From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757165Ab2FDNHv (ORCPT ); Mon, 4 Jun 2012 09:07:51 -0400 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:35991 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753531Ab2FDNHt (ORCPT ); Mon, 4 Jun 2012 09:07:49 -0400 Date: Mon, 4 Jun 2012 18:37:41 +0530 From: Srivatsa Vaddagiri To: Mike Galbraith Cc: Peter Zijlstra , Prashanth Nageshappa , mingo@kernel.org, LKML , roland@kernel.org, Ingo Molnar Subject: Re: [PATCH] sched: balance_cpu to consider other cpus in its group as target of (pinned) task migration Message-ID: <20120604130740.GC25126@linux.vnet.ibm.com> Reply-To: Srivatsa Vaddagiri References: <4FCC4E3B.4090209@linux.vnet.ibm.com> <1338801907.7356.163.camel@marge.simpson.net> <1338810796.28282.32.camel@twins> <1338814063.7356.192.camel@marge.simpson.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1338814063.7356.192.camel@marge.simpson.net> User-Agent: Mutt/1.5.21 (2010-09-15) x-cbid: 12060413-9574-0000-0000-0000030A1FF5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Mike Galbraith [2012-06-04 14:47:43]: > You need a good reason to run RT, and being able to starve others to > death ain't it, so I don't see a good reason to care about the 95% case > enough to fiddle with load balancing to accommodate the oddball case. While starvation of SCHED_OTHER task was an extreme case, the point remains that SCHED_OTHER tasks are better served by moving them away from cpus running rt tasks that are partially cpu intensive. While the current code has the nuts and bolts to recognize this situation (scale_rt_power), it fails to effect SCHED_OTHER task movement because of how one cpu from a sched_group is designated to pull tasks on behalf of its siblings and that chosen balance_cpu may not be in the task's cpus_allowed mask (but the task can run on one or more of its sibling cpus). - vatsa