linux-kernel - RE: What's the right value for idle= (was: Re: [linux-pm] regression on P-II SMP)

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Date:	Sun, 21 Feb 2010 13:02:19 -0800
From:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Guennadi Liakhovetski <g.liakhovetski@....de>
CC:	"linux-pm@...ts.linux-foundation.org" 
	<linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	Arjan van de Ven <arjan@...radead.org>
Subject: RE: What's the right value for idle= (was: Re: [linux-pm]
 regression on P-II SMP)

 

>-----Original Message-----
>From: Rafael J. Wysocki [mailto:rjw@...k.pl] 
>Sent: Sunday, February 21, 2010 12:36 PM
>To: Guennadi Liakhovetski
>Cc: linux-pm@...ts.linux-foundation.org; LKML; ACPI Devel 
>Maling List; Pallipadi, Venkatesh; Len Brown; Arjan van de Ven
>Subject: What's the right value for idle= (was: Re: [linux-pm] 
>regression on P-II SMP)
>
>On Sunday 21 February 2010, Guennadi Liakhovetski wrote:
>> Hi
>> 
>> my 2xP-II@...MHz locks up with 2.6.32(.X) unless I specify 
>"idle=*" on the 
>> kernel command-line, where "*" is one of "poll," "mwait," 
>"halt," and only 
>> "nomwait" indeed locks it up. Last kernel known to work was 
>2.6.25. So, it 
>> doesn't bother me all that much - I have a way to boot it, but maybe 
>> someone would be interested to fix this (this system already 
>has a few 
>> quirks on the kernel command line, so, one more doesn't 
>really hurt;)). 
>> What interests me more - which of those shall I be using? From 
>> Documentation/kernel-parameters.txt it looks like "mwait" 
>should be best 
>> for me? Or should I be using "halt?" "Poll" does indeed fry 
>CPUs - raises 
>> sys temperatures to 50 / 60 degrees C. Power-saving is not 
>that much of a 
>> concern for me - I only run that system occasionally, but it 
>shouldn't 
>> produce more heat than it must;) And since this system does 
>have a broken 
>> ACPI (Compaq AP400), I wouldn't try to be too smart with it.
>
>I guess "mwait" is the right one, but let's try to ask experts.
>

This CPU doesn't support mwait. So, idle=halt is what you should be using. That said, halt based idle is what should be used on this system by default, unless it supports ACPI based C-states. Can you send in the dmesg, with 2.6.25 without any boot parameter.

Thanks,
Venki--
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