MethodHandle performance

[Claes Redestad]

Hi Stephen,

this is surprising; handles should typically be as fast or much
faster than reflection (VarHandles can be faster than Unsafe in certain
cases), but may carry a slightly more expensive setup cost - do you have 
a reproducer I could try?

8b122 - do you mean 8u122 EA?

Thanks!

/Claes

On 2017-01-12 15:23, Stephen Colebourne wrote:
> I've recently tried [1] converting Joda-Beans use of setAccessible()
> to use MethodHandle. Since it is a code generator, the actual coding
> is relatively easy, and obtaining the MethodHandles.Lookup instance
> with the "private" capability is simple. While the MethodHandles API
> looks very complex, it isn't too bad to use, although it is
> undoubtedly more complex than reflection.
>
> (Note that the standard Joda-Beans technique is to code generate
> normal Java code to avoid the need to use reflection, but it can
> optionally generate reflection-based code in "light bean" mode. It is
> that reflection approach that is being examined here).
>
> The real problem however is performance. In my tests, I am seeing a
> MethodHandle approach being 2 to 3 times slower than a reflection
> approach for identical functionality, which is quite a significant
> degradation. (using Java 8 b122)
>
> Given the performance, I left to question whether the repeated Jigsaw
> advice to use MethodHandle instead of setAccessible is viable - in the
> kinds of places that use reflection, performance tends to be critical.
> Is there, or has there been, work in Java 9 to improve the performance
> of method handles?
>
> Stephen
>
> [1] https://github.com/JodaOrg/joda-beans/commits/wip/methodhandles
>