Date: Mon, 7 Apr 2014 23:36:46 +0400
From: Cyrill Gorcunov <gorcunov@gmail.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Mel Gorman <mgorman@suse.de>, David Vrabel <david.vrabel@citrix.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>, Steven Noonan <steven@uplinklabs.net>,
        Rik van Riel <riel@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrea Arcangeli <aarcange@redhat.com>, Linux-MM <linux-mm@kvack.org>,
        Linux-X86 <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Pavel Emelyanov <xemul@parallels.com>
Subject: Re: [PATCH 2/3] x86: Define _PAGE_NUMA with unused physical address
 bits PMD and PTE levels
Message-ID: <20140407193646.GC23983@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>
 <5342FC0E.9080701@zytor.com>
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On Mon, Apr 07, 2014 at 12:27:10PM -0700, H. Peter Anvin wrote:
> On 04/07/2014 11:28 AM, Mel Gorman wrote:
> > 
> > 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.
> 
> Didn't we smoke the last user of _PAGE_BIT_IOMAP?

Seems so, at least for non-kernel pages (not considering this bit references in
xen code, which i simply don't know but i guess it's used for kernel pages only).
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