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Date: Tue, 5 Apr 2016 15:13:41 -0400
From: "Emilio G. Cota" <cota@braap.org>
Message-ID: <20160405191341.GA27828@flamenco>
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Subject: Re: [Qemu-devel] [PATCH 02/10] compiler.h: add QEMU_CACHELINE +
 QEMU_ALIGN() + QEMU_CACHELINE_ALIGNED
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: MTTCG Devel <mttcg@listserver.greensocs.com>, MTTCG Devel <mttcg@greensocs.com>, Peter Crosthwaite <crosthwaite.peter@gmail.com>, QEMU Developers <qemu-devel@nongnu.org>, Sergey Fedorov <serge.fdrv@gmail.com>, Paolo Bonzini <pbonzini@redhat.com>, Alex =?iso-8859-1?Q?Benn=E9e?= <alex.bennee@linaro.org>, Richard Henderson <rth@twiddle.net>

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