some questions about Tunning FreeBSD

[Vahric MUHTARYAN]

Hi Everybody 

I red tunning man and some documents on the Internet . I have same question
to undertanding better 


1)in tuning man siad that " Setting vfs.vmiodirenable improve the performans
of sevices that manipulating a large number of file like Web Cache,large
Mail System and News System " 

But I don't agree with it for mail system, or What type of mail systems can
imporved with this settings ... For example we are using only POP3 at this
moment users are connecting their mailbox and download mail .... I think
that at this moment Caching Directory or Files not important ?! Does it
usable with IMAP for example-or-How store mails on Mail Server?Am I wrong ?!



2)Can I set Kern.maxfilesperproc=0 because I don't want to seperate
maxfilesize for seperate process ?! I mean I don't want to limit it for any
process ?! 

3)I think setting kern.pc.somaxconn is not necessary because all programs
can handle their self listen queue size like Apache and Mail Programs . 

One sentence disturb me in tunning man, "Larger listen queue also do a
better job of fending off denial service attack" 

I can't imagine How ?! What difference between large or short listen queue
for attacker ?! 


4)What is net.local.stream I don't find any explanation in tunning man. 


Thanks again everyody 
Vahriç