From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx204.postini.com [74.125.245.204]) by kanga.kvack.org (Postfix) with SMTP id E47716B004A for ; Mon, 19 Mar 2012 11:16:46 -0400 (EDT) Date: Mon, 19 Mar 2012 10:16:41 -0500 (CDT) From: Christoph Lameter Subject: Re: [RFC][PATCH 10/26] mm, mpol: Make mempolicy home-node aware In-Reply-To: <1332165959.18960.340.camel@twins> Message-ID: References: <20120316144028.036474157@chello.nl> <20120316144240.763518310@chello.nl> <1331932375.18960.237.camel@twins> <1332165959.18960.340.camel@twins> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: Linus Torvalds , Andrew Morton , Thomas Gleixner , Ingo Molnar , Paul Turner , Suresh Siddha , Mike Galbraith , "Paul E. McKenney" , Lai Jiangshan , Dan Smith , Bharata B Rao , Lee Schermerhorn , Andrea Arcangeli , Rik van Riel , Johannes Weiner , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Mon, 19 Mar 2012, Peter Zijlstra wrote: > > A HOME_NODE policy would also help to ensure that existing applications > > continue to work as expected. Given that people in the HPC industry and > > elsewhere have been fine tuning around the scheduler for years this is a > > desirable goal and ensures backward compatibility. > > I really have no idea what you're saying. Existing applications that use > mbind/set_mempolicy already continue to function exactly like before, > see how the new layer is below all that. No they wont work the same way as before. Applications may be relying on MPOL_DEFAULT behavior now expecting node local allocations. The home-node functionality would cause a difference in behavior because it would perform remote node allocs when a thread has been moved to a different socket. The changes also cause migrations that may cause additional latencies as well as change the location of memory in surprising ways for the applications -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org