Re: [squid-users] Multiple Squid Instances

From: viswanathan sekar <>
Date: Wed, 24 Aug 2011 20:42:21 +0530

Thanks for the replying Amos,

I am going to test with CPU affinity with multi-core,

* i will run multiple squid instances in multi-core , that is each
instance run in specific core,

for example squid1 in CPU #0 and squid2 in CPU #1

* with iptables using --probability to load balance the squid

* for caching , instances have separate cache_dir with cache_peer balancing

before trying this i wish to know , it will give better performance ?


On Wed, Aug 24, 2011 at 6:05 PM, Amos Jeffries <> wrote:
> On 24/08/11 21:46, viswanathan sekar wrote:
>> Hi All,
>> I had an argument with my friends telling them that mulitple squid
>> instances in multi-core processors will give better performance with
>> iptables load balancing.
>> Some of my friends disagreed with me telling single squid instance
>> will give same performance.
>> I am really confused,
>> which will give better performacne from the above two?
>> Is squid IO bound or CPU bound ?
> Both.
>  - instances using cache_dir tend to be disk I/O bound
>  - instances using only memory caching tend to be network I/O bound
>  - instances doing much ACL filtering tend to be CPU bound
> With >2 cores you can mix these types to get better overall performance in
> one area or another.
> As for iptables;
>  So far I have had two people indicating a nice req/sec increase using: a
> single instance, single core utilized, identical config, only changing 2 vs
> 1 http_port receiving traffic. We don't know why precisely, I do know that
> two ports means Squid does two accept() per cycle of FD checking.
>  (I forget what the actual increase % mentioned was, no strict measurements
> were taken though).
> NOTE: iptables is just a way of presenting client with one port and using
> this effect for two ports in the background. Same effect was seen with other
> non-iptables methods of spreading the load over two ports (round-robin DNS
> in the one case of that. I expect PAC selection of an instance port would
> work too).
>  Nice project in there if someone wants to research its reliability and
> measure the actual gain/loss metrics.
> NP: Squid makes _extreme_ demands of the disks. If there is anything getting
> in between or trying to utilize them for other purposes (including RAID) the
> disk I/O performance is degraded. Sometimes a lot.
> Amos
> --
> Please be using
>  Current Stable Squid 2.7.STABLE9 or 3.1.14
>  Beta testers wanted for
Received on Wed Aug 24 2011 - 15:12:34 MDT

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