very slow jni code callbacks

Herman ten Brugge
Mon Sep 28 19:47:00 GMT 2009

On 09/28/09 21:01, Tom Tromey wrote:
> Andrew>  This calls _Jv_GetTypesFromSignature, which in turn iterates though
> Andrew>  all the class loaders looking up the types of all the arguments.
> Andrew>  But as far as I can see this is a pointless waste of time: the only
> Andrew>  use of the type of each argument is to determine whether it's a
> Andrew>  primitive type or not, and we could certainly have done that when
> Andrew>  we created the jmethodID.
> Yeah, this could use some improvement.
> Even a variant of _Jv_GetTypesFromSignature that did less work would
> help
I did try some older gcc releases because I once had good
results for callbacks.
The 4.1.2 release shows some different results.

#                       open jdk        gcj
# no_jni                 1.48              12.12        (  8 times slower)
# jni                   66.70             200.93        (  3 times slower)

So there must be a change some time ago that made this
much slower.


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