From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758110Ab2EYR4N (ORCPT ); Fri, 25 May 2012 13:56:13 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:35581 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754124Ab2EYR4L (ORCPT ); Fri, 25 May 2012 13:56:11 -0400 Date: Fri, 25 May 2012 10:55:44 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: Peter Zijlstra , Dario Faggioli , Colin Cross , linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner , Hillf Danton Subject: Re: [PATCH] sched/rt: fix SCHED_RR across cgroups Message-ID: <20120525175544.GF2396@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1337229266-15798-1-git-send-email-ccross@android.com> <1337331395.573.3.camel@twins> <1337366237.573.106.camel@twins> <1337433062.7075.9.camel@Abyss> <1337779944.27368.94.camel@Solace> <1337946769.9783.189.camel@laptop> <1337951526.13348.249.camel@gandalf.stny.rr.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1337951526.13348.249.camel@gandalf.stny.rr.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12052517-1780-0000-0000-000005E36B36 X-IBM-ISS-SpamDetectors: X-IBM-ISS-DetailInfo: BY=3.00000277; HX=3.00000188; KW=3.00000007; PH=3.00000001; SC=3.00000002; SDB=6.00142304; UDB=6.00032816; UTC=2012-05-25 17:56:10 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 25, 2012 at 09:12:06AM -0400, Steven Rostedt wrote: > On Fri, 2012-05-25 at 13:52 +0200, Peter Zijlstra wrote: > > On Wed, 2012-05-23 at 15:32 +0200, Dario Faggioli wrote: > > > Again, I really think it is the intended behaviour, and yes, real-time > > > group scheduling "breaks" the POSIX specification of the SCHED_{FIFO,RR} > > > policies intentionally (and _proudly_, as Peter would say it, am I > > > wrong? :-P). > > > > No, cgroups are well outside of POSIX ;-) as is SMP in fact. > > That's because the POSIX standards committee is still struggling to come > up with standardized SMP calls to handle NR_CPUS = 0 ;-) ;-) ;-) > Isn't Paul on that committee? ;-) I have met with them occasionally, but have spent most of my time on the C/C++ committees. I didn't try sounding them out on NR_CPUS=0, partly because they were choking pretty hard on NR_CPUS=4096. At least part of the problem is that every OS out there has different SMP feature, so the only way it would be possible to get this sort of thing through the committee would be to invent something that was roughly equally incompatible with everyone. However, there are some SMP features standardized by various random committees and aggregated by The Open Group, including: o The pthread_mutex_lock() API o pthread_getspecific() and pthread_setspecific() o pthread_getconcurrency() and pthread_setconcurrency() But yes, even the aggregated standard is quite limiting. Thanx, Paul