Re: [Qemu-devel] [PATCH 02/10] compiler.h: add QEMU_CACHELINE + QEMU_ALIGN() + QEMU_CACHELINE_ALIGNED

["Emilio G. Cota" <cota@braap.org>]

On Tue, Apr 05, 2016 at 19:01:07 +0100, Peter Maydell wrote:
> On 5 April 2016 at 18:24, Emilio G. Cota <cota@braap.org> wrote:
> > So how about this:
> > we add these defaults, and also add an optional --configure
> > parameter to override said defaults.
> 
> I think this definitely doesn't merit a configure parameter.

Agreed :)

> > Otherwise I'd just stick to 64.
> 
> If this is basically just a hashtable semi-tunable parameter knob,
> then I don't mind if we use 64 everywhere (or some slightly more
> architecture-aware default). But I would prefer that we not make
> it a global define QEMU_CACHELINE if we can't actually guarantee
> that it's the size of the cacheline (which we can't), because I
> think that will be confusing and invite future misuse.
> 
> Unless we have another use case in the tree at the moment for
> a number which is "probably the cacheline size, but might be
> smaller or larger if you're unlucky", in which case we just want
> a better name :-)

Ok, so for now I'll only leave the ALIGN() macro, and then use
ALIGN(64) in the hash table. We can always reconsider adding a
more proper definition if this gets widespread use.

Thanks,

		Emilio