From: Michael wang <wangyun@linux.vnet.ibm.com>
To: Mike Galbraith <bitbucket@online.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>, Paul Turner <pjt@google.com>,
Rik van Riel <riel@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH] sched: Avoid select_idle_sibling() for wake_affine(.sync=true)
Date: Thu, 26 Sep 2013 15:26:45 +0800 [thread overview]
Message-ID: <5243E1B5.4080409@linux.vnet.ibm.com> (raw)
In-Reply-To: <1380179397.7525.45.camel@marge.simpson.net>
On 09/26/2013 03:09 PM, Mike Galbraith wrote:
[snip]
>>
>> Ok, a double-edged sword I see :)
>>
>> May be we can wave it carefully here, give the discount to a bigger
>> scope not the sync cpu, for example:
>>
>> sg1 sg2
>> cpu0 cpu1 cpu2 cpu3 cpu4 cpu5 cpu6 cpu7
>> waker idle idle idle idle idle idle idle
>>
>> If it's sync wakeup on cpu0 (only waker), and the sg is wide enough,
>> which means one cpu is not so influencial, then suppose cpu0 to be idle
>> could be more safe, also prefer sg1 than sg2 is more likely to be right.
>>
>> And we can still choose idle-cpu at final step, like cpu1 in this case,
>> to avoid the risk that waker don't get off as it said.
>>
>> The key point is to reduce the influence of sync, trust a little but not
>> totally ;-)
>
> What we need is a dirt cheap way to fairly accurately predict overlap
> potential (todo: write omniscience().. patent, buy planet).
Agree, solutions for such cases are usually incredible ;-)
Regards,
Michael Wang
>
> -Mike
>
> --
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next prev parent reply other threads:[~2013-09-26 7:27 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-25 7:53 [RFC][PATCH] sched: Avoid select_idle_sibling() for wake_affine(.sync=true) Peter Zijlstra
2013-09-25 8:56 ` Mike Galbraith
2013-09-26 2:50 ` Michael wang
2013-09-26 3:41 ` Mike Galbraith
2013-09-26 5:12 ` Michael wang
2013-09-26 5:34 ` Mike Galbraith
2013-09-26 6:15 ` Mike Galbraith
2013-09-26 6:32 ` Michael wang
2013-09-26 7:09 ` Mike Galbraith
2013-09-26 7:26 ` Michael wang [this message]
2013-09-26 9:58 ` Peter Zijlstra
2013-09-26 10:05 ` Peter Zijlstra
2013-09-26 10:55 ` Paul Turner
2013-09-26 11:16 ` Peter Zijlstra
2013-09-26 11:39 ` Paul Turner
2013-09-26 14:35 ` Peter Zijlstra
2013-09-26 15:43 ` Peter Zijlstra
2013-09-26 13:46 ` Mike Galbraith
2013-09-26 15:09 ` Michael wang
2013-09-26 15:44 ` Peter Zijlstra
2013-09-27 1:19 ` Michael wang
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