linux-kernel - Re: [PATCH, v8 1/3] hrtimer: introduce effective timer slack

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Message-ID: <20110304122035.GB14933@shutemov.name>
Date:	Fri, 4 Mar 2011 14:20:35 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Paul Menage <menage@...gle.com>, Li Zefan <lizf@...fujitsu.com>,
	containers@...ts.linux-foundation.org,
	jacob.jun.pan@...ux.intel.com,
	Arjan van de Ven <arjan@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Matt Helsley <matthltc@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-api@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH, v8 1/3] hrtimer: introduce effective timer slack

On Thu, Mar 03, 2011 at 05:32:28PM +0100, Arnd Bergmann wrote:
> On Thursday 03 March 2011, Kirill A. Shutsemov wrote:
> > task_get_effective_timer_slack() returns timer slack value to be used
> > to configure per-task timers. It can be equal or higher than task's
> > timer slack value.
> > 
> > For now task_get_effective_timer_slack() returns timer_slack_ns of the
> > task. Timer slack cgroup controller will implement a bit more
> > sophisticated logic.
> 
> Some time ago, there was a discussion about a method for automatically
> determining timer slack values, and I think nobody ever implemented it.
> 
> The idea was to penalize tasks that have timers expiring a lot, typically
> a sign of programs that were not written with power consumption in mind.
> 
> I think that could be nicely combined with your patch. Instead of setting
> the effective timer slack for the entire control group, you  could
> set a target value that is applied only to tasks that have their timers
> expire frequently. When a timer expires for a task, you increase the
> effective slack up to the maximum, and when you set up a timer, you
> decrease it again. The amount by which the effective slack gets changed
> can depend on how long ago the last timer expired.
> 
> Does this make sense to you?

Hm.. I think we can add this kind of functionality to timer slack cgroup
as a policy/stratagy later. I want to integrate basic functionality to
kernel first.

-- 
 Kirill A. Shutemov
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