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

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Message-ID: <20080306192653.GI28006@linux-os.sc.intel.com>
Date:	Thu, 6 Mar 2008 11:26:53 -0800
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Suresh Siddha <suresh.b.siddha@...el.com>, mingo@...e.hu,
	hpa@...or.com, tglx@...utronix.de, andi@...stfloor.org,
	hch@...radead.org, 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 - v3

On Wed, Mar 05, 2008 at 08:48:01PM +0100, Pavel Machek wrote:
> On Mon 2008-03-03 15:02:46, 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.
> 
> How many such apps are on your system, and how much does this
> 'optimalization' cost?

On a normal kernel boot, where there are 200 or so tasks running, only 20
or so apps seem to be using FPU.

> ISTR glibc always using FPU...?

Apparently not, alteast not on my system. And also going forward, as we extend
this state, thought is nice to have.

thanks,
suresh
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