From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx193.postini.com [74.125.245.193]) by kanga.kvack.org (Postfix) with SMTP id F00966B005A for ; Fri, 19 Oct 2012 13:54:40 -0400 (EDT) Message-ID: <1350669236.2768.66.camel@twins> Subject: Re: question on NUMA page migration From: Peter Zijlstra Date: Fri, 19 Oct 2012 19:53:56 +0200 In-Reply-To: <50818A41.7030909@redhat.com> References: <5081777A.8050104@redhat.com> <1350664742.2768.40.camel@twins> <50818A41.7030909@redhat.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Rik van Riel Cc: Andrea Arcangeli , Ingo Molnar , Linux Memory Management List , Mel Gorman , Linux kernel Mailing List On Fri, 2012-10-19 at 13:13 -0400, Rik van Riel wrote: > Would it make sense to have the normal page migration code always > work with the extra refcount, so we do not have to introduce a new > MIGRATE_FAULT migration mode? >=20 > On the other hand, compaction does not take the extra reference... Right, it appears to not do this, it gets pages from the pfn and zone->lock and the isolate_lru_page() call is the first reference. > Another alternative might be to do the put_page inside > do_prot_none_numa(). That would be analogous to do_wp_page > disposing of the old page for the caller. It'd have to be inside migrate_misplaced_page(), can't do before isolate_lru_page() or the page might disappear. Doing it after is (obviously) too late. > I am not real happy about NUMA migration introducing its own > migration mode... You didn't seem to mind too much earlier, but I can remove it if you want. -- 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/ . Don't email: email@kvack.org