Subject: Linux single copy pipes
To: None <>
From: John Fremlin <>
List: tech-kern
Date: 05/07/2001 18:17:01
Manfred Spraul made a patch for single copy pipes under Linux. For
example, on my 300 MHz AMD K6-2, linux-2.4.4,

Brett McCoy <> writes:


> cpu0: Intel Pentium Pro (686-class)
> total memory = 127 MB

Brett's CPU is slower than mine (only 200 Mhz) and I have more memory
(320Mb) so the comparison is unfair. Unfortunately I don't have a
native NetBSD install on my PC so I can't do it properly.

Without single copy:

> Pipe bandwidth: 48.36 MB/sec

With std lmbench 2beta3 I get about 45 (+- 2) Mb/s.


> Pipe latency: 65.5195 microseconds

With std lmbench I get about 27 (+- 1) usec.

Single copy:

> Pipe bandwidth: 194.09 MB/sec

About 59.5 (+-0.6) Mb/s :-(


> Pipe latency: 43.2424 microseconds

About 22 usec.

So from this very crude comparison Linux rules the latency, but the
loses bigtime on the single copy bandwidth (did you people hack
lmbench for a bigger request size?)