linux-kernel - Re: [PATCH v2 0/11] remove cpu

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Message-ID: <53048626.2000803@linaro.org>
Date:	Wed, 19 Feb 2014 18:23:34 +0800
From:	Alex Shi <alex.shi@...aro.org>
To:	Vincent Guittot <vincent.guittot@...aro.org>
CC:	Morten Rasmussen <morten.rasmussen@....com>,
	"mingo@...hat.com" <mingo@...hat.com>,
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Subject: Re: [PATCH v2 0/11] remove cpu_load in rq


>> Removing cpu_load completely certainly makes things simpler, my worry is
>> just how much was lost by doing it. I agree that cpu_load needs a
>> cleanup, but I can't convince myself that just removing it completely
>> and not having any longer term view of cpu load anymore is without any
>> negative side-effects.
> 
> Hi Alex,
> 
> Have you followed this thread about load_idx and the interest of using
> them to use different average period ?
> https://lkml.org/lkml/2014/1/6/499

Yes, I hoped to use blocked load before. But I still can not figure out
the correct usage of it.
Or maybe we need more quick decay for blocked load?
Or, maybe clean cpu_load is helpful to make room to reconsider this.
> 
> Vincent
> 
>>
>> {source, target}_load() are now instantaneous views of the cpu load,
>> which means that they may change very frequently. That could potentially
>> lead to more task migrations at all levels in the domain hierarchy as we
>> no longer have the more conservative cpu_load[] indexes that were used
>> at NUMA level.
>>
>> Maybe some of the NUMA experts have an opinion about this?
>>
>> In the discussions around V1 I think blocked load came up again as a
>> potential replacement for the current cpu_load array. There are some
>> issues that need to be solved around blocked_load first though.
>>
>> Morten


-- 
Thanks
    Alex
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