Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934556AbXEHHvv (ORCPT ); Tue, 8 May 2007 03:51:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934501AbXEHHvr (ORCPT ); Tue, 8 May 2007 03:51:47 -0400 Received: from mail.gmx.net ([213.165.64.20]:60157 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S934484AbXEHHvq (ORCPT ); Tue, 8 May 2007 03:51:46 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1+PPvMxLw+P9l60wpXykLyP8P7FJqQ020rf2QkTIq DaqX66Btm8mSoR Subject: Re: [patch] CFS scheduler, -v10 From: Mike Galbraith To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Andrew Morton , Con Kolivas , Nick Piggin , Arjan van de Ven , Peter Williams , Thomas Gleixner , caglar@pardus.org.tr, Willy Tarreau , Gene Heskett , Mark Lord In-Reply-To: <20070507163342.GA3502@elte.hu> References: <20070507163342.GA3502@elte.hu> Content-Type: text/plain Date: Tue, 08 May 2007 09:51:38 +0200 Message-Id: <1178610698.7558.48.camel@Homer.simpson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.8.2 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1858 Lines: 48 On Mon, 2007-05-07 at 18:33 +0200, Ingo Molnar wrote: > - complete and finetune the 'smooth load calculation' mechanism > (Mike Galbraith) Houston, we have alien artifacts. Artifact 1: root@Homer: taskset -c 1 ./thud 5 starting 5 children running... root@Homer: taskset -c 1 ./chew pid 7551, prio 0, interval of 99984800 nsec pid 7551, prio 0, out for 7 ms, ran for 1690 ms, load 99% pid 7551, prio 0, out for 2 ms, ran for 1794 ms, load 99% pid 7551, prio 0, out for 4 ms, ran for 9665 ms, load 99% pid 7551, prio 0, out for 775 ms, ran for 379 ms, load 32% <== hurt pain ouch! pid 7551, prio 0, out for 32 ms, ran for 6 ms, load 17% pid 7551, prio 0, out for 32 ms, ran for 4 ms, load 13% pid 7551, prio 0, out for 32 ms, ran for 4 ms, load 13% pid 7551, prio 0, out for 32 ms, ran for 4 ms, load 13% When thud starts, chew takes a size 14EEE latency hit if bits 1, 2 and 3 are set in sysctl_sched_load_smoothing. Good for burst load, rotten for interactivity if that burst load ain't X. Start a thud 5 without the taskset, and you'll feel the lurch. Artifact 2: If both bits 1 and 2 are set, and bit 3 is _not_ set, chew's out drops to ~6ms and run drops to < 1ms. Excessive context switching. Computing delta_fair with smoothed load in update_curr() fixes some things, but still breaks others. The cost/benefit ratio isn't adding up very favorably. Tinkering. Values 0x7 and 0xf should be avoided the like plague if your test load includes bursty multiple hogs-from-hell. Values 0x3 and 0xb are merely context switch happy. -Mike - 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/