linux-kernel - Re: [PATCH v5 3/3] sched/cputime: Add steal time support to full dynticks CPU time accounting

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Message-ID: <CANRm+Cwa9WMLV+7PKLf_JVwn_TuSxPYuM7mc5-8KAvdXabCZ7g@mail.gmail.com>
Date:	Wed, 8 Jun 2016 15:27:58 +0800
From:	Wanpeng Li <kernellwp@...il.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Rik van Riel <riel@...hat.com>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kvm <kvm@...r.kernel.org>, Wanpeng Li <wanpeng.li@...mail.com>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH v5 3/3] sched/cputime: Add steal time support to full
 dynticks CPU time accounting

2016-06-08 15:22 GMT+08:00 Ingo Molnar <mingo@...nel.org>:
>
> * Wanpeng Li <kernellwp@...il.com> wrote:
>
>> From: Wanpeng Li <wanpeng.li@...mail.com>
>>
>> This patch adds guest steal-time support to full dynticks CPU
>> time accounting. After the following commit:
>>
>> ff9a9b4c4334 ("sched, time: Switch VIRT_CPU_ACCOUNTING_GEN to jiffy granularity")
>>
>> ... time sampling became jiffy based, even if it's still listened
>> to ring boundaries, so steal_account_process_tick() is reused
>> to account how many 'ticks' are stolen-time, after the last accumulation.
>
> So the 'ring boundary' part still doesn't parse (neither grammatically nor
> logically) - please rephrase it because I have no idea what you want to say here.

It is original from this slides.
http://ertl.jp/~shinpei/conf/ospert13/slides/FredericWeisbecker.pdf,
slide 28.

>
> Did you want to say:
>
>> ... time sampling became jiffy based, even if it's still being context tracked,
>> so steal_account_process_tick() is reused to account how many 'ticks' are
>> stolen-time, after the last accumulation.
>
> ... which makes sense grammatically but does not make sense to me logically. :-/
>
> Rik, Frederic, could you please help out?
>
> Thanks,
>
>         Ingo