linux-kernel - Re: [PATCH] ipmi: use round_jiffies on timers to reduce timer overhead/wakeups

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Date:	Wed, 21 Oct 2009 11:42:10 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Randy Dunlap <randy.dunlap@...cle.com>
Cc:	discuss@...sWatts.org, lkml <linux-kernel@...r.kernel.org>,
	Corey Minyard <minyard@....org>,
	openipmi-developer@...ts.sourceforge.net
Subject: Re: [PATCH] ipmi: use round_jiffies on timers to reduce timer
 overhead/wakeups

On Wed, 21 Oct 2009 10:28:22 -0700
Randy Dunlap <randy.dunlap@...cle.com> wrote:

> From: Randy Dunlap <randy.dunlap@...cle.com>
> 
> Use a round_jiffies() variant to reduce overhead of timer
> wakeups.  This causes the ipmi timers to occur at the same
> time as other timers (per CPU).
> 
> Typical powertop for /ipmi/ (2.6.31, before patch):
>   11.4% (247.4)            kipmi0 : __mod_timer (process_timeout) 
>    0.6% ( 13.1)       <interrupt> : ipmi_si 
>    0.5% ( 10.0)     <kernel core> : __mod_timer (ipmi_timeout) 
> 
> powertop for /ipmi/, 2.6.31, after patch:
>   10.8% (247.6)            kipmi0 : __mod_timer (process_timeout) 
>    0.3% (  6.9)       <interrupt> : ipmi_si 
>    0.0% (  1.0)     <kernel core> : __mod_timer (ipmi_timeout)

while it is nice that ipmi_si ande the timer wake up less now.... it's
still rather sad that the 247.6 from kipmi0 are still there..... those
are a much much bigger issue

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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