linux-kernel - Re: [patch] CFS scheduler, -v19

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Date:	Mon, 16 Jul 2007 19:59:17 +0200
From:	Markus <lists4me@....de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
Subject: Re: [patch] CFS scheduler, -v19

> > [...] The mouse is smooth, just when one app is being quit (dont 
> > know why...) the mouse will be jerking for a few seconds...
> is the mouse jerky on any app quitting?
No.

> Or is your observation the  following: _sometimes_ apps quit 
> unexpectedly (their window just vanishes?), and _at the same time_,
> the mouse becomes jerky as well, for a few seconds?
Exactly.

> the mouse typically only becomes jerky when there's some really high 
> load on the system - anything else would be a kernel bug. A jerky
> mouse on an unloaded system is definitely a sign of some sort of
> kernel bug  (in or outside of the scheduler). An app vanishing
> unexpectedly might mean an OOM-kill - but that would should up in the
> syslog as well.    
> Pretty weird.
Well, the system uses about 30% of the cpu (cool'n'quite put it on the 
lowest frequency).

I made a plain 2.6.22.1 and could use it for about 2 hours without 
any problem. Then I applied the cfs-v19 for that kernel, rebuild from 
mrproper with the saved config and booted. After a few minutes the 
first app vanished... some more followed by time (I just surfed around 
a bit...)

The dmesg output is not differing in any interesting point (just some 
numbers, like raid-benchmark, some irqs or usb-numbers...)

So its obviously something within cfs... unfortunately...

> Can you make this regression trigger arbitrarily, so that we could
> debug it better? Apps exiting unexpectedly can be debugged via: 
> 
http://kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc6/2.6.22-rc6-mm1/broken-out/vdso-print-fatal-signals.patch
> 
> you can turn it on via the print-fatal-signals=1 boot option or via:
> 
>   echo 1 > /proc/sys/kernel/print-fatal-signals
> 
> this feature will produce a small dump to the syslog about every app 
> that exits unexpectedly. Note that this might not cover all types of 
> "window suddenly vanishes" regressions.
Nothing is printed for a disapeared app for me.


Is there anything more I can try?


   Markus
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