From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f173.google.com (mail-wi0-f173.google.com [209.85.212.173]) by kanga.kvack.org (Postfix) with ESMTP id E53A66B0031 for ; Mon, 7 Apr 2014 11:49:41 -0400 (EDT) Received: by mail-wi0-f173.google.com with SMTP id z2so5358775wiv.0 for ; Mon, 07 Apr 2014 08:49:41 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id vj2si6395842wjc.184.2014.04.07.08.49.39 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 07 Apr 2014 08:49:40 -0700 (PDT) Date: Mon, 7 Apr 2014 16:49:35 +0100 From: Mel Gorman 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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, 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