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

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Message-Id: <1193692264.5644.82.camel@lappy>
Date:	Mon, 29 Oct 2007 22:11:04 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Christian Borntraeger <borntraeger@...ibm.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Frans Pop <elendil@...net.nl>,
	Chuck Ebbert <cebbert@...hat.com>, Greg KH <greg@...ah.com>,
	stable@...nel.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [stable] 2.6.23 regression: top displaying 9999% CPU usage


On Mon, 2007-10-29 at 21:41 +0100, Ingo Molnar wrote:
> * Christian Borntraeger <borntraeger@...ibm.com> wrote:
> 
> > > -	return clock_t_to_cputime(utime);
> > > +	p->prev_utime = max(p->prev_utime, clock_t_to_cputime(utime));
> > > +	return p->prev_utime;
> > >  }
> > [...]
> > 
> > I dont think it will work. It will make utime monotic, but stime can 
> > still decrease. For example let sum_exec_runtime increase by a tiny 
> > little bit while utime will get a full additional tick. stime is 
> > sum-utime. So stime can still go backwards. So I think that we need 
> > this kind of logic for stime as well, no?
> 
> yeah, probably. Peter?

/me dons the brown paper bag while mumbling an agreement of sorts.

I'll not attempt to come up with a patch as I fear I'll just make a
bigger mess in my current state, hope to feel better tomorrow..

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