From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754055Ab1LTBzj (ORCPT ); Mon, 19 Dec 2011 20:55:39 -0500 Received: from e23smtp09.au.ibm.com ([202.81.31.142]:54974 "EHLO e23smtp09.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752481Ab1LTBzh (ORCPT ); Mon, 19 Dec 2011 20:55:37 -0500 From: Nikunj A Dadhania To: Peter Zijlstra Cc: mingo@elte.hu, linux-kernel@vger.kernel.org, vatsa@linux.vnet.ibm.com, bharata@linux.vnet.ibm.com, Benjamin Herrenschmidt , paulus Subject: Re: [RFC PATCH 0/4] Gang scheduling in CFS In-Reply-To: <1324309901.24621.14.camel@twins> References: <20111219083141.32311.9429.stgit@abhimanyu.in.ibm.com> <1324309901.24621.14.camel@twins> User-Agent: Notmuch/0.10.2+70~gf0e0053 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-redhat-linux-gnu) Date: Tue, 20 Dec 2011 07:26:18 +0530 Message-ID: <874nww2egt.fsf@abhimanyu.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii x-cbid: 11121916-3568-0000-0000-000000E9779E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 19 Dec 2011 16:51:41 +0100, Peter Zijlstra wrote: > > Anyway, I had a look at your patches and I don't see how could ever > work. You gang-schedule cgroup entities, but there's no guarantee the > load-balancer will have at least one task for each group on every cpu. > As stated earlier: The gang scheduling problem can be broken into two parts: a) Placement of the tasks to be gang scheduled b) Synchronized scheduling of the tasks across a subset of cpu. In the patch, I have (b) implemented and placement is done by pinning the vcpu of a VM in userspace. Yes, thats not the right way. Effectively, no trouble to the load-balancer here. Nikunj