From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752786AbZGXNQy (ORCPT ); Fri, 24 Jul 2009 09:16:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752469AbZGXNQx (ORCPT ); Fri, 24 Jul 2009 09:16:53 -0400 Received: from one.firstfloor.org ([213.235.205.2]:42889 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752200AbZGXNQx (ORCPT ); Fri, 24 Jul 2009 09:16:53 -0400 Date: Fri, 24 Jul 2009 15:16:49 +0200 From: Andi Kleen To: Thomas Hellstrom Cc: Andi Kleen , "linux-kernel@vger.kernel.org" , "mingo@elte.hu" , "venkatesh.pallipadi@intel.com" Subject: Re: [PATCH] x86: Use clflush() instead of wbinvd() whenever possible when changing mapping Message-ID: <20090724131649.GC2045@basil.fritz.box> References: <1248421981-31865-1-git-send-email-thellstrom@vmware.com> <87ocra1jn6.fsf@basil.nowhere.org> <4A698B3E.4020208@vmware.com> <20090724105831.GB2045@basil.fritz.box> <4A699784.9020803@vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A699784.9020803@vmware.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > No. It was motivated by the assumption that wbinvd() is just bad: Ok, got it now. > Qoute: > > WBINVD is a very nasty operation. I was talking to some CPU people and they > really recommended to get rid of it as far as possible. Stopping the CPU > for msecs is just wrong and there are apparently even some theoretical live > lock situations. - It is not interruptible in earlier VT versions and > messes up real time in the hypervisor. Some people were doing KVM on rt > kernels and had latency spikes from that. > > > /Qoute > (I believe you wrote that ?) Yes. That's still true and that's one reason to not use it. -Andi