Re: [linux-pm] [PATCH] cpuidle: avoid singing capacitors

From: Andi Kleen <andi@firstfloor.org>
To: Pierre Ossman <drzeus-list@drzeus.cx>
Cc: Andi Kleen <andi@firstfloor.org>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>,
	Dave Jones <davej@codemonkey.org.uk>,
	Alan Stern <stern@rowland.harvard.edu>,
	LKML <linux-kernel@vger.kernel.org>,
	Adam Belay <abelay@novell.com>, Lee Revell <rlrevell@joe-job.com>,
	linux-pm@lists.linux-foundation.org, Pavel Machek <pavel@ucw.cz>
Subject: Re: [linux-pm] [PATCH] cpuidle: avoid singing capacitors
Date: Tue, 4 Mar 2008 19:34:06 +0100	[thread overview]
Message-ID: <20080304183406.GC27332@one.firstfloor.org> (raw)
In-Reply-To: <20080304190446.775165e3@mjolnir.drzeus.cx>

On Tue, Mar 04, 2008 at 07:04:46PM +0100, Pierre Ossman wrote:
> On Tue, 4 Mar 2008 18:43:15 +0100
> Andi Kleen <andi@firstfloor.org> wrote:
> 
> > > And how can I tell if this handler has run? Not that it really matters I guess, as I don't think running it from the cpuidle governor is very sane.
> >  
> > After irq_enter->tick_nohz_update_jiffies() 
> > 
> > You might need a new callback into the idle governours for this though.
> > 
> 
> I don't think I quite see the point. If we can't force an update, then
> it doesn't really help us knowing if the jiffies value is stale or not.

What do you mean with force an update? The system always does an 
jiffies update automatically after idle wakeup. It's just that if you add 
code to the code path that uses jiffies you have to make sure it is after the 
standard update, otherwise you'll see a stale value.

-Andi