linux-kernel - [tip:perfcounters/core] perf_counter: Optimize disable of time based sw counters

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Date:	Wed, 20 May 2009 17:19:09 GMT
From:	tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, acme@...hat.com, paulus@...ba.org,
	hpa@...or.com, mingo@...hat.com, jkacur@...hat.com,
	a.p.zijlstra@...llo.nl, mtosatti@...hat.com, tglx@...utronix.de,
	cjashfor@...ux.vnet.ibm.com, mingo@...e.hu
Subject: [tip:perfcounters/core] perf_counter: Optimize disable of time based sw counters

Commit-ID:  b986d7ec0f8b7ea3cc7366d80a137fbe839df227
Gitweb:     http://git.kernel.org/tip/b986d7ec0f8b7ea3cc7366d80a137fbe839df227
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Wed, 20 May 2009 12:21:21 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 20 May 2009 12:43:33 +0200

perf_counter: Optimize disable of time based sw counters

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

[ Impact: micro-optimize the code ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Corey Ashford <cjashfor@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: John Kacur <jkacur@...hat.com>
LKML-Reference: <20090520102553.388185031@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 kernel/perf_counter.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index db02eb1..473ed2c 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -2716,7 +2716,8 @@ static int cpu_clock_perf_counter_enable(struct perf_counter *counter)
 
 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_enable(struct perf_counter *counter)
 
 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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