Original issue
Since I changed the version from 1.6.3. to 1.6.4 I get serious performance problems working together with GWT in hosted mode.
Update 18/04/2012
The issue is reproductible also in 1.6.4.1 in dev environment.
By now the best is to downgrade to 1.6.3
Update 09/07/2012
According to Kris Giesing:
This is still not fixed in 1.7.0. A request that takes 330ms to process in 1.4.3, and 415ms to process in 1.6.3, takes 13740ms to process in 1.7.0. That’s from timing the Java analysis code (no I/O) – almost a 40x slowdown.
Update 09/08/2012
Google acknowledged the problem in the issue 7282 of google appengine’s public issue list.
This is a confirmed performance regression in 1.6.4. We (Google) are putting together a patch that contains a fix and we’ll make it available as soon as we can.
Sorry for the trouble
(I’m the guy who introduced the regression)