Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755718AbaDGTQ0 (ORCPT ); Mon, 7 Apr 2014 15:16:26 -0400 Received: from mail-lb0-f180.google.com ([209.85.217.180]:45544 "EHLO mail-lb0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755610AbaDGTQZ (ORCPT ); Mon, 7 Apr 2014 15:16:25 -0400 Date: Mon, 7 Apr 2014 23:16:22 +0400 From: Cyrill Gorcunov 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 Subject: Re: [PATCH 2/3] x86: Define _PAGE_NUMA with unused physical address bits PMD and PTE levels Message-ID: <20140407191622.GA23983@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> <20140407161910.GJ1444@moon> <20140407182854.GH7292@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140407182854.GH7292@suse.de> 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 07:28:54PM +0100, Mel Gorman wrote: > > > 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). > > I had considered the soft-dirty tracking usage of the same bit. I thought I'd > be able to swizzle around it or a further worst case of having soft-dirty and > automatic NUMA balancing mutually exclusive. Unfortunately upon examination > it's not obvious how to have both of them share a bit and I suspect any > attempt to will break CRIU. In my current tree, NUMA_BALANCING cannot be > set if MEM_SOFT_DIRTY which is not particularly satisfactory. Next on the > list is examining if _PAGE_BIT_IOMAP can be used. Thanks for info, Mel! It seems indeed if no more space left on x86-64 (in the very worst case which I still think won't happen anytime soon) we'll have to make them mut. exclusive. But for now (with 62 bit used for numa) they can live together, right? -- 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/