From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754110Ab2KGKir (ORCPT ); Wed, 7 Nov 2012 05:38:47 -0500 Received: from cantor2.suse.de ([195.135.220.15]:58542 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751300Ab2KGKip (ORCPT ); Wed, 7 Nov 2012 05:38:45 -0500 Date: Wed, 7 Nov 2012 10:38:39 +0000 From: Mel Gorman To: Rik van Riel Cc: Peter Zijlstra , Andrea Arcangeli , Ingo Molnar , Johannes Weiner , Hugh Dickins , Thomas Gleixner , Linus Torvalds , Andrew Morton , Linux-MM , LKML Subject: Re: [PATCH 08/19] mm: numa: Create basic numa page hinting infrastructure Message-ID: <20121107103839.GT8218@suse.de> References: <1352193295-26815-1-git-send-email-mgorman@suse.de> <1352193295-26815-9-git-send-email-mgorman@suse.de> <50995DD2.8000200@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <50995DD2.8000200@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 06, 2012 at 01:58:26PM -0500, Rik van Riel wrote: > On 11/06/2012 04:14 AM, Mel Gorman wrote: > >Note: This patch started as "mm/mpol: Create special PROT_NONE > > infrastructure" and preserves the basic idea but steals *very* > > heavily from "autonuma: numa hinting page faults entry points" for > > the actual fault handlers without the migration parts. The end > > result is barely recognisable as either patch so all Signed-off > > and Reviewed-bys are dropped. If Peter, Ingo and Andrea are ok with > > this version, I will re-add the signed-offs-by to reflect the history. > > > >In order to facilitate a lazy -- fault driven -- migration of pages, create > >a special transient PAGE_NUMA variant, we can then use the 'spurious' > >protection faults to drive our migrations from. > > > >Pages that already had an effective PROT_NONE mapping will not be detected > > The patch itself is good, but the changelog needs a little > fix. While you are defining _PAGE_NUMA to _PAGE_PROTNONE on > x86, this may be different on other architectures. > > Therefore, the changelog should refer to PAGE_NUMA, not > PROT_NONE. > Fair point. I still want to record the point that PROT_NONE will not generate the faults though. How about this? In order to facilitate a lazy -- fault driven -- migration of pages, create a special transient PAGE_NUMA variant, we can then use the 'spurious' protection faults to drive our migrations from. The meaning of PAGE_NUMA depends on the architecture but on x86 it is effectively PROT_NONE. In this case, PROT_NONE mappings will not be detected to generate these 'spurious' faults for the simple reason that we cannot distinguish them on their protection bits, see pte_numa(). This isn't a problem since PROT_NONE (and possible PROT_WRITE with dirty tracking) aren't used or are rare enough for us to not care about their placement. > >to generate these 'spurious' faults for the simple reason that we cannot > >distinguish them on their protection bits, see pte_numa(). This isn't > >a problem since PROT_NONE (and possible PROT_WRITE with dirty tracking) > >aren't used or are rare enough for us to not care about their placement. > > > >Signed-off-by: Mel Gorman > > Other than the changelog ... > > Reviewed-by: Rik van Riel Thanks. -- Mel Gorman SUSE Labs