Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754999AbYKQVTi (ORCPT ); Mon, 17 Nov 2008 16:19:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752657AbYKQVT1 (ORCPT ); Mon, 17 Nov 2008 16:19:27 -0500 Received: from zrtps0kp.nortel.com ([47.140.192.56]:42601 "EHLO zrtps0kp.nortel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754717AbYKQVT0 (ORCPT ); Mon, 17 Nov 2008 16:19:26 -0500 Message-ID: <4921DFD8.9060509@nortel.com> Date: Mon, 17 Nov 2008 15:19:20 -0600 From: "Chris Friesen" User-Agent: Thunderbird 2.0.0.17 (X11/20080914) MIME-Version: 1.0 To: Ken Chen CC: Ingo Molnar , Peter Zijlstra , Linux Kernel Mailing List Subject: Re: busted CFS group load balancer? References: <20081115011452.GA28135@google.com> <49218FB4.6090805@nortel.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 17 Nov 2008 21:19:22.0480 (UTC) FILETIME=[29116700:01C948FA] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1416 Lines: 31 Ken Chen wrote: > On Mon, Nov 17, 2008 at 7:37 AM, Chris Friesen wrote: >>> It appears that the fair-group load balancer in 2.6.27 does not work >>> properly. >> There was an issue fixed post 2.6.27 where the load balancer didn't work >> properly if there was one task per group per cpu. You might try >> backporting commit 38736f4 and see if that helps. > > Tested git commit 38736f4, it doesn't fix the problem I'm seeing. > I plugged in the same weights into my test app (groups 1 and 2 instead of ant/bee) and got the results below for a 10-sec run. The "actual" numbers give the overall average and then the values for each hog separately. In this case we see that both tasks in group 2 ended up sharing a cpu with one of the tasks from group 1. group actual(%) expected(%) ctx switches max_latency(ms) 1 99.69(99.38/99.99) 99.81 160/262 4/0 2 0.31( 0.31/0.31) 0.19 32/33 391/375 I've only got a 2-way system. If the results really are that much worse on larger systems, then that's going to cause problems for us as well. I'll see if I can get some time on a bigger machine. Chris -- 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/