Re: [PATCH 2/2] x86: replace BIO_VMERGE_BOUNDARY with BIOVEC_PHYS_MERGEABLE

[Jeremy Fitzhardinge]

Ingo Molnar wrote:
> * FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> wrote:
>
>   
> > On Mon, 27 Oct 2008 12:57:00 +0100
> > Jens Axboe <jens.axboe@xxxxxxxxxx> 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
>   

No, they're independent.  Defining __BIOVEC_PHYS_MERGEABLE will be 
useful for the Xen changes I need to make in the wake of Tomo's patch.

   J
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