Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754586AbaDGPtn (ORCPT ); Mon, 7 Apr 2014 11:49:43 -0400 Received: from cantor2.suse.de ([195.135.220.15]:51914 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751946AbaDGPtl (ORCPT ); Mon, 7 Apr 2014 11:49:41 -0400 Date: Mon, 7 Apr 2014 16:49:35 +0100 From: Mel Gorman To: David Vrabel Cc: Linus Torvalds , Cyrill Gorcunov , Peter Anvin , Ingo Molnar , Steven Noonan , Rik van Riel , Andrew Morton , Peter Zijlstra , Andrea Arcangeli , Linux-MM , Linux-X86 , LKML Subject: Re: [PATCH 2/3] x86: Define _PAGE_NUMA with unused physical address bits PMD and PTE levels Message-ID: <20140407154935.GD7292@suse.de> References: <1396883443-11696-1-git-send-email-mgorman@suse.de> <1396883443-11696-3-git-send-email-mgorman@suse.de> <5342C517.2020305@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <5342C517.2020305@citrix.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 Mon, Apr 07, 2014 at 04:32:39PM +0100, David Vrabel wrote: > On 07/04/14 16:10, Mel Gorman wrote: > > _PAGE_NUMA is currently an alias of _PROT_PROTNONE to trap NUMA hinting > > faults. As the bit is shared care is taken that _PAGE_NUMA is only used in > > places where _PAGE_PROTNONE could not reach but this still causes problems > > on Xen and conceptually difficult. > > The problem with Xen guests occurred because mprotect() /was/ confusing > PROTNONE mappings with _PAGE_NUMA and clearing the non-existant NUMA hints. > I didn't bother spelling it out in case I gave the impression that I was blaming Xen for the problem. As the bit is now changes, does it help the Xen problem or cause another collision of some sort? There is no guarantee _PAGE_NUMA will remain as bit 62 but at worst it'll use bit 11 and NUMA_BALANCING will depend in !KMEMCHECK. -- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/