Re: [Xen-devel] My turn to rant about types... bitops

[Jimi Xenidis <jimix@xxxxxxxxxxxxxx>]

Always the job of the maintainer to ask why :)
Well, since linux bitops use unsigned long, being the largest machine  
word and therefore the most efficient, we get alignment issues.
The next request is really the jist of what we are after, doing 64bit  
operations 32bit aligned data kills us performance wise and WRT  
bitops cannot be used for atomic ops. If htis was just Xen I'd  
consider adding 32bit bitops but I doubt I'd be able to do that in  
Linux which does not provide "u32" bitops.
IIRC assuring this alignement would even help x86, no?
-JX

On Oct 5, 2005, at 2:17 PM, Keir Fraser wrote:


> On 5 Oct 2005, at 17:52, Jimi Xenidis wrote:
>
>
>
> > I think around linux-2.4.19 (and thanks to rusty?) bitops.h went s/ 
> > void */unsigned long */, any chance is Xen following suit?
> > The next request would be to change all arrays destined for bitops  
> > to be defined using unsigned long.
> > specifically:
> Just cast to 'unsigned long *' when you use those ops. Why work  
> around details of the way that Linux happens to do atomic ops in  
> our interfaces?
>  -- Keir
-JX
--
"I got an idea, an idea so smart my head would explode if I even
  began to know what I was talking about." -- Peter Griffin (Family  
Guy)




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