linux-kernel - Re: [PATCH 08 of 11] anon-vma-rwsem

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Date:	Wed, 7 May 2008 23:26:50 +0200
From:	Andrea Arcangeli <andrea@...ranet.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <clameter@....com>,
	Jack Steiner <steiner@....com>, Robin Holt <holt@....com>,
	Nick Piggin <npiggin@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	kvm-devel@...ts.sourceforge.net,
	Kanoj Sarcar <kanojsarcar@...oo.com>,
	Roland Dreier <rdreier@...co.com>,
	Steve Wise <swise@...ngridcomputing.com>,
	linux-kernel@...r.kernel.org, Avi Kivity <avi@...ranet.com>,
	linux-mm@...ck.org, general@...ts.openfabrics.org,
	Hugh Dickins <hugh@...itas.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Anthony Liguori <aliguori@...ibm.com>,
	Chris Wright <chrisw@...hat.com>,
	Marcelo Tosatti <marcelo@...ck.org>,
	Eric Dumazet <dada1@...mosbay.com>,
	"Paul E. McKenney" <paulmck@...ibm.com>
Subject: Re: [PATCH 08 of 11] anon-vma-rwsem

On Wed, May 07, 2008 at 01:56:23PM -0700, Linus Torvalds wrote:
> This also looks very debatable indeed. The only performance numbers quoted 
> are:
> 
> >   This results in f.e. the Aim9 brk performance test to got down by 10-15%.
> 
> which just seems like a total disaster.
> 
> The whole series looks bad, in fact. Lack of authorship, bad single-line 

Glad you agree. Note that the fact the whole series looks bad, is
_exactly_ why I couldn't let Christoph keep going with
mmu-notifier-core at the very end of his patchset. I had to move it at
the top to have a chance to get the KVM and GRU requirements merged
in 2.6.26.

I think the spinlock->rwsem conversion is ok under config option, as
you can see I complained myself to various of those patches and I'll
take care they're in a mergeable state the moment I submit them. What
XPMEM requires are different semantics for the methods, and we never
had to do any blocking I/O during vmtruncate before, now we have to.
And I don't see a problem in making the conversion from
spinlock->rwsem only if CONFIG_XPMEM=y as I doubt XPMEM works on
anything but ia64.

Please ignore all patches but mmu-notifier-core. I regularly forward
_only_ mmu-notifier-core to Andrew, that's the only one that is in
merge-ready status, everything else is just so XPMEM can test and we
can keep discussing it to bring it in a mergeable state like
mmu-notifier-core already is.
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