Re: [PATCH RFC 2/2] [x86] Optimize copy_page by re-arranging instruction sequence and saving register

[Andi Kleen]

> I tested new and original version on core2, the patch improved performance about 9%,

That's not useful because core2 doesn't use this variant, it uses the
rep string variant. Primary user is P4.

> Although core2 is out-of-order pipeline and weaken instruction sequence requirement, 
> because of ROB size limitation, new patch issues write operation earlier and
> get more parallelism possibility for the pair of write and load ops and better result.
> Attached core2-cpu-info (I have no older machine)

If you can't test the CPUs who run this code I think it's safer if you
add a new variant for Atom, not change the existing well tested code.
Otherwise you risk performance regressions on these older CPUs.

-Andi

-- 
ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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