Re: [squid-users] Squid performance profiling

On Fri, Jun 21, 2013 at 6:17 AM, Alex Rousskov
<rousskov_at_measurement-factory.com> wrote:
> On 06/20/2013 02:00 AM, Ahmed Talha Khan wrote:
>
>> My test methodology looks like this
>>
>> generator(apache benchmark)<------->squid<------>server(lighttpd)
> ...
>> These results show that squid is NOT CPU bound at this point. Neither
>> is it Network IO bound because i can get much more throughput when I
>> only run the generator with the server. In this case squid should be
>> able to do more. Where is the bottleneck coming from?
>
> The "bottleneck" may be coming from your test methodology -- you are
> allowing Squid to slow down the benchmark instead of benchmark driving
> the Squid box to its limits. You appear to be using what we call a "best
> effort" test, where the request rate is determined by Squid response
> time. In most real-world environments concerned with performance, the
> request rate does not decrease just because a proxy wants to slow down a
> little.
>
Then the question becomes why squid is slowing down? It is not CPU
bound, neither is it Network bound. What
can cause squid to not utilize all the resources that it can. I agree
to your point of view that in real-world
environments the situation is more like webpolygraph(or spirent,
avalanche for that matter) but best effort tests also
give a good measure of what the proxy(server) can do without breaking
it. Do you see any reason from the perf results/benchmarks
why squid would not be utilizing all CPU and giving out more requests
per second?

> When we want to find the bottleneck, we often tell Web Polygraph to
> increase proxy load until things start to break. In this "persistent
> load" mode, Polygraph does not allow the proxy to determine the request
> rate. It keeps pounding the proxy [at the configured rate], just like
> real users would. I do not know whether ab can do it, but I would not be
> surprised if it can. <plug>Still, I would recommend that you use a
> benchmarking tool designed to test proxies rather than origin servers
> :-).</plug>

I plan to test it with webpolygraph also when I get the due time and
resources. But for now I want to make sense of the lower
numbers. BTW, ab cannot do this constant request rate model testing
>
>
> Cheers,
>
> Alex.
>

--
Regards,
-Ahmed Talha Khan