[GCJ] Performance of GUI applications on embedded systems

Sat Nov 8 11:40:00 GMT 2008

Andrew Haley wrote:
> ffileppo wrote:
>>>>> Here's one improvement. If you can get rid of the places in the GTK peers
>>>>> where class and method lookups are performed at runtime you'll probably
>>>>> have a fix. This shouldn't be a massive amount of work, just rather
>>>>> boring.
>>>>>>>>>> In gcj,
>>>>>>>>>> * Compiled java code is quite fast.
>>>>> * Class lookup by name is slow.
>>>>> * Calling JNI code from compiled java code is quite fast.
>>>>> * Calling compiled java code from JNI code is slow.
>>>>> * Exceptions are slow.
>>>> I'm testing your patch on my embedded system and now I can see that GUI performance are very much better (particularly during application startup).
>>>>>>>> Thank you so much!
>>>>>>>> However running my test case (please see my first post) I see that CPU usage is always at 100% (after the application is running),
>>>> so the responsiveness is still not very good.
>>> What do you expect? You're setting up a Timer with a delay of
>>> 0 milliseconds between events, and it's running continuously.
>>>>>> Andrew.
>>>>> You're right.
>> However I'm experiencing slowness when testing some other GUI sample application (e.g. the test case attached at the end).
>>>> In this particular test case, the application takes a lot of time to startup (compared to the same device, running WinCE and CrEme JVM) and during start up the CPU usage is always at 100%.
>>>> After startup, I'v also noticed that highlighting and/or clicking a certain number of times on buttons cause the application to hang and after that the CPU usage is always 100%.
>> I've identified some serious GTK locking problems with this version of gcj.
>> I'm investigating.

Found a very silly (:-) merge error in CairoGraphics2D.c.
This fixes it.
I don't think there should be any differences between the GTK peers
in Classpath and gcj, should there? Or indeed, and differences between
the CNI code in Classpath and gcj.
Andrew.
Index: gnu_java_awt_peer_gtk_CairoGraphics2D.c
===================================================================

--- gnu_java_awt_peer_gtk_CairoGraphics2D.c	(revision 141575)
+++ gnu_java_awt_peer_gtk_CairoGraphics2D.c	(working copy)
@@ -351,7 +351,6 @@
 for (i = 0; i < n; i++)
 {
 PangoFcFont *font = JLONG_TO_PTR(PangoFcFont, fonts[i]);
- gdk_threads_leave ();
 /* Draw as many glyphs as possible with the current font */
 int length = 0;
