Since few days before the upgrade of the home server to Fedora Linux Core 3 I was seeing high load spikes from SpamAssassin. After the upgrade, my load average stayed at 10-15 almost the whole day. I was trying to fix it, but to no avail. At first, I have switched off the Bayes filtering, thinking that that is the part to be blamed. It didn’t help. Than I forced SpamAssassin to run in non-Unicode environment, thinking that that might improve things. Nope.
After playing some more with configuration and Googling, I decided to visit #spamassassin IRC channel. In a matter of seconds I was pointed to the this bug report. I will be trying the posted patches shortly. For now though, a simple change of number of maximum children helped a lot. I have reduced it to 2 from the default value of 5. (Edit /etc/sysconfig/spamassassin)