lkml.org 
[lkml]   [2000]   [Oct]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: LMbench 2.4.0-test10pre-SMP vs. 2.2.18pre-SMP
Date
> The pipe bandwidth is intimately related to pipe latency.  Linux pipes
> are fairly small (only 4kB worth of data buffer), so they need good
> latency for good performance.
...
> The pipe bandwidth could be fairly easily improved by just doubling the
> buffer size (or by using VM tricks), but it's not been something that
> anybody has felt was all that important in real life.

A while ago I hacked 2.2.17 to use larger pipe buffers. On my own pure
throughput benchmark (two processes ping-pongging one buffer's worth of data
on a single-CPU system), buffers larger than 4KB hardly gave any advantage.
64KB buffers were marginally (10-20%) faster, but performance dropped quite
considerably after that (cache effects, maybe...).

After seeing these results I simply assumed that 4KB had been deliberately
chosen as the optimal buffer size, rather than by luck =).

Now, Dave Miller's kiobuf pipes may change the picture somewhat...

Dan

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:41    [W:0.047 / U:0.220 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site