I am having a huge difference in performance in a page refresh from a single client for the same version of Drupal (6.20) between a fresh install of Drupal and the same version but with a lot of extra modules downloaded and enabled.
The cpu we are using is an intel Xeon quad core (though we are only using 2 cores in our VM). It is an E5345 processor with 8MB of L2 cache, a clock speed of 2.33GHz and FSB speed of 1333MHz.
For a fresh install of Drupal: we see a load on a single core of about 9-10% for about 1 – 1.5 seconds from both IE and Firefox clients
Drupal with a lot of extra modules downloaded and enabled:
a.) Firefox client: 70-80% usage on a single core for about 2-3 seconds
b.) Internet Explorer client: both cores hit the 70-80% usage for about 4-5 seconds
If the client is from Firefox then the CPU usage is around 8 times higher for a SINGLE core for Drupal and takes double the time to complete with a lot of extra modules installed.
If the client is from Internet Explorer then the CPU usage is around 8 times higher for BOTH cores for Drupal and takes three times to complete with a lot of extra modules installed.
Is this normal for Drupal with a lot of extra modules installed to use 8 times more CPU?
Is this normal for Drupal with a lot of extra modules installed and Internet Explorer is the client to use double the cores compared to if Firefox is the client?
Besides the obvious solution of eliminating some of these extra modules which are needed for the extra functionality they provide how can I get Drupal to use less of the CPU when extra modules are installed?
Thanks,
John