Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933169Ab2EWIKs (ORCPT ); Wed, 23 May 2012 04:10:48 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:57253 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757182Ab2EWIKo convert rfc822-to-8bit (ORCPT ); Wed, 23 May 2012 04:10:44 -0400 MIME-Version: 1.0 In-Reply-To: <1337759644.9698.49.camel@twins> References: <1337754751-9018-1-git-send-email-kernelfans@gmail.com> <1337754751-9018-2-git-send-email-kernelfans@gmail.com> <1337759644.9698.49.camel@twins> Date: Wed, 23 May 2012 16:10:43 +0800 Message-ID: Subject: Re: [PATCH 1/2] sched: add virt sched domain for the guest From: Liu ping fan To: Peter Zijlstra Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, Ingo Molnar , Avi Kivity , Anthony Liguori Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1678 Lines: 37 On Wed, May 23, 2012 at 3:54 PM, Peter Zijlstra wrote: > On Wed, 2012-05-23 at 14:32 +0800, Liu Ping Fan wrote: >> From: Liu Ping Fan >> >> The guest's scheduler can not see the numa info on the host and >> this will result to the following scene: >>   Supposing vcpu-a on nodeA, vcpu-b on nodeB, when load balance, >> the tasks' pull and push between these vcpus will cost more. But >> unfortunately, currently, the guest is just blind to this. >> >> This patch want to export the host numa info to the guest, and help >> guest to rebuild its sched domain based on host's info. > > Hell no, we're not going to export sched domains, if kvm/qemu wants this > its all in sysfs. > > The whole sched_domain stuff is a big enough pain as it is, exporting > this and making it a sodding API is the worst thing ever. > > Whatever brainfart made you think this is needed anyway? sysfs contains > the host topology, qemu can already create whatever guest topology you > want (see the -smp and -numa arguments), so what gives? I think -numa option will be used to emulate the special virtual machine to customer, and do not necessary map to host topology. And even we map them exactly with -numa option, the movement of vcpu threads among host nodes will break the topology initialized by -numa option. So give the guest a opportunity to adjust its topology? Thanks and regards, pingfan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/