Messages in this thread | | | Date | Wed, 15 Dec 2010 10:00:55 -0800 (PST) | Subject | Re: Big git diff speedup by avoiding x86 "fast string" memcmp | From | David Miller <> |
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From: Boaz Harrosh <bharrosh@panasas.com> Date: Wed, 15 Dec 2010 15:15:09 +0200
> I agree that the byte-compare or long-compare should give you very close > results in modern pipeline CPUs. But surly 12 increments-and-test should > show up against 3 (or even 2). I would say it must be a better plan.
For strings of these lengths the setup code necessary to initialize the inner loop and the tail code to handle the sub-word ending cases eliminate whatever gains there are.
I know this as I've been hacking on assembler optimized strcmp() and memcmp() in my spare time over the past year or so.
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