Re: [squid-users] How well does squid perform under stress?

On Wed, 4 Apr 2007, Ben Spencer wrote:

> We have a squid appliance which is very heavy on CPU (which is
> expected). My question isn't really how can I tune it or why is it using
> so much CPU, but rather, how well does squid perform on a busy (CPU
> wise) box?
> I guess another way to ask is, does squid's performance scale linearly
> as the box (CPU specifically) usage increases or does performance
> actually degrade/level off once the CPU is approaches 100% utilization?

Depends on how you're using Squid.

> Another question is: once the system is pushed to a maximum (or beyond),
> are things just slow or should abnormal behavior be expected?

Things will "just" slow down if you have a _simple_ setup. If you are
using something else with squid that competes for CPU (redirector,
journalling filesystem, software RAID, IDE disks (gasp!), etc), squid may
get too bogged down and refuse connections or even coredump and restart
itself.

So, I would say that until you hit 100%, squid is fine (assuming you
haven't reached any other bottlenecks by that time). Once you're at 100%,
though, things get shaky if/when you need more CPU. If you're routinely
hitting 100%, you probably need more CPU and should see about reducing the
amount of work Squid has to do.

--
Justin Dossey
Operations, Podomatic