From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757965Ab1EMIF6 (ORCPT ); Fri, 13 May 2011 04:05:58 -0400 Received: from mailout-de.gmx.net ([213.165.64.22]:38939 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1757804Ab1EMIFz (ORCPT ); Fri, 13 May 2011 04:05:55 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1/x8vBKv4nxnknkJj/vBBTMkAjJKypdApBN12D8dr I2hSyy1Kw4RMBs Subject: Re: Sched_autogroup and niced processes From: Mike Galbraith To: Yong Zhang Cc: Carl-Johan Kjellander , linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Date: Fri, 13 May 2011 10:05:50 +0200 Message-ID: <1305273950.15080.7.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 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 Fri, 2011-05-13 at 15:53 +0800, Yong Zhang wrote: > Cc'ing more people. > > On Fri, May 13, 2011 at 3:39 PM, Carl-Johan Kjellander > wrote: > > I've been running seti@home niced to 19 in the background since 1999 > > without any problems. No noticeable effect even when playing a movie > > or a game. But since 2.6.38 the new fix-all-problems automatic > > grouping has been messing a bit with me. These are some timed compiles > > on my 8 cores. Heh, it's not a fix-all-problems thingy, and was never intended to be. It's also not enabled by default. > > time make -j12 # with seti@home running > > real 4m16.753s > > user 10m33.770s > > sys 1m39.710s > > > > time make -j12 # without seti@home running > > real 2m12.480s > > user 10m11.580s > > sys 1m39.980s > > > > echo 0 > /proc/sys/kernel/sched_autogroup_enabled > > time make -j12 # no autogroup, seti@home running again > > real 2m33.276s > > user 10m37.540s > > sys 1m43.190s > > > > All compiles already had all files cached in RAM. > > > > Now I can take the 10% performance hit, but not the 100% hit of > > running stuff super niced in the background. Processes niced to 19 > > should only use spare cycles and not take up half of the cores even > > with autogroup. I would really like to run autogroup since it is a > > neat idea, but it can't mess up running niced processes in the > > background which have been working fine for 12 years. > > Then how about change the nice value of seti@home->autogroup? > echo 19 > /proc/'pid of seti@home'/autogroup Yup. Overhead and whatnot is the dark side of group scheduling. The thing to do is to turn group scheduling off if you don't like what it does for/to you. -Mike