Re: zero-copy TCP

From: Jes Sorensen (
Date: Mon Sep 04 2000 - 10:20:24 EST

>>>>> "Ingo" == Ingo Molnar <> writes:

Ingo> On Mon, 4 Sep 2000 wrote:

>> The experiment showed the following prefetching could reduce 20-30%
>> of csum_partial_copy_generic() execution time.

Ingo> Please test it and post the numbers. csum_partial_copy_generic()
Ingo> already does prefetching - the real test would be to check
Ingo> lat_tcp and bw_tcp numbers over gigabit, with and without this
Ingo> patch applied. (the same numbers over localhost dont really
Ingo> count.) Eg. we had smart KNI-based memcpy routines as well, and
Ingo> it turned out that bw_tcp over gigabit actually got
Ingo> slower. [testing over 100mbit isnt enough obviously because x86
Ingo> CPUs csum much faster than that.]

Thats a surprise to me, I remember better performance when I played
with Doug's KNI patches back in the beginning.

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