I just launch it and was so surprised that I wanna blog about it. I don't know how it works but Eclipse starts as fast enough for me (maybe faster than IBM's JVM, I don't know) and I can't beleive it! :-D
Read previous blog to have instructions to build it (and again thanks to Sun, Gary Benson and all those who make it possible!)
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Hi,
RépondreSupprimerThis is not unexpected. Interpreters are well-known to startup faster than JITs. This is the reason IBMs VM and Hotspot both use a "mixed-mode" of execution.
If a VM only has a JIT, it must compile a method before it can execute it. Obviously, on startup, no method has yet been compiled. This means a large amount of the code it executes will need compiling first. Therefore, a large amount of the startup time will be spent JIT compiling rather than executing code. Moreover, as JITs become more aggressive (and therefore slower) the overhead of compilation at startup becomes greater and greater.
The solution is to execute everything using the interpreter first, and only compile "hot" methods. This dramatically improves startup times.
After startup the number of new methods compared to already compiled methods will be much lower. However, even here, executing methods in the interpreter first has advantages. For little used methods, the cost of compilation will be higher than the performance improvement of the native code over interpretation.
Rob.
Hi Rob,
RépondreSupprimerThanks for your explanation and congratulation for your "JamVM on iPhone"! ;-)
No way!
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