linux-kernel - Re: [PATCH V3 1/7] sched: Create sched_select_cpu() to give preferred CPU for power saving

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Date:	Tue, 19 Mar 2013 10:45:07 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	pjt@...gle.com, paul.mckenney@...aro.org, tglx@...utronix.de,
	tj@...nel.org, suresh.b.siddha@...el.com, venki@...gle.com,
	mingo@...hat.com, peterz@...radead.org, rostedt@...dmis.org,
	linaro-kernel@...ts.linaro.org, robin.randhawa@....com,
	Steve.Bannister@....com, Liviu.Dudau@....com,
	charles.garcia-tobin@....com, Arvind.Chauhan@....com,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 1/7] sched: Create sched_select_cpu() to give preferred
 CPU for power saving

On 18 March 2013 21:27, Frederic Weisbecker <fweisbec@...il.com> wrote:
> 2013/3/18 Viresh Kumar <viresh.kumar@...aro.org>:
>>> It would be nice to have some more precise naming. sched_select_busy_cpu() ?
>>
>> You are correct that name can be improved but busy may give it a different
>> meaning. Maybe sched_select_non_idle_cpu()?
>
> That works too yeah.

Here is the fixup that i applied (it fixes another stupid mistake in sched.h).
I have pushed this series here again:

http://git.linaro.org/gitweb?p=people/vireshk/linux.git;a=shortlog;h=refs/heads/sched-wq-migration-v3

commit e769ff0d78fd2fb504ae056a44b70bba7c259126
Author: Viresh Kumar <viresh.kumar@...aro.org>
Date:   Fri Sep 14 15:13:05 2012 +0530

    fixup! sched: Create sched_select_cpu() to give preferred CPU for
power saving

    Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 include/linux/sched.h | 19 ++++++++++---------
 kernel/sched/core.c   |  2 +-
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 216fa0d..db6655a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -231,11 +231,18 @@ extern void init_idle_bootup_task(struct
task_struct *idle);
 extern int runqueue_is_locked(int cpu);

 #ifdef CONFIG_SMP
-extern int sched_select_cpu(unsigned int sd_flags);
+extern int sched_select_non_idle_cpu(unsigned int sd_flags);
+#else
+static inline int sched_select_non_idle_cpu(unsigned int sd_flags)
+{
+       return smp_processor_id();
+}
+#endif

-#ifdef CONFIG_NO_HZ
+#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ)
 extern void nohz_balance_enter_idle(int cpu);
 extern void set_cpu_sd_state_idle(void);
+
 /*
  * In the semi idle case, use the nearest busy cpu for migrating timers
  * from an idle cpu.  This is good for power-savings.
@@ -244,17 +251,11 @@ extern void set_cpu_sd_state_idle(void);
  * selecting an idle cpu will add more delays to the timers than intended
  * (as that cpu's timer base may not be uptodate wrt jiffies etc).
  */
-#define get_nohz_timer_target() sched_select_cpu(0)
+#define get_nohz_timer_target() sched_select_non_idle_cpu(0)
 #else
 static inline void nohz_balance_enter_idle(int cpu) { }
 static inline void set_cpu_sd_state_idle(void) { }
-
-static inline int sched_select_cpu(unsigned int sd_flags)
-{
-       return raw_smp_processor_id();
-}
 #endif
-#endif /* CONFIG_SMP */

 /*
  * Only dump TASK_* tasks. (0 for all tasks)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ccd76d7..0265a5e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -627,7 +627,7 @@ void sched_avg_update(struct rq *rq)
  * returned back. If it is idle, then we must look for another CPU which have
  * all the flags passed as argument as set.
  */
-int sched_select_cpu(unsigned int sd_flags)
+int sched_select_non_idle_cpu(unsigned int sd_flags)
 {
        struct sched_domain *sd;
        int cpu = smp_processor_id();
--
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