Date: Tue, 4 Mar 2008 18:29:18 +0100
From: Andi Kleen <andi@firstfloor.org>
To: Pierre Ossman <drzeus-list@drzeus.cx>
Cc: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>,
       Dave Jones <davej@codemonkey.org.uk>, Andi Kleen <andi@firstfloor.org>,
       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
Message-ID: <20080304172918.GA27332@one.firstfloor.org>
References: <924EFEDD5F540B4284297C4DC59F3DEEA2E8B2@orsmsx423.amr.corp.intel.com> <Pine.LNX.4.44L0.0803031804330.8280-100000@iolanthe.rowland.org> <20080303231033.GB15255@one.firstfloor.org> <20080304040048.GA31562@codemonkey.org.uk> <20080304071423.0e6b71c1@mjolnir.drzeus.cx> <20080304181924.70aaf8c1@mjolnir.drzeus.cx>
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> So for now, I'm back to thinking that measuring the interval between deep sleeps is the better approach. I could use some ideas for a good clock source though. I haven't dug much deeper than jiffies when it comes to kernel timekeeping.

jiffies should work, you just need to make sure you measure them at the
right place. In particular there is some code in dyntick that catches
up on jiffies after the deep sleep when the normal timer handler didn't run
and jiffies are only usable again after that code executed.

-ANdi
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