From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752479AbYBSGKl (ORCPT ); Tue, 19 Feb 2008 01:10:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752528AbYBSGK1 (ORCPT ); Tue, 19 Feb 2008 01:10:27 -0500 Received: from mail.gmx.net ([213.165.64.20]:42244 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752154AbYBSGK0 (ORCPT ); Tue, 19 Feb 2008 01:10:26 -0500 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1+4GeBj7xS4WWKnfGegcKqvWCy8IhqChLIO/w3pGV f8lhY5todASJ9N Subject: Re: [PATCH 0/7] Single RQ group scheduling From: Mike Galbraith To: Peter Zijlstra Cc: Ingo Molnar , Srivatsa Vaddagiri , dhaval@linux.vnet.ibm.com, tong.n.li@intel.com, linux-kernel@vger.kernel.org In-Reply-To: <20080218095535.629736000@chello.nl> References: <20080218095535.629736000@chello.nl> Content-Type: text/plain Date: Tue, 19 Feb 2008 07:10:21 +0100 Message-Id: <1203401421.4252.13.camel@homer.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.12.0 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2008-02-18 at 10:55 +0100, Peter Zijlstra wrote: > This is my current queue for single RQ group scheduling. I took these out for a brief maxcpus=1 spin yesterday, and noticed something. Running 4 copies of chew-max, one as a user, the context switch rate was high (~1800/s). I increased sched_min_granularity_ns to see if that would lower it, and it did, but it also upset fairness. With sched_min_granularity_ns bumped to half of sched_latency_ns (40ms default) it was a largish skew. top - 06:58:46 up 3 min, 15 users, load average: 4.71, 2.53, 1.04 Tasks: 214 total, 9 running, 204 sleeping, 0 stopped, 1 zombie Cpu(s): 39.0%us, 61.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ P COMMAND 5389 mikeg 20 0 1464 364 304 R 40.1 0.0 0:29.71 0 chew-max 5373 root 20 0 1464 364 304 R 19.0 0.0 0:16.30 0 chew-max 5388 root 20 0 1464 364 304 R 19.0 0.0 0:15.79 0 chew-max 5374 root 20 0 1464 364 304 R 18.6 0.0 0:15.90 0 chew-max -Mike