[PATCH 3/4] perf_counter: optimize disable of time based sw counters

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

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Currently we call hrtimer_cancel() unconditionally on disable of time based
software counters. Avoid when possible.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 kernel/perf_counter.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/kernel/perf_counter.c
@@ -2716,7 +2716,8 @@ static int cpu_clock_perf_counter_enable
 
 static void cpu_clock_perf_counter_disable(struct perf_counter *counter)
 {
-	hrtimer_cancel(&counter->hw.hrtimer);
+	if (counter->hw.irq_period)
+		hrtimer_cancel(&counter->hw.hrtimer);
 	cpu_clock_perf_counter_update(counter);
 }
 
@@ -2767,7 +2768,8 @@ static int task_clock_perf_counter_enabl
 
 static void task_clock_perf_counter_disable(struct perf_counter *counter)
 {
-	hrtimer_cancel(&counter->hw.hrtimer);
+	if (counter->hw.irq_period)
+		hrtimer_cancel(&counter->hw.hrtimer);
 	task_clock_perf_counter_update(counter, counter->ctx->time);
 
 }

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