Apache randomly using too much RAM
running a single vBulletin forum on the below server (~300 users average). but for some reason, after a random amount of time (sometimes 60 secs, sometimes much as 12hrs) Apache starts eating the RAM. normally the server runs with about 50% free. but once it starts eating ram, it keeps using it till it's using 100% RAM and close to 1.5gb of SWAP (takes about 3 mins to go from 50% free RAM to using 1.5gb swap). for some reason all the Apache forks just start eating more and more. once i simply stop and restart apache it's fine again until the next 60 secs - 12hrs time it happens
I tried sticking Apache 1.3 (default settings) to see if that fixed the problem, didn't help. still happened. I'm pretty sure it's related to PHP, but unsure what else to try. I've gone through apache's logs, dmesg, everything I can think of and I can't find a cause.
wondering if anyone else ran into this, or had suggestions to try.
server ------------------
dual opteron 242 - 64bit
1gb ram
3gb swap
2.6.8-11-amd64-generic kernel
PHP Version 4.3.10-15
Apache/2.0.54 (apache2-mpm-prefork)
mysql 4.0.24 (x86_64)
Debian Sarge AMD64
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