On Sep 30, 2005, at 7:51 AM, Chris McFarling wrote:
/etc/sysctl-macosxserver.conf states the following:
# Some sysctl variables administrators may consider setting in
/etc/sysctl.conf:
#
# This sets a threshold that triggers increasing the send/recv
windows for
TCP
# connection from 32K to 64K to improve some file downloads.
# If your server has a lot of memory and serves only local traffic
(like AFP
cli
ents
# on local LAN) you may want to increase this value beyond its
default of
256 pc
bs.
#
# net.inet.tcp.sockthreshold=512
When it says"256 pcbs", what does that mean?
That's the number of TCP control blocks, which is approximately the
number of active TCP connections.
Also, how does the triggering
mechanism work...when does the OS use 32K windows and when does it
use 64K
windows?
The OS uses 64 K windows as long as the number of TCP connections is
less than net.inet.tcp.sockthreshold.
When the number of TCP connections is greater
net.inet.tcp.sockthreshold the stack will use the values of
net.inet.tcp.recvspace and net.inet.tcp.sendspace
The reason I ask is because I actually want to set the window size
to 18K.
I'm doing some testing and want to see if a smaller window size will
increase performance on my network. In doing so I'm trying to
understand OS
X's behavior though.
To disable this mechanism and force the stack to always use a 18K you
simply need to set net.inet.tcp.sockthreshold to zero
