size of net.inet.tcp.sendspace and net.inet.tcp.recvspace

[Bill Moran]

Yavuz Maşlak wrote:
> hello 
> i want to tune on freebsd4.9, My server has pentium 4, 2.8Ghz, 73*4 Gbyte scsi disk
 > (Raid5), 2Gbyte ram.
> it runs apache 1.3x.
> For max performance, What  does myserver should be size of net.inet.tcp.sendspace
 > and net.inet.tcp.recvspace or other values ?

That's a complicated question.

The default values are pretty reasonable for most uses.  There are only (really) two
reasons you should change them.
1) Each seperate connection allocates sendspace adn recvspace amount of memory.  If
    you have a LOT of connections, this can use up RAM that is better used other
    places.
2) If you're transferring large file across considerable distances, you may hit a
    situation where increasing these increases performance.

With 2G of RAM, I doubt #1 will apply, but it is possible to have so many connections
that it needs to be considered, watch your load.

#2 depends on what your web site is serving.  If it's mostly static HTML pages, then
the default of 32k for send is probably fine.  If it's stuff considerably larger than
that, then it might be worth trying to raise it a bit.  Don't go overboard, or you'll
end up with #1.

If you're letting people upload big files/data, you may want to consider increasing
recvspace ... same rules apply.

You're probably best off leaving the default values, unless you notice performance
problems.  If that happens, try increasing (or decreasing) the value that seems
appropriate and test to see if it's improved things.  Keep an eye on your memory
usage to ensure you don't increase anything to where #1 starts to occur.

-- 
Bill Moran
Potential Technologies
http://www.potentialtech.com