RE: [Xen-ia64-devel] CONFIG_DOMAIN0_CONTIGUOUS in domain.c

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

This isn't a performance issue.  I don't think domain0/U
will function correctly with CONFIG_...CONTIGUOUS undef'd
until all of Isaku's necessary VP+DMA changes (in Xen,
Xenlinux, Xen drivers, and possibly tools) are complete.

> -----Original Message-----
> From: Dong, Eddie [mailto:eddie.dong@xxxxxxxxx] 
> Sent: Tuesday, February 28, 2006 4:19 PM
> To: Magenheimer, Dan (HP Labs Fort Collins); Tian, Kevin; 
> Isaku Yamahata
> Cc: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-ia64-devel] CONFIG_DOMAIN0_CONTIGUOUS in domain.c
> 
> Magenheimer, Dan (HP Labs Fort Collins) wrote:
> > to VP.  HOWEVER... it may be possible and desirable
> > for much of Isaku's work to support both VP and P==M.
> > For non-I/O code, CONFIG_DOMAIN0_CONTIGUOUS could be
> > used (or possibly renamed) to select VP or P==M at
> > compile-time, at least until the conversion to VP+DMA
> > is complete.  This would allow at least some of Isaku's
> As if eventually we will remove this code, putting an compile 
> option now is OK IMO. But I think the default one should be 
> #undefed by some pre-cleanip patch now so that people can 
> find issues earlier if there have. 
> #undef this one can support no matter p==m or p!=m, while 
> #define this can only support p==m. Yes maybe we will see 
> 0.5% performance degradation with #undef, but this is a 
> functionality must as we all go toward p!=m :-(
> After the whole p2m/VP patch comes out, we can then do more 
> performance tuning :-)
> Eddie
> 

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