From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935233AbaH0RD1 (ORCPT ); Wed, 27 Aug 2014 13:03:27 -0400 Received: from terminus.zytor.com ([198.137.202.10]:48207 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932437AbaH0RD0 (ORCPT ); Wed, 27 Aug 2014 13:03:26 -0400 Message-ID: <53FE0F46.5010001@zytor.com> Date: Wed, 27 Aug 2014 10:03:02 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 MIME-Version: 1.0 To: Mel Gorman , Suresh Siddha CC: Mike Galbraith , Linux-X86 , LKML Subject: Re: [PATCH 0/3] Reduce length of the eagerfpu path during x86 context switches References: <1407329748-3928-1-git-send-email-mgorman@suse.de> <20140827160335.GD12424@suse.de> In-Reply-To: <20140827160335.GD12424@suse.de> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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