Messages in this thread | | | Date | Fri, 12 Oct 2012 15:35:54 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH RFC 2/2] [x86] Optimize copy_page by re-arranging instruction sequence and saving register |
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> 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@linux.intel.com -- Speaking for myself only.
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