linux-kernel - Re: [PATCH] cputime: fix invalid gtime

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Date:	Thu, 17 Sep 2015 16:21:44 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH] cputime: fix invalid gtime

On Thu, Sep 03, 2015 at 12:45:50AM +0000, Hiroshi Shimamoto wrote:
> From: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
> 
> /proc/stats shows invalid gtime when the thread is running in guest.

Why is this a problem?

> When vtime accounting is not enabled, we cannot get a valid delta.
> Just return gtime when vtime accounting is not enabled in task_gtime().

But isn't other stuff then also broken, like fetch_task_cputime(). Tell
me more about why you think your patch is the right one.

> Before
> 10987 (qemu-kvm) S 1 10923 10923 0 -1 138428608 7521 0 90 0 3776 460 0 0 20 0 24 0 11960 8090398720 151288 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 9 0 0 0 3554 0 0 0 0 0 0 0 0 0

It would have been helpful if you'd used a small script to take out the
right column. As is I've no clue which field to look at.
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