From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752077AbXG1MhJ (ORCPT ); Sat, 28 Jul 2007 08:37:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750783AbXG1Mg4 (ORCPT ); Sat, 28 Jul 2007 08:36:56 -0400 Received: from wa-out-1112.google.com ([209.85.146.183]:8843 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750731AbXG1Mgz (ORCPT ); Sat, 28 Jul 2007 08:36:55 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=jDXPK5+IQUkWYNV+uyPYYg41TsPUnl08nr4oljtJf+YRmewoJfbKz0coQhS1BAoKqYw0XeMgE7AXlBJJD7/RkWviYrG0qXbvgoe5rC9u8IaWXBKQSyNJ78ljUN6fX37KCjyJcM3jlzelDYTnC4Douw1xAkOnaRwM8CMIlAxPvxs= Message-ID: Date: Sat, 28 Jul 2007 14:36:54 +0200 From: "Dmitry Adamushko" To: tim.c.chen@linux.intel.com Subject: Re: Volanomark slows by 80% under CFS Cc: "Ingo Molnar" , "Linux Kernel" In-Reply-To: <1185573687.19777.44.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <1185573687.19777.44.camel@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 28/07/07, Tim Chen wrote: > [ ... ] > It may make sense to queue the > yielding process a bit further behind in the queue. > I made a slight change by zeroing out wait_runtime > (i.e. have the process gives > up cpu time due for it to run) for experimentation. But that's wrong. The 'wait_runtime' might have been negative at this point (i.e. a task is in the negative 'run-time' balance wrt the 'etalon' nice-0 task). Your change ends up helping such a task to actually stay closer to the 'left most' element of the tree (or to be it) and not "further behind in the queue" as your intention is. I don't know Volanomark's details so refrain from speculating on why this change "improves" benchmark results indeed (maybe some afected tasks have positive 'wait_runtime's on average for this setup). If you want to make sure (just for a test) a yeilding task is not the left-most (at least) for some short interval of time (likely to be <= 1 tick), take a look at yield_task_fair() in e.g. cfs-v15. > Volanomark runs better > and is only 40% (instead of 80%) down from old scheduler > without CFS. 40 or 80 % is still a huge regression. > > Regards, > Tim > -- Best regards, Dmitry Adamushko