Re: [Xen-devel] Re: [rfc] [patch] grant_entry.flags accessors

[Hollis Blanchard <hollisb@xxxxxxxxxx>]

On Wed, 2006-06-28 at 07:43 +0100, Keir Fraser wrote:
> On 27 Jun 2006, at 18:45, Jimi Xenidis wrote:
> 
> > Hmm, the interesting part is that as far as bit-ops go in Linux x86 
> > converged to longs rather then ppc converging to some the arbitrary 
> > bit method:
> > see:
> >   include/asm-i386/bitops.h clear_bit 71 static inline void 
> > clear_bit(int nr, volatile unsigned long * addr)
> >
> > I've been told this was to solve a performance issue, but I am no 
> > expert.
> 
> Well there would be a performance impact for other architectures, no 
> doubt. x86/64 never moved to longs for bitops.

They wouldn't have to. Because other architectures did, especially i386,
that ensures that all common code will use bitops only on longs, which
is what we'd like to see in Xen as well.

-- 
Hollis Blanchard
IBM Linux Technology Center


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