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| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2010-05-18 11:12:48 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2010-05-18 18:35:49 +0200 |
| commit | 6d1acfd5c6bfd5231c13a8f2858d7f2afbaa1b62 (patch) | |
| tree | abcfa95947cafc94c978a255b814472fe67cad22 | |
| parent | fa5881514ef9c9bcb29319aad85cf2d8889d91f1 (diff) | |
| download | linux-6d1acfd5c6bfd5231c13a8f2858d7f2afbaa1b62.tar.bz2 | |
perf: Optimize perf_output_*() by avoiding local_xchg()
Since the x86 XCHG ins implies LOCK, avoid the use by
using a sequence count instead.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | include/linux/perf_event.h | 1 | ||||
| -rw-r--r-- | kernel/perf_event.c | 3 |
2 files changed, 3 insertions, 1 deletions
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index ce7667616fcb..fe50347dc645 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -804,6 +804,7 @@ struct perf_output_handle { struct perf_mmap_data *data; unsigned long head; unsigned long offset; + unsigned long wakeup; int nmi; int sample; }; diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 1f98c78c3343..7e3bcf1a29f0 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -2917,6 +2917,7 @@ static void perf_output_get_handle(struct perf_output_handle *handle) preempt_disable(); local_inc(&data->nest); + handle->wakeup = local_read(&data->wakeup); } static void perf_output_put_handle(struct perf_output_handle *handle) @@ -2950,7 +2951,7 @@ again: goto again; } - if (local_xchg(&data->wakeup, 0)) + if (handle->wakeup != local_read(&data->wakeup)) perf_output_wakeup(handle); preempt_enable(); |