From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752181Ab1DGGl2 (ORCPT ); Thu, 7 Apr 2011 02:41:28 -0400 Received: from mga03.intel.com ([143.182.124.21]:14989 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751690Ab1DGGl1 (ORCPT ); Thu, 7 Apr 2011 02:41:27 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.63,315,1299484800"; d="scan'208";a="415228379" Subject: Re: [PATCH] sched: recover sched_yield task running time increase From: "Alex,Shi" To: Rik van Riel Cc: Peter Zijlstra , "linux-kernel@vger.kernel.org" , "mingo@elte.hu" , "Chen, Tim C" , "Li, Shaohua" In-Reply-To: <4D9D55EF.3090606@redhat.com> References: <1302042823-23022-1-git-send-email-alex.shi@intel.com> <1302077064.2225.1357.camel@twins> <1302145733.15889.7472.camel@debian> <4D9D55EF.3090606@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Thu, 07 Apr 2011 14:43:16 +0800 Message-ID: <1302158596.15889.7499.camel@debian> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2011-04-07 at 14:13 +0800, Rik van Riel wrote: > 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? I used openjdk from fedora 10~13 and jrockit-R27.3.1-jre1.5.0_11, both of them use sched_yield much. And I just did a quick try with jrockit-R27.4.0-jre1.6.0_02.x86_64, it had same problem. > > Surely not every JVM uses user space spinlocks and > yield, when we have futexes available? No, just 7 times futex called in testing, so I think the JVM did not use it. > > >