From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f177.google.com (mail-lb0-f177.google.com [209.85.217.177]) by kanga.kvack.org (Postfix) with ESMTP id 852166B006E for ; Mon, 7 Apr 2014 15:16:26 -0400 (EDT) Received: by mail-lb0-f177.google.com with SMTP id z11so5112824lbi.22 for ; Mon, 07 Apr 2014 12:16:25 -0700 (PDT) Received: from mail-lb0-x22f.google.com (mail-lb0-x22f.google.com [2a00:1450:4010:c04::22f]) by mx.google.com with ESMTPS id u5si12983825laa.52.2014.04.07.12.16.23 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 07 Apr 2014 12:16:24 -0700 (PDT) Received: by mail-lb0-f175.google.com with SMTP id w7so5187134lbi.34 for ; Mon, 07 Apr 2014 12:16:23 -0700 (PDT) Date: Mon, 7 Apr 2014 23:16:22 +0400 From: Cyrill Gorcunov 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> 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 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, 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