From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752802AbZEUIrs (ORCPT ); Thu, 21 May 2009 04:47:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751723AbZEUIrj (ORCPT ); Thu, 21 May 2009 04:47:39 -0400 Received: from mx2.redhat.com ([66.187.237.31]:44312 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751459AbZEUIri (ORCPT ); Thu, 21 May 2009 04:47:38 -0400 Message-ID: <4A15151A.6000708@redhat.com> Date: Thu, 21 May 2009 11:47:22 +0300 From: Avi Kivity User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Mark Langsdorf CC: Joerg Roedel , peterz@infradead.org, Ingo Molnar , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH][KVM][retry 4] Add support for Pause Filtering to AMD SVM References: <200905050909.58583.mark.langsdorf@amd.com> <200905081203.55484.mark.langsdorf@amd.com> <200905191356.37071.mark.langsdorf@amd.com> <200905201725.18046.mark.langsdorf@amd.com> In-Reply-To: <200905201725.18046.mark.langsdorf@amd.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Mark Langsdorf wrote: > This feature creates a new field in the VMCB called Pause > Filter Count. If Pause Filter Count is greater than 0 and > intercepting PAUSEs is enabled, the processor will increment > an internal counter when a PAUSE instruction occurs instead > of intercepting. When the internal counter reaches the > Pause Filter Count value, a PAUSE intercept will occur. > > This feature can be used to detect contended spinlocks, > especially when the lock holding VCPU is not scheduled. > Rescheduling another VCPU prevents the VCPU seeking the > lock from wasting its quantum by spinning idly. Perform > the reschedule by increasing the the credited time on > the VCPU. > > Experimental results show that most spinlocks are held > for less than 1000 PAUSE cycles or more than a few > thousand. Default the Pause Filter Counter to 3000 to > detect the contended spinlocks. > > Processor support for this feature is indicated by a CPUID > bit. > > On a 24 core system running 4 guests each with 16 VCPUs, > this patch improved overall performance of each guest's > 32 job kernbench by approximately 1%. Further performance > improvement may be possible with a more sophisticated > yield algorithm. > Please split this into a scheduler patch and a kvm patch. -- error compiling committee.c: too many arguments to function