (nrequeued > nthreads)
nrequeued = nthreads;
update_stats(&requeued_stats, nrequeued);
update_stats(&requeuetime_stats, runtime.tv_usec);
@ -190,7 +193,6 @@ int bench_futex_requeue(int argc, const char **argv,
if (ret)
err(EXIT_FAILURE, "pthread_join");
}
}
/* cleanup & report results */