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Subject[tip:perf/core] perf: Optimize some swcounter attr.sample_period==1 paths
Commit-ID:  0cff784ae41cc125368ae77f1c01328ae2fdc6b3
Gitweb: http://git.kernel.org/tip/0cff784ae41cc125368ae77f1c01328ae2fdc6b3
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Fri, 20 Nov 2009 22:19:44 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Sat, 21 Nov 2009 14:11:35 +0100

perf: Optimize some swcounter attr.sample_period==1 paths

Avoid the rather expensive perf_swevent_set_period() if we know
we have to sample every single event anyway.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20091120212508.299508332@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/perf_event.c | 17 +++++++++++------
1 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 1dfb6cc..8e55b44 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -3759,16 +3759,16 @@ again:
return nr;
}

-static void perf_swevent_overflow(struct perf_event *event,
+static void perf_swevent_overflow(struct perf_event *event, u64 overflow,
int nmi, struct perf_sample_data *data,
struct pt_regs *regs)
{
struct hw_perf_event *hwc = &event->hw;
int throttle = 0;
- u64 overflow;

data->period = event->hw.last_period;
- overflow = perf_swevent_set_period(event);
+ if (!overflow)
+ overflow = perf_swevent_set_period(event);

if (hwc->interrupts == MAX_INTERRUPTS)
return;
@@ -3801,14 +3801,19 @@ static void perf_swevent_add(struct perf_event *event, u64 nr,

atomic64_add(nr, &event->count);

+ if (!regs)
+ return;
+
if (!hwc->sample_period)
return;

- if (!regs)
+ if (nr == 1 && hwc->sample_period == 1 && !event->attr.freq)
+ return perf_swevent_overflow(event, 1, nmi, data, regs);
+
+ if (atomic64_add_negative(nr, &hwc->period_left))
return;

- if (!atomic64_add_negative(nr, &hwc->period_left))
- perf_swevent_overflow(event, nmi, data, regs);
+ perf_swevent_overflow(event, 0, nmi, data, regs);
}

static int perf_swevent_is_counting(struct perf_event *event)

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