Is there a way to know how much memory is consumed by each Eclipse plugin separately?
I would be quite surprised if this were possible, because you would have to have an unambiguous way of determining which plugin "owned" a particular object on the heap.
I don't know any generic answer but maybe it is possible to get the memory usage of some plugins: as the framework loads plugins on demand if you can read the heap size before and after the activation of the plugin it might give an idea.
To check which plugins are loaded, the 'ss' command can be used in the OSGi console.
Take a heap dump and analyse it with e.g. the Eclipse Memory Analyser.
For more information, see Analyzing Equinox Bundle Dependencies with Memory Analyzer
Eclipse 3.1 has a built-in Memory Monitor (aka Heap Status) Plugin, which is a part of org.eclipse.ui.workbench_3.1.0.jar You have to run Eclipse in debug mode for seeing the monitor in right lower corner.
Also check FreeMem plugin:FreeMem plugin
In Eclipse you can uninstall-->measure memory-->install-->repeat cycle
That way you can find out about any/all memory utilization of each plugin. Good luck with this task. I'd be interested to see the results because I see that some plugins utilize much more memory then others.