High usage of mbufs

[Michael VInce]

Hi guys
On one of my web servers I have a really high usage of mbuf clusters in 
use on a web server that does about 3million hits a day.
4294914731/262144 mbuf clusters in use (current/max)
Does any one know why this is? I was thought it may of been hit by a 
small syn flood that went un noticed and that the current mbuf stat is 
failing to update its real usage, but the number does move every time I 
run netstat -m
This is a dual P4 machine with 4gigs of ram that was setup before 5.4 
was release, so it could be considered 5.3 stable.
5.4-PRERELEASE #0: Mon Feb 28 20:01:43 EST 2005

netstat -m
352955 mbufs in use
4294914731/262144 mbuf clusters in use (current/max)
0/27/6656 sfbufs in use (current/peak/max)
4177412 KBytes allocated to network
0 requests for sfbufs denied
0 requests for sfbufs delayed
415 requests for I/O initiated by sendfile
2300 calls to protocol drain routines