Module Name:	src
Committed By:	tls
Date:		Mon Sep 29 21:39:35 UTC 2003

Modified Files:
	src/sys/netinet: tcp_usrreq.c

Log Message:
Increase default socket-buffer sizes from 16K to 32K.  This increases
throughput significantly in a wide variety of test cases, including
local gigabit ethernet with both jumbo and standard frames,
transcontinental (U.S.) connections with e2e bandwidths ranging from
10Mbit/sec to 155Mbit/sec, and on a variety of test connections
between the NetBSD Project public servers and machines in Australia.

The impact of this change is less dramatic for high-delay connections
when Path MTU is in use but still measurable.

For optimal performance on local gigabit networks, a higher socket
buffer size (at least 64K) will still yield a substantial improvement
in performance, but 32K gets us most of the way there in my test
cases, with only a cost of _doubling_ memory use per socket rather
than _quadrupling_ it.

N.B. Windows NT, at least since Win2k SP2, uses a default socket buffer
     size (or their analogue thereof) of 64K, which is a useful data
     point.


To generate a diff of this commit:
cvs rdiff -r1.83 -r1.84 src/sys/netinet/tcp_usrreq.c

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