tcp bandwidth on athlon
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Quoted 4 lines · Nivedita Singhvi
Hmm, so if K6 and Xeon can scrounge up 80% of pipe performance, why is the Athlon an order of magnitude off at 8%? How did your Athlon perform in other tests relative to these other procs?
The pipe test basically tests copy_from_user()/copy_to_user(). The standard implementation of these macros (essentially rep ; movsl) doesn't exploit the Athlon very well - it is not good at this instruction. AFAIK Intel CPUs have an faster microcode implementation for this.
You could likely do better on Athlon with a copy*user that uses an unrolled loop with explicit movls or even SSE. [similar to the implementation the x86-64 port uses, but without the NT instructions]
-Andi