linux-kernel - Re: [PATCH 0/3] Reduce length of the eagerfpu path during x86 context switches

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Message-ID: <20140827160335.GD12424@suse.de>
Date:	Wed, 27 Aug 2014 17:03:35 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	H Peter Anvin <hpa@...or.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Mike Galbraith <mgalbraith@...e.de>, Linux-X86 <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] Reduce length of the eagerfpu path during x86
 context switches

On Wed, Aug 06, 2014 at 01:55:45PM +0100, Mel Gorman wrote:
> Eager FPU switching is used on CPUs that support xsave on the grounds
> that CPUs that support it can optimise the switch with xsaveopt and xrstor
> instead of serialising by updating cr0.TS which has serialising semantics.
> 
> The path for eagerfpu is fatter than it needs to be because it still
> maintains the fpu_counter for lazy FPU switches even though the information
> is never used. This patch splits the paths optimises the eagerfpu path a
> little. The benefit is marginal, it was just noticed when looking at why
> integer-only workloads were spending time saving/restoring FPU states.
> 

This was initially sent when it would collide with the merge window
which was stupid timing. Nothing has actually changed since but I wonder
if anyone had a chance to take a look at this patches?

Thanks

-- 
Mel Gorman
SUSE Labs
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