linux-kernel - Re: bad networking related lag in v2.6.22-rc2

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Date:	Mon, 21 May 2007 10:03:51 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Anant Nitya <kernel@...chanda.info>
Cc:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: bad networking related lag in v2.6.22-rc2


* Ingo Molnar <mingo@...e.hu> wrote:

> ok, i got your -rc2 debug numbers (off-list), and it doesnt look pretty:
> 
> before-lag:
> 
>  sleep_max                :           259502076
>  block_max                :            27690921
>  wait_max                 :            16381558
> 
> after-lag:
> 
>  sleep_max                :           584186160
>  block_max                :           261780071
>  wait_max                 :           881255577
> 
> ouch! a nearly 1 second delay got observed by the scheduler - something 
> is really killing your system!
> 
> what does 'top' show during an upload? Is any system related task out 
> of whack? Could you try to get a readprofile or an oprofile output 
> from the kernel, so that we can see what is slowing it down so much? 
> It could be something networking related in v2.6.22-rc2.

ah, you got the latency tracer from Thomas, as part of the -hrt patchset 
- that makes it quite a bit easier to debug. Could you run the attached 
trace-it-10sec utility:

	trace-it-10sec > trace-to-ingo.txt

and send me the (compressed) trace output (off-list, or post an URL to 
the trace)? Try to reproduce the 'lag' event in the 10 seconds while the 
tracer is running.

	Ingo
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