linux-kernel - Re: [PATCH] Greatly improve TSC calibration using a delayed workqueue

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Message-ID: <20101109134355.GA29433@basil.fritz.box>
Date:	Tue, 9 Nov 2010 14:43:55 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	john stultz <johnstul@...ibm.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Clark Williams <williams@...hat.com>
Subject: Re: [PATCH] Greatly improve TSC calibration using a delayed
 workqueue

> Interesting. Thanks for pointing that out! Couldn't I just start the
> calibration after fs_initcall (when the hpet_late_init runs) to avoid
> this as well? 

Yes that probably would work.  Or use the barrier infrastructure 
in workqueue.c

> 
> > Another issue may be races against suspend, but that may be too
> > obscure.
> 
> Yea, that seems fairly obscure. Basically you'd have to suspend in the
> first second as the system came up. In that case the code will throw out
> any calibration refinement that's over 1% off of the initial boot
> calibration, so I think this is ok trade off.

It may happen with opportunistic suspend if the system boots very fast.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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