linux-kernel - Re: [patch 1/2] sched: move periodic share updates to entity

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Date:	Mon, 10 Jan 2011 15:49:21 -0800
From:	Paul Turner <pjt@...gle.com>
To:	Mike Galbraith <efault@....de>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch 1/2] sched: move periodic share updates to entity_tick()

Back from the Holidays and catching up on email -- Peter, looks like
this fix still needs merging?

On Thu, Dec 16, 2010 at 6:26 AM, Mike Galbraith <efault@....de> wrote:
> On Thu, 2010-12-16 at 12:03 +0100, Peter Zijlstra wrote:
>> I made that:
>
> Box is ill, I'll test these as soon as it's all better.
>
>> ---
>> Subject: sched: Move periodic share updates to entity_tick()
>> From: Paul Turner <pjt@...gle.com>
>> Date: Wed, 15 Dec 2010 19:10:17 -0800
>>
>> Long running entities that do not block (dequeue) require periodic updates to
>> maintain accurate share values.  (Note: group entities with several threads are
>> quite likely to be non-blocking in many circumstances).
>>
>> By virtue of being long-running however, we will see entity ticks (otherwise
>> the required update occurs in dequeue/put and we are done).  Thus we can move
>> the detection (and associated work) for these updates into the periodic path.
>>
>> This restores the 'atomicity' of update_curr() with respect to accounting.
>>
>> Signed-off-by: Paul Turner <pjt@...gle.com>
>> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>> LKML-Reference: <20101216031038.067028969@...gle.com>
>> ---
>>  kernel/sched_fair.c |   21 +++++++++++++++++----
>>  1 file changed, 17 insertions(+), 4 deletions(-)
>>
>> Index: linux-2.6/kernel/sched_fair.c
>> ===================================================================
>> --- linux-2.6.orig/kernel/sched_fair.c
>> +++ linux-2.6/kernel/sched_fair.c
>> @@ -564,10 +564,6 @@ __update_curr(struct cfs_rq *cfs_rq, str
>>
>>  #if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
>>       cfs_rq->load_unacc_exec_time += delta_exec;
>> -     if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
>> -             update_cfs_load(cfs_rq, 0);
>> -             update_cfs_shares(cfs_rq, 0);
>> -     }
>>  #endif
>>  }
>>
>> @@ -809,6 +805,14 @@ static void update_cfs_shares(struct cfs
>>
>>       reweight_entity(cfs_rq_of(se), se, shares);
>>  }
>> +
>> +static void update_entity_shares_tick(struct cfs_rq *cfs_rq)
>> +{
>> +     if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
>> +             update_cfs_load(cfs_rq, 0);
>> +             update_cfs_shares(cfs_rq, 0);
>> +     }
>> +}
>>  #else /* CONFIG_FAIR_GROUP_SCHED */
>>  static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
>>  {
>> @@ -817,6 +821,10 @@ static void update_cfs_load(struct cfs_r
>>  static inline void update_cfs_shares(struct cfs_rq *cfs_rq, long weight_delta)
>>  {
>>  }
>> +
>> +static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
>> +{
>> +}
>>  #endif /* CONFIG_FAIR_GROUP_SCHED */
>>
>>  static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
>> @@ -1133,6 +1141,11 @@ entity_tick(struct cfs_rq *cfs_rq, struc
>>        */
>>       update_curr(cfs_rq);
>>
>> +     /*
>> +      * Update share accounting for long-running entities.
>> +      */
>> +     update_entity_shares_tick(cfs_rq);
>> +
>>  #ifdef CONFIG_SCHED_HRTICK
>>       /*
>>        * queued ticks are scheduled to match the slice, so don't bother
>>
>
>
>
--
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