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Date: Thu, 24 Apr 2008 00:05:45 +0300
From: Avi Kivity <avi@qumranet.com>
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To: Robin Holt <holt@sgi.com>
CC: Andrea Arcangeli <andrea@qumranet.com>,
       Christoph Lameter <clameter@sgi.com>, Nick Piggin <npiggin@suse.de>,
       Jack Steiner <steiner@sgi.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
       kvm-devel@lists.sourceforge.net, Kanoj Sarcar <kanojsarcar@yahoo.com>,
       Roland Dreier <rdreier@cisco.com>,
       Steve Wise <swise@opengridcomputing.com>, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org, general@lists.openfabrics.org,
       Hugh Dickins <hugh@veritas.com>, akpm@linux-foundation.org,
       Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [PATCH 04 of 12] Moves all mmu notifier methods outside the PT
 lock (first and not last
References: <ac9bb1fb3de2aa5d2721.1208872280@duo.random> <Pine.LNX.4.64.0804221323510.3640@schroedinger.engr.sgi.com> <20080422224048.GR24536@duo.random> <Pine.LNX.4.64.0804221613570.4868@schroedinger.engr.sgi.com> <20080423134427.GW24536@duo.random> <20080423154536.GV30298@sgi.com>
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Robin Holt wrote:
>> an hurry like we are, we can't progress without this. Infact we can
>>     
>
> SGI is under an equally strict timeline.  We really needed the sleeping
> version into 2.6.26.  We may still be able to get this accepted by
> vendor distros if we make 2.6.27.
>   

The difference is that the non-sleeping variant can be shown not to 
affect stability or performance, even if configed in, as long as its not 
used.  The sleeping variant will raise performance and stability concerns.

I have zero objections to sleeping mmu notifiers; I only object to tying 
the schedules of the two together.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.