Date: Wed, 27 Feb 2008 16:08:07 -0800 (PST)
From: Christoph Lameter <clameter@sgi.com>
To: Andrea Arcangeli <andrea@qumranet.com>
cc: Nick Piggin <npiggin@suse.de>, Steve Wise <swise@opengridcomputing.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-mm@kvack.org,
       Kanoj Sarcar <kanojsarcar@yahoo.com>, Roland Dreier <rdreier@cisco.com>,
       Jack Steiner <steiner@sgi.com>, linux-kernel@vger.kernel.org,
       Avi Kivity <avi@qumranet.com>, kvm-devel@lists.sourceforge.net,
       daniel.blueman@quadrics.com, Robin Holt <holt@sgi.com>,
       general@lists.openfabrics.org, akpm@linux-foundation.org
Subject: Re: [kvm-devel] [PATCH] mmu notifiers #v7
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On Thu, 28 Feb 2008, Andrea Arcangeli wrote:

> If RDMA/IB folks needed to block in invalidate_range, I guess they
> need to do so on top of tmpfs too, and that never worked with your
> patch anyway.

How about blocking in invalidate_page()? It can be made to work...

> > Would it not be better to have a solution that fits all instead of hacking 
> > something in now and then having to modify it later?
> 
> The whole point is that your solution fits only GRU and KVM too.

Well so we do not address the issues?
 
> XPMEM in your patch works in a hacked mode limited to anonymous memory
> only, Robin already received incoming mail asking to allow xpmem to
> work on more than anonymous memory, so your solution-that-fits-all
> doesn't actually fit some of Robin's customer needs. So if it doesn't
> even entirely satisfy xpmem users, imagine the other potential
> blocking-users of this code.

The solutions have been mentioned...

> anon_vma lock can remain a spinlock unless you also want to schedule
> inside try_to_unmap.

Either that or a separate rmap as also mentioned before.


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