From: Michael Wang <wangyun@linux.vnet.ibm.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Xiaotian Feng <xtfeng@gmail.com>, ingo Molnar <mingo@elte.hu>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] sched: Accelerate "pick_next_entity" under special condition
Date: Fri, 27 Jan 2012 08:56:24 +0800 [thread overview]
Message-ID: <4F21F638.2080306@linux.vnet.ibm.com> (raw)
In-Reply-To: <1327506934.2614.87.camel@laptop>
On 01/25/2012 11:55 PM, Peter Zijlstra wrote:
> On Tue, 2012-01-17 at 11:04 +0800, Michael Wang wrote:
>>
>>> Then what if condition 1 is true now?
>>
>> We can see in original code, even condition 1 is true, we
>> still will use value3 if condition3 is true, like this:
>>
>> original:
>>
>> condition1 condition3 result
>> true true value3
>> true false value1
>>
>> That means if condition3 is true, we don't care whether
>> condition1 is true or not because we will finally use value3.
>
> Right, so from the original 8 possible states we used to evaluate 3*8 =
> 24 conditionals. The new code will reduce this to 1*4 + 2*2 + 2*3 = 14.
>
> Now I guess the question is if it matters for the modal or average
> state.
>
Hi, Peter
I think how much help this patch can do on the performance depends on
how often the condition2 and 3 occur.
> I've applied the patch since it can't be worse, but I've no idea if it
> matters or not in practice.
It's hardly to say how useful this patch is, but it will do some help
under special condition.
Thanks for your review.
Regards,
Michael Wang
>
prev parent reply other threads:[~2012-01-27 0:56 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
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 ` Michael Wang [this message]
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