Re: [Xen-devel] [PATCH] x86: introduce specialized clear_page()

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 20/6/07 16:35, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

>> I measure no benefit from the XMM version (nor from upgrading the SSE2
>> version on x86/64 to clear from %rax instead of %eax). I guess this is
>> because the move is non-temporal and it's actually quite easy to max the
>> memory bandwidth.
> 
> Neither did I, except (obviously) on machines having SSE, but not SSE2 (which
> was what I considered applying this for, with the additional need to tweak
> idle vcpu handling so that in that context [where FP context altering doesn't
> matter, as long as the rest of the system's aware of it] it could then be
> used).

Oh, yes. Well, that's not a very interesting set of CPUs to optimise for.

 -- Keir


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