From: "H. Peter Anvin" <hpa@zytor.com>
To: Mel Gorman <mgorman@suse.de>, Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Mike Galbraith <mgalbraith@suse.de>, Linux-X86 <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/3] Reduce length of the eagerfpu path during x86 context switches
Date: Wed, 27 Aug 2014 10:03:02 -0700 [thread overview]
Message-ID: <53FE0F46.5010001@zytor.com> (raw)
In-Reply-To: <20140827160335.GD12424@suse.de>
On 08/27/2014 09:03 AM, Mel Gorman wrote:
> 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?
>
Looking at it now.
-hpa
next prev parent reply other threads:[~2014-08-27 17:03 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-06 12:55 [PATCH 0/3] Reduce length of the eagerfpu path during x86 context switches Mel Gorman
2014-08-06 12:55 ` [PATCH 1/3] x86, fpu: Do not copy fpu preload state Mel Gorman
2014-08-06 12:55 ` [PATCH 2/3] x86, fpu: Split FPU save state preparation into eagerfpu and !eagerfpu parts Mel Gorman
2014-08-06 12:55 ` [PATCH 3/3] x86, fpu: Do not update fpu_counter in the eagerfpu case Mel Gorman
2014-08-27 16:03 ` [PATCH 0/3] Reduce length of the eagerfpu path during x86 context switches Mel Gorman
2014-08-27 17:03 ` H. Peter Anvin [this message]
-- strict thread matches above, loose matches on Subject: below --
2014-08-06 12:55 Mel Gorman
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