Slow RPC calls in development mode (GWT)

When I run my GWT application in development mode (included Jetty) in Eclipse (Helios), RPCs seem to be very slow. Firebug says that they should be ok (mostly < 1sec) but in fact I have to wait about 10-15 seconds. Browser window is freezed开发者_如何学Python for that time... Everything else runs quite performant, on RPC is a problem.

Running with noserver option using a Tomcat 6, I have the same problem. But without the develpment mode (on same Tomcat) everything is fine.

Does anybody know, whats the problem with dev mode?

Edit:

I tried to increase memory with -Xmx1024m but it doesn't help.

Probably Eclipse shares resources with jetty in the development mode. Try to increase memory available for Eclipse. (I can observe similar situation on my dev box)