linux-kernel - Re: [PATCH 2/2] x86: replace BIO_VMERGE_BOUNDARY with BIOVEC_PHYS

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Message-ID: <20081029083713.GE6364@elte.hu>
Date:	Wed, 29 Oct 2008 09:37:13 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Cc:	jens.axboe@...cle.com, jeremy@...p.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86: replace BIO_VMERGE_BOUNDARY with
	BIOVEC_PHYS_MERGEABLE


* FUJITA Tomonori <fujita.tomonori@....ntt.co.jp> wrote:

> On Mon, 27 Oct 2008 12:57:00 +0100
> Jens Axboe <jens.axboe@...cle.com> wrote:
> 
> > On Mon, Oct 27 2008, Jeremy Fitzhardinge wrote:
> > > Jens Axboe wrote:
> > > >Pretty much baffles me as well, xen should just need to do
> > > >
> > > >#define BIOVEC_PHYS_MERGEABLE(vec1, vec2)       0
> > > >  
> > > 
> > > It needs to be a runtime switch, since we only want to do this when 
> > > actually running under Xen.  Also, its possible that the two pages might 
> > > actually be physically contiguous, so they could be merged anyway.
> > 
> > Alright, then add a xen_biovec_phys_mergeable(vec1, vec2) in the xen
> > code that actually checks this for real. You can add your switch there
> > as well. Then put the BIOVEC_PHYS_MERGEABLE() in the xen arch includes,
> > done.
> > 
> > What Tomo is saying is that this has nothing to do with virtual merging,
> > and he's right.
> 
> Yeah, overriding BIOVEC_PHYS_MERGEABLE perfectly works for Xen. And it
> is not related with BIO_VMERGE_BOUNDARY at all.
> 
> Ingo, please put this patch into your tree:
> 
> http://marc.info/?l=linux-kernel&m=122482703716620&w=2

does it have any dependency on:

  Subject: [PATCH 1/2] bio: define __BIOVEC_PHYS_MERGEABLE

?

	Ingo
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