Squid proxy performing extremely slow and sometimes doesn’t work at all

My first hunch would be to sniff the traffic using tcpdump and load it into wireshark to see where the delay is happening.

tcpdump -i any -s 0 -w /tmp/squid.pcap

(If you're doing it over ssh, add "not port ssh" to the end.)

Once you load this into wireshark you should be able to see where the delay appears to be. I'd recommend doing this during a quiet time so there isn't too much traffic obscuring your view. If you can be the only person accessing the proxy at the time, even better.

Likely delays are:

• Browser contacting proxy
• Proxy contacting webserver
• Proxy DNS requests
• Proxy returning response to browser

The fact that there is nothing in the access.log suggests that the requests from clients aren't being routed through Squid at all but something else on the same server.

Could you post more information about your setup, Squid config and what you actually have on the same box (censoring it first of course).