Re: sendfile+zerocopy: fairly sexy (nothing to do with ECN)

From: Andrew Morton (andrewm@uow.edu.au)
Date: Sun Jan 28 2001 - 11:05:16 EST


jamal wrote:
>
> PS:- can you try it out with the ttcp testcode i posted?

Yup. See below. The numbers are almost the same as
with `zcs' and `zcc'.

The CPU utilisation code which was in `zcc' has been
broken out into a standalone tool, so the new `cyclesoak'
app is a general-purpose system load measurement tool.
It's fascinating to play with, if you're into that sort
of thing.

`cyclesoak' was used to measure ttcp-sf and NFS/UDP client
and server throughput. The times()-based instrumentation
inside ttcp-sf doesn't (can't) give correct numbers. 2-4% CPU
at 100 mbps? We wish :)

The zerocopy patch doesn't seem to affect NFS efficiency at
all. Confused.

Excerpt from the rapidly swelling README:

NFS/UDP client results
======================

Reading a 100 meg file across 100baseT. The file is fully cached on
the server. The client is the above machine. You need to unmount the
server between runs to avoid client-side caching.

The server is mounted with various rsize and wsize options.

  Kernel rsize wsize mbyte/sec CPU

  2.4.1-pre10+zc 1024 1024 2.4 10.3%
  2.4.1-pre10+zc 2048 2048 3.7 11.4%
  2.4.1-pre10+zc 4096 4096 10.1 29.0%
  2.4.1-pre10+zc 8199 8192 11.9 28.2%
  2.4.1-pre10+zc 16384 16384 11.9 28.2%

  2.4.1-pre10 1024 1024 2.4 9.7%
  2.4.1-pre10 2048 2048 3.7 11.8%
  2.4.1-pre10 4096 4096 10.7 33.6%
  2.4.1-pre10 8199 8192 11.9 29.5%
  2.4.1-pre10 16384 16384 11.9 29.2%

Small diff at 8192.

NFS/UDP server results
======================

Reading a 100 meg file across 100baseT. The file is fully cached on
the server. The server is the above machine.

  Kernel rsize wsize mbyte/sec CPU

  2.4.1-pre10+zc 1024 1024 2.6 19.1%
  2.4.1-pre10+zc 2048 2048 3.9 18.8%
  2.4.1-pre10+zc 4096 4096 10.0 34.5%
  2.4.1-pre10+zc 8199 8192 11.8 28.9%
  2.4.1-pre10+zc 16384 16384 11.8 29.0%

  2.4.1-pre10 1024 1024 2.6 18.5%
  2.4.1-pre10 2048 2048 3.9 18.6%
  2.4.1-pre10 4096 4096 10.9 33.8%
  2.4.1-pre10 8199 8192 11.8 29.0%
  2.4.1-pre10 16384 16384 11.8 29.0%

No diff.

ttcp-sf Results
===============

Jamal Hadi Salim has taught ttcp to use sendfile. See
http://www.cyberus.ca/~hadi/ttcp-sf.tar.gz

Using the same machine as above, and the following commands:

Sender: ./ttcp-sf -t -c -l 32768 -v receiver_host
Receiver: ./ttcp-sf -c -r -l 32768 -v sender_host

                                                        CPU

    2.4.1-pre10-zerocopy, sending with ttcp-sf: 10.5%
    2.4.1-pre10-zerocopy, receiving with ttcp-sf: 16.1%

    2.4.1-pre10-vanilla, sending with ttcp-sf: 18.5%
    2.4.1-pre10-vanilla, receiving with ttcp-sf: 16.0%

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This archive was generated by hypermail 2b29 : Wed Jan 31 2001 - 21:00:29 EST