linux-kernel - [tip:sched/core] sched: Feature to disable APERF/MPERF cpu

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Date:	Wed, 16 Sep 2009 10:23:36 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, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:sched/core] sched: Feature to disable APERF/MPERF cpu_power

Commit-ID:  8e6598af3f35629c37249a610cf13e73f70db279
Gitweb:     http://git.kernel.org/tip/8e6598af3f35629c37249a610cf13e73f70db279
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Thu, 3 Sep 2009 13:20:03 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 15 Sep 2009 16:51:28 +0200

sched: Feature to disable APERF/MPERF cpu_power

I suspect a feed-back loop between cpuidle and the aperf/mperf
cpu_power bits, where when we have idle C-states lower the ratio,
which leads to lower cpu_power and then less load, which generates
more idle time, etc..

Put in a knob to disable it.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 kernel/sched.c          |   12 ++++++++++--
 kernel/sched_features.h |    5 +++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index c210321..e8e603b 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3602,11 +3602,19 @@ static void update_cpu_power(struct sched_domain *sd, int cpu)
 	unsigned long power = SCHED_LOAD_SCALE;
 	struct sched_group *sdg = sd->groups;
 
-	power *= arch_scale_freq_power(sd, cpu);
+	if (sched_feat(ARCH_POWER))
+		power *= arch_scale_freq_power(sd, cpu);
+	else
+		power *= default_scale_freq_power(sd, cpu);
+
 	power >>= SCHED_LOAD_SHIFT;
 
 	if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
-		power *= arch_scale_smt_power(sd, cpu);
+		if (sched_feat(ARCH_POWER))
+			power *= arch_scale_smt_power(sd, cpu);
+		else
+			power *= default_scale_smt_power(sd, cpu);
+
 		power >>= SCHED_LOAD_SHIFT;
 	}
 
diff --git a/kernel/sched_features.h b/kernel/sched_features.h
index e98c2e8..294e10e 100644
--- a/kernel/sched_features.h
+++ b/kernel/sched_features.h
@@ -82,6 +82,11 @@ SCHED_FEAT(LAST_BUDDY, 1)
  */
 SCHED_FEAT(CACHE_HOT_BUDDY, 1)
 
+/*
+ * Use arch dependent cpu power functions
+ */
+SCHED_FEAT(ARCH_POWER, 0)
+
 SCHED_FEAT(HRTICK, 0)
 SCHED_FEAT(DOUBLE_TICK, 0)
 SCHED_FEAT(LB_BIAS, 1)
--
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