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

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Date:	Wed,  6 Aug 2014 13:55:45 +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>, Mel Gorman <mgorman@...e.de>
Subject: [PATCH 0/3] Reduce length of the eagerfpu path during x86 context switches

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.

 arch/x86/include/asm/fpu-internal.h | 46 +++++++++++++++++++++++++++++--------
 arch/x86/kernel/process_32.c        |  2 +-
 arch/x86/kernel/process_64.c        |  2 +-
 3 files changed, 38 insertions(+), 12 deletions(-)

-- 
1.8.4.5

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