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| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2016-10-16 21:08:02 +0200 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2016-10-24 11:07:45 -0300 |
| commit | 34b753007d646482a4125a7095e1d1986d395f95 (patch) | |
| tree | 266d4c9ebb091a9bcc6f7b2268ef13abf0125ed3 | |
| parent | 899735066a8d945b7ae56a34847298fd0dd2104b (diff) | |
perf bench futex: Cache align the worker struct
It popped up in perf testing that the worker consumes some amount of
CPU. It boils down to the increment of `ops` which causes cache line
bouncing between the individual threads.
This patch aligns the struct by 256 bytes to ensure that not a cache
line is shared among CPUs. 128 byte is the x86 worst case and grep says
that L1_CACHE_SHIFT is set to 8 on s390.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20161016190803.3392-1-bigeasy@linutronix.de
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
| -rw-r--r-- | tools/perf/bench/futex-hash.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/tools/perf/bench/futex-hash.c b/tools/perf/bench/futex-hash.c index 8024cd5febd2..d9e5e80bb4d0 100644 --- a/tools/perf/bench/futex-hash.c +++ b/tools/perf/bench/futex-hash.c @@ -39,12 +39,15 @@ static unsigned int threads_starting; static struct stats throughput_stats; static pthread_cond_t thread_parent, thread_worker; +#define SMP_CACHE_BYTES 256 +#define __cacheline_aligned __attribute__ ((aligned (SMP_CACHE_BYTES))) + struct worker { int tid; u_int32_t *futex; pthread_t thread; unsigned long ops; -}; +} __cacheline_aligned; static const struct option options[] = { OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"), |