From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756122Ab0JAJsY (ORCPT ); Fri, 1 Oct 2010 05:48:24 -0400 Received: from mail-qy0-f181.google.com ([209.85.216.181]:47407 "EHLO mail-qy0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754966Ab0JAJsW (ORCPT ); Fri, 1 Oct 2010 05:48:22 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=SKN1d+TPxQ4dYNABAWPeUxjrmaCeGQImLcp8Ra9tabjW491TLZnGdhf5RyxJlzePiG mKvGJLi4tmrrG7wU/d5G7hCHamn71lp7k9SpbKvf5Vy+ltRfJv9ruUtY/gFFJ2Ec2WCo fxl4ssRpg0c7H0ynD5RH79qX1JI7+jUr8yBpM= Date: Fri, 1 Oct 2010 05:48:14 -0400 From: tmhikaru@gmail.com To: Florian Mickler , linux-kernel@vger.kernel.org, Greg KH Subject: Re: PROBLEM: Unusually high load average when idle in 2.6.35, 2.6.35.1 and later Message-ID: <20101001094814.GA5029@roll> References: <20101001035321.GA2360@roll> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="zYM0uCDKw75PZbzx" Content-Disposition: inline In-Reply-To: <20101001035321.GA2360@roll> User-Agent: Mutt/1.4.2.3i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --zYM0uCDKw75PZbzx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline I was asked to do compile tests since I noticed performance regressions due to my high loadavg issues. For these tests, I've disabled ccache so they should be fair. The software being compiled is linux kernel 2.6.35.6 with my normal kernel configuration file. For the record, the only reason I have XZ_OPT="" is to disable this, from my .bashrc: declare -x XZ_OPT="-e --memory=1GiB" which winds up being taken as an option to lzma, and causes unbootable kernels for my computer. Not exactly what I want, so that's why I do that. I was asked by con kolivas to do allnoconfig builds, but I wound up doing the longer tests I'd been planning to originally since the differences between the two allnoconfig kernel builds seemed to be simply noise. As you can see from the below timed runs though, it appears I have a greater mystery on my hands: BAD kernel timings: # bad: [74f5187ac873042f502227701ed1727e7c5fbfa9] sched: Cure load average vs NO_HZ woes make mrproper && cp ../Hikaruconfig .config && XZ_OPT="" CCACHE_DISABLE="1" time make oldconfig bzImage modules 5680.36user 516.93system 1:51:34elapsed 92%CPU (0avgtext+0avgdata 738000maxresident)k 486208inputs+1991416outputs (254major+106505950minor)pagefaults 0swaps make mrproper && XZ_OPT="" CCACHE_DISABLE="1" time make allnoconfig 5.45user 0.47system 0:06.19elapsed 95%CPU (0avgtext+0avgdata 95888maxresident)k 0inputs+1920outputs (0major+126579minor)pagefaults 0swaps GOOD kernel timings: # good: [09a40af5240de02d848247ab82440ad75b31ab11] sched: Fix UP update_avg() build warning make mrproper && cp ../Hikaruconfig .config && XZ_OPT="" CCACHE_DISABLE="1" time make oldconfig bzImage modules 5669.54user 528.39system 1:51:11elapsed 92%CPU (0avgtext+0avgdata 738000maxresident)k 550632inputs+1991400outputs (335major+106506270minor)pagefaults 0swaps make mrproper && XZ_OPT="" CCACHE_DISABLE="1" time make allnoconfig 5.44user 0.52system 0:06.32elapsed 94%CPU (0avgtext+0avgdata 95888maxresident)k 0inputs+1920outputs (0major+126547minor)pagefaults 0swaps As you can see there is VERY little difference between the two compile times. I wasn't expecting this - either I myself made an error when I did my previous test compiles, there is a different bug lurking in 2.6.35.6 that I happened to trigger at the same time, or the loadaverage bug is inconsistently impacting performance. I really don't know; I will do allnoconfig compile tests vs 2.6.25 and 2.6.25.6 as time permits and reply to this thread. (I'll have to regenerate these kernels from scratch) However it's obvious at this time that this specific commit I've singled out from this tests results only appears to impact the loadaverage statistic and may in fact not be causing a performance problem as I'd led myself to believe. Tim McGrath --zYM0uCDKw75PZbzx Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iQEVAwUBTKWuXpEncCrqzVruAQKcRAgAkL5EhC8xjFX89s10ljZWAgsfF/uwf1iK 1VLppumX0Az02TLfehhYDuVhg90NJs/hMOpYZ5cFsSrNhGDGs1w/nSF+Z0VJFA0L KjlZIbRcNqiN7FVhBYHOFQUi1Esdrk4OoY62wfvl1vvzFmfWwkx2srS/HAJDd1uL x0p5NpWA6WYpL84KmzRfZQAeUYGrGLAZvy1DXsFmMDv75Si3pC5dy4nm9wmEGEeZ +Csal3LVa2r68zx9W+gHPYSu/McQwy+JCYre+DQS4PQMwISVO4JRR4PJWf4m+M1w qjzFtobLM0lpCZOkX2EUbgJ0OXkQAYNpaCfU+b5CTnYC+QZwDPdwog== =L1PI -----END PGP SIGNATURE----- --zYM0uCDKw75PZbzx--