From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753716AbXJ0Ihc (ORCPT ); Sat, 27 Oct 2007 04:37:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752051AbXJ0IhG (ORCPT ); Sat, 27 Oct 2007 04:37:06 -0400 Received: from netops-testserver-4-out.sgi.com ([192.48.171.29]:47720 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751639AbXJ0IhA (ORCPT ); Sat, 27 Oct 2007 04:37:00 -0400 Date: Sat, 27 Oct 2007 01:36:56 -0700 From: Paul Jackson To: Christoph Lameter Cc: rientjes@google.com, Lee.Schermerhorn@hp.com, akpm@linux-foundation.org, ak@suse.de, linux-kernel@vger.kernel.org Subject: Re: [patch 2/2] cpusets: add interleave_over_allowed option Message-Id: <20071027013656.4ffadb87.pj@sgi.com> In-Reply-To: References: <20071025185506.8c373aa8.pj@sgi.com> <1193412644.5032.13.camel@localhost> <20071026120037.7b95a136.pj@sgi.com> <1193433239.5032.95.camel@localhost> <1193434278.5032.106.camel@localhost> <20071026180713.aeedfac2.pj@sgi.com> <20071026194144.6042316a.pj@sgi.com> <20071026221624.cec512da.pj@sgi.com> Organization: SGI X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.3; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > Are you saying: > > 1) The kernel continues to default to Choice A, unless > > the flag enables Choice B, or > > 2) The kernel defaults to the new Choice B, unless the > > flag reverts to the old Choice A? > > If 2) is keeping the API semantics then 2. No .. (1) keeps the same API semantics. > Let everything be as it is today unless > numactl sets the new. > ... > Tough. The API needs to remain stable. Good - that I understand. Your position is clear now. You have chosen (1) above, which keeps Choice A as the default. Before I leave this part, there is one more thing I kinda really need, if you could, Christoph. Could you describe in your own words what you think Choices A and B mean? We seem to be having trouble communicating, and hence there is some risk right now that we don't mean the same thing by this new "Choice B". === Now ... onto the matter of permanent API warts: > > I wonder if there might be some way to avoid that permanent ugly wart > > on each and every set/get mempolicy system call forever afterward. > > Hmmm.. The alternative is to add new set/get mempolicy functions. Other alternatives include a per-system, per-cpuset or per-process flag, in addition to the per-system call flag you suggested earlier (MPOL_MF_RELATIVE), or whatever you mean by "new set/get mempolicy functions" ... could you elaborate on that one? So ... the question becomes this: How do we migrate to Choice B, without leaving both Choices permanently supported, and an ugly mode flag selecting the non-default Choice, while not breaking API's too abruptly? Thanks. -- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson 1.925.600.0401