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| author | Peter Zijlstra <peterz@infradead.org> | 2019-05-17 13:52:34 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2019-05-24 09:00:11 +0200 |
| commit | 5322ea58a06da2e69c5ef36a9b4d4b9255edd423 (patch) | |
| tree | 3d40eddd863065f3c365fb938880196c6645da3a /kernel/events/internal.h | |
| parent | perf/ring-buffer: Always use {READ,WRITE}_ONCE() for rb->user_page data (diff) | |
| download | linux-5322ea58a06da2e69c5ef36a9b4d4b9255edd423.tar.xz linux-5322ea58a06da2e69c5ef36a9b4d4b9255edd423.zip | |
perf/ring-buffer: Use regular variables for nesting
While the IRQ/NMI will nest, the nest-count will be invariant over the
actual exception, since it will decrement equal to increment.
This means we can -- carefully -- use a regular variable since the
typical LOAD-STORE race doesn't exist (similar to preempt_count).
This optimizes the ring-buffer for all LOAD-STORE architectures, since
they need to use atomic ops to implement local_t.
Suggested-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: acme@kernel.org
Cc: mark.rutland@arm.com
Cc: namhyung@kernel.org
Cc: yabinc@google.com
Link: http://lkml.kernel.org/r/20190517115418.481392777@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events/internal.h')
| -rw-r--r-- | kernel/events/internal.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/events/internal.h b/kernel/events/internal.h index 79c47076700a..3aef4191798c 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -24,7 +24,7 @@ struct ring_buffer { atomic_t poll; /* POLL_ for wakeups */ local_t head; /* write position */ - local_t nest; /* nested writers */ + unsigned int nest; /* nested writers */ local_t events; /* event limit */ local_t wakeup; /* wakeup stamp */ local_t lost; /* nr records lost */ @@ -41,7 +41,7 @@ struct ring_buffer { /* AUX area */ long aux_head; - local_t aux_nest; + unsigned int aux_nest; long aux_wakeup; /* last aux_watermark boundary crossed by aux_head */ unsigned long aux_pgoff; int aux_nr_pages; |