linux-kernel - Re: [PATCH RFC/TEST] sched: make sync affine wakeups work

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Message-ID: <536C3B69.1000208@redhat.com>
Date:	Thu, 08 May 2014 22:20:25 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Mike Galbraith <umgwanakikbuti@...il.com>,
	linux-kernel@...r.kernel.org, morten.rasmussen@....com,
	mingo@...nel.org, george.mccollister@...il.com,
	ktkhai@...allels.com
Subject: Re: [PATCH RFC/TEST] sched: make sync affine wakeups work

On 05/06/2014 04:39 PM, Peter Zijlstra wrote:
> On Tue, May 06, 2014 at 04:19:21PM -0400, Rik van Riel wrote:
>> On 05/06/2014 07:54 AM, Peter Zijlstra wrote:
>>> On Fri, May 02, 2014 at 11:19:47AM -0400, Rik van Riel wrote:
>>>> As an aside, it also looks like SD_BALANCE_WAKE is set on all domains
>                                      ^^^^^^^^^^^^^^^

> No BALANCE_WAKE there

Looks like SD_BALANCE_WAKE is not gotten from the sd flags at
all, but passed into select_task_rq by try_to_wake_up, as a
hard coded sd_flags argument.

static int
try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
{
...
        cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
...

static inline
int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int
wake_flags)
{
        cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
...

static int
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag,
int wake_flags)
{
...

        if (sd_flag & SD_BALANCE_WAKE) {
                if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
                        want_affine = 1;
                new_cpu = prev_cpu;
        }

Should we do that, if SD_WAKE_BALANCE is not set for any sched domain?

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