network performance tuning

[Greg]

As I have mentioned before I am working on creating various Fedora
server loads at http://www.packetstorm.org/fedprj/

So far I have the core load done and I am almost done with the log
server load http://www.packetstorm.org/fedprj/core/log_server.htm

While looking into network performance tuning options, I ran across the
following setting tweaks that could be made on the system

net.ipv4.tcp_rmem = 10000000 10000000 10000000, sets min/default/max TCP
read buffer, default 4096 87380 174760

net.ipv4.tcp_wmem = 10000000 10000000 10000000, sets min/pressure/max
TCP write buffer, default 4096 16384 131072

net.ipv4.tcp_mem = 10000000 10000000 10000000, sets min/pressure/max TCP
buffer space, default 31744 32256 32768

net.ipv4.tcp_sack=0 turn SACK support off, default on

net.ipv4.tcp_window_scaling = 0, turn TCP window scaling support off,
default onnet.core.hot_list_length = 300000, maximum number of skb-heads
to be cached, default 128

net.ipv4.tcp_max_tw_buckets = 2000000, sets TCP time-wait buckets pool
size, default 180000

net.ipv4.tcp_timestamps=0 turns TCP timestamp support off, default on

net.core.rmem_max=524287 maximum receive socket buffer size

net.core.wmem_max=524287 maximum send socket buffer size

net.core.rmem_default=524287 default receive socket buffer size

net.core.wmem_default=524287 default send socket buffer size

net.core.optmem_max=524287 maximum amount of option memory buffers,
default 10240

net.core.netdev_max_backlog=300000 number of unprocessed input packets
before kernel starts dropping them, default 300


For the log server I focused on socket buffers as I noticed that udp
packets were getting dumped due to high syslog volume.  But does anyone
here have a really good explanation on the settings above? Can they be
used as a general performance tweak on any system configuration? I read
in one place some of these settings should not be used on multi-user
systems. 

Is there a Fedora tuning guide? Any recommendations for a good baseline?
Is there a reasoning behind the default Fedora settings listed above?
Not that I disagree but that I want to understand it.

FYI here is a SPEC doc I found in google where some of these settings
were mentioned

http://216.239.41.104/search?q=cache:JrEBIcPgWoIJ:www.specbench.org/web99/results/res2002q1/web99-20020205-00174.pdf+net.core.wmem_default%3D&hl=en&ie=UTF-8

thanks

Greg