[tip:sched/core] sched: Feature to disable APERF/MPERF cpu_power

tip-bot for Peter Zijlstra
2009-09-16T10:24:09Z

Commit-ID: 8e6598af3f35629c37249a610cf13e73f70db279
Gitweb: http://git.kernel.org/tip/8e6598af3f35629c37249a610cf13e73f70db279
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Thu, 3 Sep 2009 13:20:03 +0200
Committer: Ingo Molnar <mingo@elte.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@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.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)