linux-kernel - Re: [RFC PATCH 11/11] nohz,kvm,time: teach account_process

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Message-ID: <CALCETrV-J1dc-gmqq+-dJUQsiR2Va-zHF2mgij73cd6e1LnN4A@mail.gmail.com>
Date:	Wed, 24 Jun 2015 08:06:49 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Rik van Riel <riel@...hat.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	fweisbec@...hat.com, Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH 11/11] nohz,kvm,time: teach account_process_tick about
 guest time

On Wed, Jun 24, 2015 at 7:58 AM,  <riel@...hat.com> wrote:
> From: Rik van Riel <riel@...hat.com>
>
> When tick based accounting is run from a remote CPU, it is actually
> possible to encounter a task with PF_VCPU set. Make sure to account
> those as guest time.

Why do we have PF_VCPU and CONTEXT_GUEST?  What's the difference
between them (other than the fact that one is per-task and one is
per-cpu)?  It would be a bit easier to understand if there were fewer
of these things.

If the issue is that remote sampling would otherwise have a race that
could account guest time to the wrong task, then maybe PF_VCPU makes
sense.  Hmm.

--Andy
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