From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752092Ab1DGGJz (ORCPT ); Thu, 7 Apr 2011 02:09:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40284 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751575Ab1DGGJy (ORCPT ); Thu, 7 Apr 2011 02:09:54 -0400 Message-ID: <4D9D55EF.3090606@redhat.com> Date: Thu, 07 Apr 2011 02:13:03 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101209 Fedora/3.1.7-0.35.b3pre.fc14 Lightning/1.0b3pre Thunderbird/3.1.7 MIME-Version: 1.0 To: "Alex,Shi" CC: Peter Zijlstra , "linux-kernel@vger.kernel.org" , "mingo@elte.hu" , "Chen, Tim C" , "Li, Shaohua" Subject: Re: [PATCH] sched: recover sched_yield task running time increase References: <1302042823-23022-1-git-send-email-alex.shi@intel.com> <1302077064.2225.1357.camel@twins> <1302145733.15889.7472.camel@debian> In-Reply-To: <1302145733.15889.7472.camel@debian> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/06/2011 11:08 PM, Alex,Shi wrote: > On Wed, 2011-04-06 at 16:04 +0800, Peter Zijlstra wrote: >> On Wed, 2011-04-06 at 06:33 +0800, Alex Shi wrote: >> You do know that any app that relies on sched_yield behaviour is more >> than broken? Using sched_yield() for anything other than SCHED_FIFO >> tasks is well outside spec. >> >> Furthermore, apparently you used sysctl_sched_compat_yield, which was >> bound to disappear some time, since with the default settings the yield >> semantics didn't actually change. > > Yes, I used sched_compat_yield, otherwise volano will become extremely > slow in my single machine testing. We may reconsider our testing > setting. With what JVM is this happening? Surely not every JVM uses user space spinlocks and yield, when we have futexes available?