linux-kernel - Re: [PATCH 1/2 v2.0]sched: Removing unused fields from /proc/schedstat

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Message-ID: <4D4FBC79.5070602@linux.vnet.ibm.com>
Date:	Mon, 07 Feb 2011 15:03:45 +0530
From:	Ciju Rajan K <ciju@...ux.vnet.ibm.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Satoru Takeuchi <takeuchi_satoru@...fujitsu.com>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Ciju Rajan K <ciju@...ux.vnet.ibm.com>
Subject: Re: [PATCH 1/2 v2.0]sched: Removing unused fields from /proc/schedstat

Hi Peter,

Could you please consider this patch set for inclusion?

-Ciju

On 02/03/2011 02:49 PM, Satoru Takeuchi wrote:
> Hi Ciju,
> 
> (2011/02/02 17:54), Ciju Rajan K wrote:
>> Hi Satoru,
>>
>>
>>>> I think we can remove rq->sched_switch and rq->sched_switch
>>>> without no problem because they are meaningless. The former
>>>> is for old O(1) scheduler and means the number of runqueue
>>>> switching among active/expired queue. The latter is for
>>>> SD_WAKE_BALANCE flag and its logic is already gone.
>>>>
>>>> However sbe_* are for SD_BALANCE_EXEC flag and sbf_* are for
>>>> SD_BALANCE_FORK flag. Since both logic for them are still alive,
>>>> the absence of these accounting is regression in my perspective.
>>>> In addition, these fields would be useful for analyzing load
>>>> balance behavior.
>>>>
>>
>> The sbe_*& sbf_* counters were added by the commit
>> 68767a0ae428801649d510d9a65bb71feed44dd1 But it was subsequently
>> removed by the commit 476d139c218e44e045e4bc6d4cc02b010b343939
> 
> OK, I understood. It's OK if user tools referring /proc/schedstat
> are released sync with this change.
> 
> I confirmed the following:
> 
> - This patch removes some unused schedstat fields and related
> data.
> - The kernel applying this patch works fine on my i386 box.
> 
> Tested-by: Satoru Takeuchi <takeuchi_satoru@...fujitsu.com>
> 
> Thanks,
> Satoru
> 
>>
>> [ciju@...u kernel]$ git describe 68767a0ae428801649d510d9a65bb71feed44dd1 --contains
>> v2.6.13-rc1~68^2~148
>> [ciju@...u kernel]$ git describe 476d139c218e44e045e4bc6d4cc02b010b343939 --contains
>> v2.6.13-rc1~68^2~140
>>
>> So.. it was introduced and removed in 2.6.13 time frame
>>
>>
>> When the counters were removed the sbe_* sbf_* variable
>> declarations were not removed. Hence it caused a little confusion.
>> So I believe these stats were not available and hence can't be
>> considered as regression.
>>
>> 476d139c218e44e045e4bc6d4cc02b010b343939 consolidated the fork and
>> exec balance. Thereafter it became non-trivial to provide separate
>> stats for fork and exec events. So if people think a consolidated
>> balance-on-event is needed, it can be looked into separately. But
>> that shouldn't prevent this documentation cleanup patch from
>> getting in.
>>
>> -Ciju
>>
>>
>> -- 
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>>
> 
> 
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