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

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Message-Id: <200710292133.48125.borntraeger@de.ibm.com>
Date:	Mon, 29 Oct 2007 21:33:48 +0100
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	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

Am Montag, 29. Oktober 2007 schrieb Ingo Molnar:
> i've got a patch from Peter queued up. (see below) This should fix the 
> main issue.
[...]
> --- linux.orig/fs/proc/array.c
> +++ linux/fs/proc/array.c
> @@ -358,7 +358,8 @@ static cputime_t task_utime(struct task_
>  	}
>  	utime = (clock_t)temp;
> 
> -	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?

Christian



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