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

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Message-Id: <20081029080603J.fujita.tomonori@lab.ntt.co.jp>
Date:	Wed, 29 Oct 2008 08:06:09 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	jens.axboe@...cle.com
Cc:	jeremy@...p.org, fujita.tomonori@....ntt.co.jp,
	linux-kernel@...r.kernel.org, mingo@...e.hu
Subject: Re: [PATCH 2/2] x86: replace BIO_VMERGE_BOUNDARY with
 BIOVEC_PHYS_MERGEABLE

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


Thanks,
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