linux-kernel - Re: proc/stat: idle goes backward

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Message-ID: <20130816151339.GA29675@redhat.com>
Date:	Fri, 16 Aug 2013 17:13:39 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Jaromir Capik <jcapik@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ania Honess <ahoness@...hat.com>, atomlin@...hat.com,
	asolanas@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: proc/stat: idle goes backward

On 08/16, Frederic Weisbecker wrote:
>
> On Fri, Aug 16, 2013 at 04:47:04PM +0200, Oleg Nesterov wrote:
> >
> > Questions:
> >
> > 	- Any other reason why it can be non-monotonic?
> >
> > 	- Should we fix this or should we document that userspace
> > 	  should handle this itself?
> >
> > 	  IOW, is this is bug or not?
>
> I don't know if we want to fix it (I personally think we should because it is not the
> first time I hear complains about this) but if we do, here is a possible fix:
>
> https://lkml.org/lkml/2013/8/8/638

Thanks! it is not easy to read the patches on lkml.org and I do
not understand this code enough. But it seems that this should
address my concerns, including the "even ignoring drivers/cpuidle/".

Except, I am not sure that these changes handle the case when
nr_iowait() change in between.

Are you going to resend?

Oleg.

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