Re: [Xen-devel] [PATCH RFC] x86: slightly reduce RSB overwrite overhead

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.02.18 at 12:09, <JBeulich@xxxxxxxx> wrote:
> Avoiding the PAUSE/LFENCE pair on the first of the two unrolled
> iterations not only reduces code size, but also improves performance
> according to my (limited) measurements (by 15-20 cycles on my Westmere;
> granted I can't really explain why that is). Now that the two iterations
> are sufficiently different, remove the use of .irp; otherwise .if would
> need to be added to its body.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> RFC because this presumably wants verification on other CPU models.

I'm withdrawing this patch - I've just checked and it makes things
worse on Sandybridge.

Jan


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