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authorPeter Zijlstra <peterz@infradead.org>2019-05-17 14:52:34 +0300
committerIngo Molnar <mingo@kernel.org>2019-05-24 10:00:11 +0300
commit5322ea58a06da2e69c5ef36a9b4d4b9255edd423 (patch)
tree3d40eddd863065f3c365fb938880196c6645da3a /kernel/events/internal.h
parent4d839dd9e4356bbacf3eb0ab13a549b83b008c21 (diff)
downloadlinux-5322ea58a06da2e69c5ef36a9b4d4b9255edd423.tar.xz
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.h4
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;