Subject: CVS commit: src/sys/dev/pci
To: None <>
From: Thor Lancelot Simon <>
List: source-changes
Date: 09/10/2003 04:02:19
Module Name:	src
Committed By:	tls
Date:		Wed Sep 10 04:02:18 UTC 2003

Modified Files:
	src/sys/dev/pci: if_wm.c

Log Message:
Add support for jumbo (9K) frames.  Add support for larger receive
descriptor sizes if larger mbuf clusters are in use -- currently
commented out because, for some reason, transmit doesn't work at
all with large mbuf cluster sizes.

Note that using actual 9K frames is a _lot_ less efficient than
using frames that are a little smaller than 8K so that they fit
in one or two pages (instead of two or three) and avoid the extra
chained descriptor with only 1K of data in it, too.  TCP will
segment things just fine for an 8K total packet size, just as it
does for 1500-byte packets.

On my system, using "mtu 8000" with ifconfig, I get an almost 50%
performance boost for TCP (930Mbit/sec instead of 660Mbit/sec) over
1500-byte frames.  "mtu 9000" yields only 770Mbit/sec.

To generate a diff of this commit:
cvs rdiff -r1.40 -r1.41 src/sys/dev/pci/if_wm.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.