linux-kernel - Re: [PATCH] mmu notifiers #v7

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Message-ID: <Pine.LNX.4.64.0802281700060.1954@schroedinger.engr.sgi.com>
Date:	Thu, 28 Feb 2008 17:03:01 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Andrea Arcangeli <andrea@...ranet.com>
cc:	Jack Steiner <steiner@....com>, Nick Piggin <npiggin@...e.de>,
	akpm@...ux-foundation.org, Robin Holt <holt@....com>,
	Avi Kivity <avi@...ranet.com>, Izik Eidus <izike@...ranet.com>,
	kvm-devel@...ts.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	general@...ts.openfabrics.org,
	Steve Wise <swise@...ngridcomputing.com>,
	Roland Dreier <rdreier@...co.com>,
	Kanoj Sarcar <kanojsarcar@...oo.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com
Subject: Re: [PATCH] mmu notifiers #v7

On Fri, 29 Feb 2008, Andrea Arcangeli wrote:

> > Also re the _notify variants: The binding to pte_clear_flush_young etc 
> > will become a problem for notifiers that want to sleep because 
> > pte_clear_flush is usually called with the pte lock held. See f.e. 
> > try_to_unmap_one, page_mkclean_one etc.
> 
> Calling __free_page out of the PT lock is much bigger
> change. do_wp_page will require changes anyway when the sleepable
> notifiers are merged.

I thought you wanted to get rid of the sync via pte lock?
What changes to do_wp_page do you envision?

> > It would be better if the notifier calls could be moved outside of the 
> > pte lock.
> 
> The point is that it can't make a difference right now, and my
> objective was to avoid unnecessary source code duplication (later it
> will be necessary, right now it isn't). By the time you rework
> do_wp_page, removing _notify will be a very minor detail compared to
> the rest of the changes to do_wp_page IMHO. Expanding it now won't
> provide a real advantage later.

What is the trouble with the current do_wp_page modifications? There is 
no need for invalidate_page() there so far. invalidate_range() does the 
trick there.

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