linux-kernel - Re: [stable] 2.6.23 regression: top displaying 9999% CPU usage

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Message-Id: <200710142236.10768.borntraeger@de.ibm.com>
Date:	Sun, 14 Oct 2007 22:36:10 +0200
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Frans Pop <elendil@...net.nl>
Cc:	Greg KH <greg@...ah.com>, stable@...nel.org,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: [stable] 2.6.23 regression: top displaying 9999% CPU usage

Am Samstag, 13. Oktober 2007 schrieb Frans Pop:
> > > Please consider this patch for 2.6.23.2
> > > http://lkml.org/lkml/2007/10/4/389
> > Is it already in Linus's tree?  If so, do you have a git commit id?  If
> > not, please let us (stable@) know when it is, and what the id is, and
> > then we can add it to our tree.
> 
> Not AFAICT.
> CCing Christian (as patch author) and Ingo (as author of the change that 
> caused the regression) so they can push it through the correct channels.
> 

I dont know how to proceed with this issue. The more I think about it, the
more I am convinced that using sum_exec_runtime together with sampled utime
and stime will never guarantee monotonicity for utime and stime in proc. 
Just imagine an process with 9 ticks for utime and 0 ticks for stime. If
we now sample one tick for stime (but having only a small increase in
sum_exec_runtime) the next utime value will only be 90% of the last value. 
So returning to the 2.6.22 model seems to be the safest solution until 
somebody else comes up with an idea that works proper.

Ingo, any opinion?

Christian
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