linux-kernel - Re: [patch 4/4] sched: Distangle worker accounting from rq->lock

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Message-ID: <20110623104455.GA9274@elte.hu>
Date:	Thu, 23 Jun 2011 12:44:55 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Tejun Heo <tj@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Jens Axboe <axboe@...nel.dk>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch 4/4] sched: Distangle worker accounting from rq->lock


* Tejun Heo <tj@...nel.org> wrote:

> The patch description is simply untrue.  It does affect how wq 
> behaves under heavy CPU load.  The effect might be perfectly okay 
> but more likely it will result in subtle suboptimal behaviors under 
> certain load situations which would be difficult to characterize 
> and track down.  Again, the trade off (mostly killing of 
> ttwu_local) could be okay but you can't get away with just claiming 
> "there's no harm".

Well, either it can be measured or not. If you can suggest a specific 
testing method to Thomas, please do.

Thanks,

	Ingo
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