squid with large cache

Hi,

I am running squid v1.1.5 on Solaris 2.5.1. Cache size is 32M
disk cache is 512M. Low and high watermarks are 75 and 90. Everything else
is the same as in default config file.
 Machine is entreprise ultra 1000 with 256M memory and SSA attached.

When cache reaches high watermark it takes squid about 2-5 minutes to
do a clean up. Which is of course unacceptable. Any ideas what parameters
I have to tweak. Many thanks.

--
 Sasha Mikheev                      Linux -- put a penguin in your processor
 System Manager at Netvision Israel, Ltd
 Tel  +972-4-8560600 
 http://aldan.netvision.net.il/~sasha