linux-kernel - RE: [PATCH V2] watchdog: optimizing the hrtimer interval for power saving

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Message-ID: <27240C0AC20F114CBF8149A2696CBE4A1DD2BA@SHSMSX101.ccr.corp.intel.com>
Date:	Thu, 29 Nov 2012 00:30:30 +0000
From:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
To:	Don Zickus <dzickus@...hat.com>
CC:	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"mingo@...nel.org" <mingo@...nel.org>, "rjw@...k.pl" <rjw@...k.pl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V2] watchdog: optimizing the hrtimer interval for power
 saving

> It seems like a better approach would be to adjust the timer somehow when
> you change c-states.  The whole point of the hard and softlockup is to
> detect if scheduled code is either deadlock or hogging the cpu for too long.
> 
> If the cpu is in a deep sleep, then nothing is running, right?  Which
> means nothing can deadlock or hog the cpu.  In those cases you can
> probably temporarily disable the lockup detector until the cpu wakes up
> from that c-state and starts scheduling code again.
> 
You are right, I ever tried the thought, when CPU is idle, we can pause the hrtimer,
After wakeup, we resume the hrtimer again. But I found sometimes the in idle and out of
idle is too frequent.
Anyway, you advice seems the right way, I will try to dig something more deeply.
Thanks.
> In that case you can really maximize your power savings (and probably get
> powerTop to stop telling everyone to disable the nmi_watchdog :-) ).
> 
> Ideally in a deep sleep you don't want any soft interrupts running, no?
> 
> Just a thought.
> 
> Cheers,
> Don
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