linux-kernel - Re: [patch 2/2] x86,fpu: lazy allocation of FPU area

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Message-ID: <20080224163228.GD27194@linux-os.sc.intel.com>
Date:	Sun, 24 Feb 2008 08:32:29 -0800
From:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Suresh Siddha <suresh.b.siddha@...el.com>, mingo@...e.hu,
	hpa@...or.com, tglx@...utronix.de, linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [patch 2/2] x86,fpu: lazy allocation of FPU area

On Sun, Feb 24, 2008 at 01:20:05PM +0100, Andi Kleen wrote:
> On Sat, Feb 23, 2008 at 06:34:39PM -0800, Suresh Siddha wrote:
> > Only allocate the FPU area when the application actually uses FPU, i.e., in the
> > first lazy FPU trap. This could save memory for non-fpu using apps.
> 
> Did you measure this making any difference? 
> 
> At least at some point glibc always touched the FPU once to initialize
> it.

Simple kernel boot showed that only 20 or so tasks using FPU, out of 
200 or so tasks running.

thanks,
suresh
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