From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-la0-f47.google.com (mail-la0-f47.google.com [209.85.215.47]) by kanga.kvack.org (Postfix) with ESMTP id 07BA96B0031 for ; Mon, 7 Apr 2014 12:19:14 -0400 (EDT) Received: by mail-la0-f47.google.com with SMTP id pn19so4914619lab.6 for ; Mon, 07 Apr 2014 09:19:13 -0700 (PDT) Received: from mail-la0-x22a.google.com (mail-la0-x22a.google.com [2a00:1450:4010:c03::22a]) by mx.google.com with ESMTPS id y6si12662332lal.131.2014.04.07.09.19.11 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 07 Apr 2014 09:19:12 -0700 (PDT) Received: by mail-la0-f42.google.com with SMTP id ec20so5090279lab.1 for ; Mon, 07 Apr 2014 09:19:11 -0700 (PDT) Date: Mon, 7 Apr 2014 20:19:10 +0400 From: Cyrill Gorcunov Subject: Re: [PATCH 2/3] x86: Define _PAGE_NUMA with unused physical address bits PMD and PTE levels Message-ID: <20140407161910.GJ1444@moon> References: <1396883443-11696-1-git-send-email-mgorman@suse.de> <1396883443-11696-3-git-send-email-mgorman@suse.de> <5342C517.2020305@citrix.com> <20140407154935.GD7292@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140407154935.GD7292@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: David Vrabel , Linus Torvalds , Peter Anvin , Ingo Molnar , Steven Noonan , Rik van Riel , Andrew Morton , Peter Zijlstra , Andrea Arcangeli , Linux-MM , Linux-X86 , LKML , Pavel Emelyanov On Mon, Apr 07, 2014 at 04:49:35PM +0100, Mel Gorman wrote: > 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. Fwiw, we're using bit 11 for soft-dirty tracking, so i really hope worst case never happen. (At the moment I'm trying to figure out if with this set it would be possible to clean up ugly macros in pgoff_to_pte for 2 level pages). -- 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