linux-kernel - Re: [RFC] vmstat: Avoid waking up idle-cpu to service shepherd work

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Message-ID: <CAKohpo=nTXutbVVf-7iAwtgya4zUL686XbG69ExQ3Pi=VQRE-A@mail.gmail.com>
Date:	Fri, 27 Mar 2015 10:19:54 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	hannes@...xchg.org, Christoph Lameter <cl@...ux.com>,
	Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	vinmenon@...eaurora.org, shashim@...eaurora.org,
	Michal Hocko <mhocko@...e.cz>, mgorman@...e.de,
	dave@...olabs.net, koct9i@...il.com,
	Linux Memory Management List <linux-mm@...ck.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC] vmstat: Avoid waking up idle-cpu to service shepherd work

On 27 March 2015 at 01:48, Andrew Morton <akpm@...ux-foundation.org> wrote:
> Shouldn't this be viewed as a shortcoming of the core timer code?

Yeah, it is. Some (not so pretty) solutions were tried earlier to fix that, but
they are rejected for obviously reasons [1].

> vmstat_shepherd() is merely rescheduling itself with
> schedule_delayed_work().  That's a dead bog simple operation and if
> it's producing suboptimal behaviour then we shouldn't be fixing it with
> elaborate workarounds in the caller?

I understand that, and that's why I sent it as an RFC to get the discussion
started. Does anyone else have got another (acceptable) idea to get this
resolved ?

--
viresh

[1] http://lists.linaro.org/pipermail/linaro-kernel/2013-November/008866.html
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