We encounter this problem a lot: the extremely popular and oft-used Admin Menu module causes performance problems.
Here is an example from a site we recently did a Drupal performance assessment for.
Executed 3,169 queries in 584.11 milliseconds. Page execution time was 4,330.86 ms.
As you can see, the number of queries per request is horrendous, and the site is a resource hog if left in that state.
There were several reasons that were causing excessive number of queries leading to excessive page load time, and general slowness and resource usage.
The key here is that the context module was doing a cache_set() and that was triggering Admin Menu to rebuild its menus.
We diagnosed the problem, and were able to get over it by disabling the following modules:
- ND Context
- Context Layout
- Context UI
- Admin Menu
After disabling the above modules, we were able to get much better response and far less queries, after we did that, as follows:
Executed 245 queries in 59.41 milliseconds. Page execution time was 866.24 ms.
Orders of magnitude better ...
We are told, but have not verified, that the 3.x branch is supposed to fix some of the performance issues of Admin Menu.