Ajuda - Squid fazendo pouco cache

Ola amigos estou com um problema com meu squid ele esta fazendo puco cache .
usando o Debian 6
Core i5 650
4 GB memoria ddr3
800 Gb disponivel pra cache 7200rpm

Aqui meu scripit do squid.

############## Scripit #####################

http_port 3128 transparent
visible_hostname fenix

# ConfiguraÃ§ do cache
cache_mem 3200 MB

maximum_object_size_in_memory 8 MB
maximum_object_size 1024 MB
minimum_object_size 0 KB

cache_swap_low 85
cache_swap_high 90
cache_dir ufs /var/spool/squid 125000 64 256

# LocalizaÃ§ do log de acessos do Squid
cache_access_log /var/log/squid/access.log

dns_nameservers 200.225.197.37 200.225.197.17

refresh_pattern ^ftp: 15 20% 2280
refresh_pattern ^gopher: 15 0% 2280
refresh_pattern . 15 20% 2280

acl all src 0.0.0.0/0.0.0.0
acl manager proto cache_object
acl localhost src 127.0.0.1/255.255.255.255
acl SSL_ports port 443 563
acl Safe_ports port 80 # http
acl Safe_ports port 21 # ftp
acl Safe_ports port 443 563 # https, snews
acl Safe_ports port 70 # gopher
acl Safe_ports port 210 # wais
acl Safe_ports port 1025-65535 # unregistered ports
acl Safe_ports port 280 # http-mgmt
acl Safe_ports port 488 # gss-http
acl Safe_ports port 591 # filemaker
acl Safe_ports port 777 # multiling http
acl Safe_ports port 901 # SWAT
acl purge method PURGE
acl CONNECT method CONNECT

http_access allow manager localhost
http_access deny manager
http_access allow purge localhost
http_access deny purge
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports

#Erros pagina
error_directory /usr/share/squid/errors/Portuguese

http_access allow localhost
http_access allow wifi

# Bloqueia acessos externos
http_access deny all

########### fim do scripit ##############