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

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Date:	Mon, 31 Jan 2011 09:40:47 +0530
From:	Ciju Rajan K <ciju@...ux.vnet.ibm.com>
To:	Satoru Takeuchi <takeuchi_satoru@...fujitsu.com>
CC:	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	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 Satoru,

> 
> This patch is logically correct, succeeded to compile and works
> fine. But I came to be worried about whether it is good to kill
> all fields you said after reading old and upstream scheduler
> code again.
> 
> 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.
> 

sbe_* & sbf_* flags are added by the commit
68767a0ae428801649d510d9a65bb71feed44dd1  Git describe shows that it was
gone in to v2.6.12-1422-g68767a0  which is quite old. So in my opinion
this might not be a regression.

> # although I haven't been able to notice they are always zero ;-(
> 
> I prefer not to remove these fields({sbe,sbf}_*) but to add
> accounting code for these flags again. What do you think?

I will go through the code and verify once again.

-Ciju

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