linux-kernel - Re: [ofa-general] Re: [patch 5/6] mmu_notifier: Support for drivers with revers maps (f.e. for XPmem)

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Message-Id: <200802261952.42567.nickpiggin@yahoo.com.au>
Date:	Tue, 26 Feb 2008 19:52:41 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Gleb Natapov <glebn@...taire.com>
Cc:	Robin Holt <holt@....com>, steiner@....com,
	Andrea Arcangeli <andrea@...ranet.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, linux-mm@...ck.org,
	Izik Eidus <izike@...ranet.com>,
	Kanoj Sarcar <kanojsarcar@...oo.com>,
	Roland Dreier <rdreier@...co.com>,
	linux-kernel@...r.kernel.org, Avi Kivity <avi@...ranet.com>,
	kvm-devel@...ts.sourceforge.net, daniel.blueman@...drics.com,
	general@...ts.openfabrics.org, akpm@...ux-foundation.org,
	Christoph Lameter <clameter@....com>
Subject: Re: [ofa-general] Re: [patch 5/6] mmu_notifier: Support for drivers with revers maps (f.e. for XPmem)

On Tuesday 26 February 2008 18:21, Gleb Natapov wrote:
> On Tue, Feb 26, 2008 at 05:11:32PM +1100, Nick Piggin wrote:
> > > You are missing one point here.  The MPI specifications that have
> > > been out there for decades do not require the process use a library
> > > for allocating the buffer.  I realize that is a horrible shortcoming,
> > > but that is the world we live in.  Even if we could change that spec,
> >
> > Can you change the spec?
>
> Not really. It will break all existing codes.

I meant as in eg. submit changes to MPI-3


> MPI-2 provides a call for 
> memory allocation (and it's beneficial to use this call for some
> interconnects), but many (most?) applications are still written for MPI-1
> and those that are written for MPI-2 mostly uses the old habit of
> allocating memory by malloc(), or even use stack or BSS memory for
> communication buffer purposes.

OK, so MPI-2 already has some way to do that... I'm not saying that we
can now completely dismiss the idea of using notifiers for this, but it
is just a good data point to know.

Thanks,
Nick

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