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Date: Fri, 12 Oct 2012 15:35:54 +0200 From: Andi Kleen <andi@...stfloor.org> To: "Ma, Ling" <ling.ma@...el.com> Cc: Andi Kleen <andi@...stfloor.org>, "mingo@...e.hu" <mingo@...e.hu>, "hpa@...or.com" <hpa@...or.com>, "tglx@...utronix.de" <tglx@...utronix.de>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH RFC 2/2] [x86] Optimize copy_page by re-arranging instruction sequence and saving register > 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@...ux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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