[squid-users] I want to know the concerns of load testing

[Alex Rousskov]

On 10/1/20 10:15 PM, m k wrote:

> 1. How much will CPU Usage increase if NTLM authentication is enabled?

Depends on the portion of requests that need to be authenticated,
credentials caching effectiveness, and authenticator response times.
Nothing is easy in performance testing, but it is often easier to
measure performance than to predict it -- good proxy benchmarking tools
support testing proxy authentication.


> 2. Are there any concerns other than CPU Usage in Squid?

On servers dedicated to Squids, CPU usage is not really a concern as
such. It is a convenient but often misleading proxy (i.e. indirect
measure) for real concerns. The real concerns are errors, response times
and, in some environments, bandwidth usage. A good benchmark should
report those measurements.


> 3. When I enabled the cache in this test, the CPU Usage decreased,
> but in general, does the Squid cache increase the CPU Usage?

The answer depends on many factors such as document hit ratio, byte hit
ratio, the portion of the contents that comes from the disk cache
(rather than memory cache), hot subset, and server delays. Bugs
notwithstanding, if caching is worth enabling at all, then a correctly
configured cache decreases CPU usage in most environments (because it
decreases the amount of work that Squid should do for an average
transaction).

Please keep in mind that benchmarking a _caching_ proxy correctly is far
from trivial! Make sure your setup does not measure performance of a
cache with artificially high (or low) hit ratio, performance of a
virtually empty cache, etc.


HTH,

Alex.