From: Michael Wang <wangyun@linux.vnet.ibm.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] sched: Accelerate "pick_next_entity" under special condition
Date: Mon, 16 Jan 2012 18:34:45 +0800 [thread overview]
Message-ID: <4F13FD45.4000804@linux.vnet.ibm.com> (raw)
In-Reply-To: <1326707503.2442.219.camel@twins>
Hi, peter
Thanks so much for your reply :)
On 01/16/2012 05:51 PM, Peter Zijlstra wrote:
> On Mon, 2012-01-16 at 17:37 +0800, Michael Wang wrote:
>> From: Michael Wang <wangyun@linux.vnet.ibm.com>
>>
>> We can avoid some useless operation in some special condition.
>
> This is a pretty empty statement.
>
>> For example:
>> If we have "cfs_rq->next" and it can be use, we just return it directly.
>
> What it doesn't state is what it actually does, if it affects the common
> case and performance numbers (or a good reason for the lack thereof).
>
Please help me to understand the logic, I think in the original code,
even if we have cfs_rq->next and wakeup_preempt_entity check passed, we
still need to do a lot of work (check cfs_rq->last for example) which
have no influence on result, will it be better if we skip them and just
do what really needed?
>> Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
>> ---
>> kernel/sched/fair.c | 28 +++++++++++++++++-----------
>> 1 files changed, 17 insertions(+), 11 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 84adb2d..9fc2c3c 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -1295,6 +1295,8 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
>> static int
>> wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
>>
>> +#define ENTITY_PREEMPT_ALLOWED(prev,next) (wakeup_preempt_entity(prev, next) < 1)
>
> This is just uglification imo, its shouting and it doesn't actually win
> you much space.
>
I see, sorry for the bad idea.
Best regards,
Michael Wang
next prev parent reply other threads:[~2012-01-16 10:35 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-16 9:37 [PATCH] sched: Accelerate "pick_next_entity" under special condition Michael Wang
2012-01-16 9:50 ` Michael Wang
2012-01-16 9:51 ` Peter Zijlstra
2012-01-16 10:34 ` Michael Wang [this message]
2012-01-17 2:36 ` [PATCH v2] " Michael Wang
2012-01-17 2:41 ` Michael Wang
2012-01-17 2:58 ` Xiaotian Feng
2012-01-17 3:04 ` Michael Wang
2012-01-25 15:55 ` Peter Zijlstra
2012-01-26 10:04 ` Ingo Molnar
2012-01-27 1:22 ` Michael Wang
2012-01-27 4:42 ` Cong Wang
2012-01-29 6:32 ` Michael Wang
2012-01-29 16:33 ` Ingo Molnar
2012-01-30 3:18 ` Michael Wang
2012-01-30 3:25 ` Cong Wang
2012-01-30 5:47 ` Michael Wang
2012-07-03 6:34 ` [PATCH] sched: remove useless code in yield_to Michael Wang
2012-07-12 5:45 ` Michael Wang
2012-07-12 14:07 ` Peter Zijlstra
2012-07-12 18:44 ` Mike Galbraith
2012-07-16 2:39 ` Michael Wang
2012-08-17 6:56 ` Michael Wang
2012-08-17 9:43 ` Peter Zijlstra
2012-08-10 3:05 ` Michael Wang
2012-08-10 3:10 ` Michael Wang
2012-08-10 5:52 ` Mike Galbraith
2012-09-04 18:50 ` [tip:sched/core] sched: Remove useless code in yield_to() tip-bot for Michael Wang
2012-01-27 0:56 ` [PATCH v2] sched: Accelerate "pick_next_entity" under special condition Michael Wang
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