[Zope] CacheManagers are cool :)

[Seb Bacon]

I've just been experimenting with the RAM Cache manager, and FWIW I thought
I'd share my findings:

I ran some simple tests using ab against a single, dynamic page which has
some display logic both in the filesystem product and dtml.  I cached the
index_html using the default RAM Cache Manager settings.

Without caching, response time appeared to increase in direct proportion to
the number of simultaneous requests up to 10.  Above 10 connections,
response time worsened dramatically.  When there were 15 simultaneous
connections, the response time averaged at approximately 10 seconds.  The
relationship looked logarithmic, but I didn't really take enough samples to
be sure.  Plus, the system I tested it on only has 96Mb RAM, and it was
swapping a bit.

In all cases the cache improved performance.  The average response time was
improved by up to 70% where more than 10 concurrent users were simulated.
There was an improvement of 20% - 25% between 5 and 10 concurrent requests.
There was no significant improvement where there were no concurrent
requests.  The relationship between the number of simultaneous requests and
the response time remained linear across all measured levels of concurrency.

Not exactly a real-life usage scenario, but it sounds impressive :)  Not
sure I understand what the cache keys are for though... is there any more
documentation forthcoming on this?