linux-kernel - Re: Kaffeine problem with CFS

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Message-ID: <20070418161459.GA21351@elte.hu>
Date:	Wed, 18 Apr 2007 18:14:59 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	William Lee Irwin III <wli@...omorphy.com>
Cc:	"S.??a??lar Onur" <caglar@...dus.org.tr>,
	Christoph Pfister <christophpfister@...il.com>,
	linux-kernel@...r.kernel.org,
	Michael Lothian <mike@...eburn.co.uk>,
	Christophe Thommeret <hftom@...e.fr>,
	Jurgen Kofler <kaffeine@....net>,
	Ulrich Drepper <drepper@...hat.com>
Subject: Re: Kaffeine problem with CFS


* William Lee Irwin III <wli@...omorphy.com> wrote:

> At this point you might as well call the requeue operation something 
> having to do with yield. [...]

agreed - i've just done a requeue_task -> yield_task rename in my tree. 
(patch below)

> [...] I also suspect what goes on during the timer tick may eventually 
> become something different from requeueing the current task, and 
> furthermore class-dependent.

it already is, scheduler tick processing is done in class->task_tick().

	Ingo

---
 include/linux/sched.h |    2 +-
 kernel/sched.c        |    7 +------
 kernel/sched_fair.c   |    4 ++--
 kernel/sched_rt.c     |    2 +-
 4 files changed, 5 insertions(+), 10 deletions(-)

Index: linux/include/linux/sched.h
===================================================================
--- linux.orig/include/linux/sched.h
+++ linux/include/linux/sched.h
@@ -796,7 +796,7 @@ struct sched_class {
 
 	void (*enqueue_task) (struct rq *rq, struct task_struct *p);
 	void (*dequeue_task) (struct rq *rq, struct task_struct *p);
-	void (*requeue_task) (struct rq *rq, struct task_struct *p);
+	void (*yield_task) (struct rq *rq, struct task_struct *p);
 
 	void (*check_preempt_curr) (struct rq *rq, struct task_struct *p);
 
Index: linux/kernel/sched.c
===================================================================
--- linux.orig/kernel/sched.c
+++ linux/kernel/sched.c
@@ -560,11 +560,6 @@ static void dequeue_task(struct rq *rq, 
 	p->on_rq = 0;
 }
 
-static void requeue_task(struct rq *rq, struct task_struct *p)
-{
-	p->sched_class->requeue_task(rq, p);
-}
-
 /*
  * __normal_prio - return the priority that is based on the static prio
  */
@@ -3773,7 +3768,7 @@ asmlinkage long sys_sched_yield(void)
 	schedstat_inc(rq, yld_cnt);
 	if (rq->nr_running == 1)
 		schedstat_inc(rq, yld_act_empty);
-	requeue_task(rq, current);
+	current->sched_class->yield_task(rq, current);
 
 	/*
 	 * Since we are going to call schedule() anyway, there's
Index: linux/kernel/sched_fair.c
===================================================================
--- linux.orig/kernel/sched_fair.c
+++ linux/kernel/sched_fair.c
@@ -273,7 +273,7 @@ static void dequeue_task_fair(struct rq 
  * dequeue the task and move it to the rightmost position, which
  * causes the task to roundrobin to the end of the tree.
  */
-static void requeue_task_fair(struct rq *rq, struct task_struct *p)
+static void yield_task_fair(struct rq *rq, struct task_struct *p)
 {
 	dequeue_task_fair(rq, p);
 	p->on_rq = 0;
@@ -509,7 +509,7 @@ static void task_init_fair(struct rq *rq
 struct sched_class fair_sched_class __read_mostly = {
 	.enqueue_task		= enqueue_task_fair,
 	.dequeue_task		= dequeue_task_fair,
-	.requeue_task		= requeue_task_fair,
+	.yield_task		= yield_task_fair,
 
 	.check_preempt_curr	= check_preempt_curr_fair,
 
Index: linux/kernel/sched_rt.c
===================================================================
--- linux.orig/kernel/sched_rt.c
+++ linux/kernel/sched_rt.c
@@ -165,7 +165,7 @@ static void task_init_rt(struct rq *rq, 
 static struct sched_class rt_sched_class __read_mostly = {
 	.enqueue_task		= enqueue_task_rt,
 	.dequeue_task		= dequeue_task_rt,
-	.requeue_task		= requeue_task_rt,
+	.yield_task		= requeue_task_rt,
 
 	.check_preempt_curr	= check_preempt_curr_rt,
 
-
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