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

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Message-ID: <4ADF57D7.7010808@intel.com>
Date:	Wed, 21 Oct 2009 11:49:59 -0700
From:	"Kok, Auke" <auke-jan.h.kok@...el.com>
To:	Arjan van de Ven <arjan@...ux.intel.com>
CC:	Randy Dunlap <randy.dunlap@...cle.com>,
	"discuss@...sWatts.org" <discuss@...sWatts.org>,
	"openipmi-developer@...ts.sourceforge.net" 
	<openipmi-developer@...ts.sourceforge.net>,
	lkml <linux-kernel@...r.kernel.org>,
	Corey Minyard <minyard@....org>
Subject: Re: [Discuss] [PATCH] ipmi: use round_jiffies on timers to reduce
 timer overhead/wakeups

Arjan van de Ven wrote:
> 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

obviously :)

Randy, any idea where those are coming from ?

Auke


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