From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751574Ab1ADGma (ORCPT ); Tue, 4 Jan 2011 01:42:30 -0500 Received: from mailout-de.gmx.net ([213.165.64.23]:47996 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with SMTP id S1750886Ab1ADGm2 (ORCPT ); Tue, 4 Jan 2011 01:42:28 -0500 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1+ZM/Vh2Q6ZGyy3qV3Wj8QUnuDLQebgmdNZFYMRpd 9KOuBZUyPbul4k Subject: Re: [RFC -v3 PATCH 0/3] directed yield for Pause Loop Exiting From: Mike Galbraith To: Rik van Riel Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Avi Kiviti , Srivatsa Vaddagiri , Peter Zijlstra , Chris Wright In-Reply-To: <20110103162637.29f23c40@annuminas.surriel.com> References: <20110103162637.29f23c40@annuminas.surriel.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 04 Jan 2011 07:42:15 +0100 Message-ID: <1294123335.11283.26.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.30.1.2 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A couple questions. On Mon, 2011-01-03 at 16:26 -0500, Rik van Riel wrote: > When running SMP virtual machines, it is possible for one VCPU to be > spinning on a spinlock, while the VCPU that holds the spinlock is not > currently running, because the host scheduler preempted it to run > something else. Do you have any numbers? If I were to, say, run a 256 CPU VM on my quad, would this help me get more hackbench or whatever oomph from my (256X80386/20:) box? > Both Intel and AMD CPUs have a feature that detects when a virtual > CPU is spinning on a lock and will trap to the host. Does an Intel Q6600 have this trap gizmo (iow will this do anything at all for my little box if I were to try it out). -Mike