AW: [squid-users] AW: any chance to optimize squid3?

From: Fuhrmann, Marcel <>
Date: Sat, 24 Nov 2012 07:52:16 +0000

Hello Amos,

I've installed a test squid server. I'm using CentOS 6.3 (2GB Ram, 2 CPU, RAID10 for caching folder). I followed this guides:

And now i'm also using kerberos to authenticate to Windows 2008. And the best: It's working :-)

Here my config:

cache_mem 64 MB
cache_dir aufs /var/spool/squid 8000 256 256
cache_effective_user squid
cache_replacement_policy heap LFUDA
maximum_object_size 1000 KB
maximum_object_size_in_memory 128 KB
memory_replacement_policy heap GDSF
error_directory /usr/share/squid/errors/de-de

auth_param negotiate program /usr/lib64/squid/squid_kerb_auth
auth_param negotiate children 10
auth_param negotiate keep_alive on

acl snmplux snmp_community kj3v45hv345j23
#acl LAN src
acl manager proto cache_object
acl localhost src
acl to_localhost dst
acl SSL_ports port 443
acl Safe_ports port 80 # http
acl Safe_ports port 21 # ftp
acl Safe_ports port 443 # https
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 AUTH proxy_auth REQUIRED

snmp_access allow snmplux localhost
http_access allow AUTH
#http_access allow LAN
http_access allow manager localhost
http_access deny manager
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow localhost
http_access deny all
icp_access deny all
htcp_access deny all

hierarchy_stoplist cgi-bin ?
access_log /var/log/squid/access.log squid
cache_log /var/log/squid/cache.log squid
refresh_pattern ^ftp: 1440 20% 10080
refresh_pattern ^gopher: 1440 0% 1440
refresh_pattern -i(/cgi-bin/|\?) 0 0% 0
refresh_pattern . 0 20% 4320
icp_port 0
http_port 3128
snmp_port 3401

Two questions about it:

How can I grant internet access to a ADS group called "INTERNET". The example in the guide doesn't work for me. If this is working, I will switch all my users to this server and discard my old one. Then I'm able to test, if this config is more efficient.

Is there any regulation how to arrange a squid config? OK, the rules need a special order to work correct, but what about the rest?

Thanks for your help!

-----Ursprüngliche Nachricht-----
Von: Amos Jeffries [] 
Gesendet: Freitag, 16. November 2012 23:58
Betreff: Re: [squid-users] AW: any chance to optimize squid3?
The big issues you have are:
  * using NTLM. This seriously caps the proxy performance and capacity. 
Each new TCP connection (~30 per second from your graphs) requires at least two full HTTP reqesut/reply round trips just to authenticate before the actual HTTP response can begin to be identified and fetched.
* using group to base access permissions. Like NTLM this caps the capacity of your Squid.
* using a URL helper. Whether that is a big drag or not depends on what you are using it for and whether Squid can do that faster by itself.
These are your big performance bottlenecks. Eliminating any of them will speed up your proxy. BUT whether it is worth doing is up to you.
All of the evidence is (to my eye anyway) looking like NTLM being the cause of a temporary bandwidth flood around 13:30-13:45. Whether that is matching your report of "slow" is unknown. You should drop NTLM anyway if you can. It has officially been deprecated by MS and Kerberos is far more efficient and faster.
 From your graphs I note your peak traffic time of 13:15-13:45 shows a bandwidth peak of almost 10Mbps. I guess that these are the "slow" times your users are complaining about? - it is expected that things slow down when the bandwidth completely fills up although whether you are working off 10Mbps NIC is unknown. TCP graphs are showing an increase in the early part of the peak, and HTTP response rate peaks out in the second half. This is consistent with NTLM sucking up extra bandwidth authenticating new connections - first half of the peak is initial TCP setup + HTTP first requests, HTTP peaks in a burst of challenge responses followed by both further HTTP as the clients send the handshake re-request and the actual HTTP response part of the cycle happens (client requests peak in both halves, out bandwidth peaks only in the second half with the larger responses involved).
  The HTTP response time quadruples (20ms -> 80ms) in the 15 minutes
*before* these peaks occur and HIT ratio jumps by ~15% over the peak traffic time. Consistent with a number of requests queueing at the authentication and group lookup stages.
I guess you have 10Mbps NIC, which could be part of the issue. Squid should be able to handle 50-100 req/sec despite NTLM and yet it is maxing out at 30. But 9.7Mbps is a suspicious number for peak bandwidth. 
If your NIC are faster the above can all happen just the same on faster NIC due to processing time / response time for the helpers.  But on faster NIC I would expect to see higher bandwidth, TCP connection rates, and longer HTTP response times on the held up connection attempts.
Alternatively, after 16:30 and before 07:30 the TCP speeds are ramping up/down between the daily normal and overnight low traffic throughput. 
Squid is designed on a traffic-driven event model. We have some issues that when there is low enough traffic per-millisecond there are several components in Squid which start taking ~10ms pauses between handling events (to preserve against 100% CPU cycling checking for nothing) and can cause the response times to increase somewhat. If your reports are comign in from the earlybirds or late workers this is probably the reason.
On 16/11/2012 11:50 p.m., Fuhrmann, Marcel wrote:
> I have some performance graphs. Maybe they will help:
I see two other weird things.
  * FQDN cache is not storing DNS responses for some reason - that will cause a little bit of slowdown.
* the packets/sec graph at your peak traffic (10Mbps) is only showing
~500 packets. Do you have jumbo packets enabled on your network? If so it looks like you are getting bandwidth in packets of ~200KB which will cause some requests to be held up slightly behind other large packets. 
This is an effect which gets worse as the bandwidth pipes approach full. 
There is no matching congestion control ICMP traffic peak showing up - so I'm not sure of the accuracy there.
Received on Sat Nov 24 2012 - 07:52:41 MST

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