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Subject[tip:perf/core] perf/x86/intel: Remove division from the intel_pmu_drain_pebs_nhm() hot path
Commit-ID:  eb8417aa703eff5ff43d0275f19b0a8e591d818d
Gitweb: http://git.kernel.org/tip/eb8417aa703eff5ff43d0275f19b0a8e591d818d
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Mon, 16 Sep 2013 09:23:02 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 20 Sep 2013 06:53:44 +0200

perf/x86/intel: Remove division from the intel_pmu_drain_pebs_nhm() hot path

Only do the division in case we have to print the result out in a warning.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-43nl31erfbajwpfj254f6zji@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/cpu/perf_event_intel_ds.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index f364c13..655d591 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -944,7 +944,7 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
struct perf_event *event = NULL;
void *at, *top;
u64 status = 0;
- int bit, n;
+ int bit;

if (!x86_pmu.pebs_active)
return;
@@ -954,16 +954,16 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)

ds->pebs_index = ds->pebs_buffer_base;

- n = (top - at) / x86_pmu.pebs_record_size;
- if (n <= 0)
+ if (unlikely(at > top))
return;

/*
* Should not happen, we program the threshold at 1 and do not
* set a reset value.
*/
- WARN_ONCE(n > x86_pmu.max_pebs_events,
- "Unexpected number of pebs records %d\n", n);
+ WARN_ONCE(top - at > x86_pmu.max_pebs_events * x86_pmu.pebs_record_size,
+ "Unexpected number of pebs records %ld\n",
+ (top - at) / x86_pmu.pebs_record_size);

for (; at < top; at += x86_pmu.pebs_record_size) {
struct pebs_record_nhm *p = at;

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