linux-kernel - Re: delayacct regression in 2.6.24 git

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Message-ID: <20071102152529.GB20134@elte.hu>
Date:	Fri, 2 Nov 2007 16:25:29 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Balbir Singh <balbir@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: delayacct regression in 2.6.24 git


* Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:

> Hi, Ingo,
> 
> I missed commit 75d4ef16a6aa84f708188bada182315f80aab6fa
> "sched: fix delay accounting performance regression"
> 
> Without these changes, I find that delay accounting does
> not work as expected, I see zeros in the field for virtual,delay
> and count(s).
> 
> CPU             count     real total  virtual total    delay total
>                     0      535861848              0              0
> 
> 
> This breaks existing delay accounting behaviour.
> 
> Am I missing something?

delay accounting was causing context-switch slowdown because it called 
sched_clock() explicitly - but indeed my fix to that is wrong ...

how about reverting the change but also using rq->clock instead of 
sched_clock()?

	Ingo
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