WordPress › P3 (Plugin Performance Profiler)

See which plugins are slowing down your site. This plugin creates a performance report for your site.

First, profile your site. The scanner generates some traffic on your site and monitors your site's performance on the server, then shows you the results. With this information, you can decide what action to take.
After profiling, you'll see a breakdown of relative runtime for each plugin.
Callouts at the top give you quick information like how much load time (in seconds) is dedicated to plugins and how many database queries your site is running per page.
The detailed timeline gives you timing information for every plugin, the theme, and the core for every page during the profile. Find out exactly what's happening on slow loading pages.
You can toggle each series on and off to customize this timeline for your precise needs.
The query timeline gives you the number of database queries for every page during the profile. Find out which pages generate the most database queries.
Keep a history of your performance scans, compare your current performance with your previous performance.
Full in-app help documentation
Send a summary of your performance profile via e-mail. If you want to show your developer, site admin, hosting support, or a plugin developer what's going on with your site, this is good way to start the conversation.