linux-kernel - Re: [patch] change futex

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Message-ID: <20070312105826.GB11864@one.firstfloor.org>
Date:	Mon, 12 Mar 2007 11:58:26 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Roland McGrath <roland@...hat.com>, akpm@...ux-foundation.org,
	mm-commits@...r.kernel.org, npiggin@...e.de, drepper@...hat.com,
	oleg@...sign.ru, sebastien.dugue@...l.net,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] change futex_wait() to hrtimers

On Mon, Mar 12, 2007 at 12:00:20PM +0100, Thomas Gleixner wrote:
> On Mon, 2007-03-12 at 12:27 +0100, Andi Kleen wrote:
> > Ingo Molnar <mingo@...e.hu> writes:
> > > 
> > > the only correct approach is the use of hrtimers, and a patch exists for 
> > > that - see below. This has been included in -rt for quite some time.
> > 
> > But isn't that bad for power management? You'll likely get more
> > idle wakeups, won't you?
> 
> Why so ? It comes more precise, but only once.

When it's clustered around the jiffies interval then wakeups from
multiple processes will be somewhat batched. With a precise wakeup you'll
get wakeups all over the jiffies period, won't you?

-Andi
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