On 04/24/2013 08:58 AM, Peter Levart wrote:
In your revisions, you optimize for 0-interface and 1-interface proxy
class. What I hacked up earlier was just to use Class<?>[] as the
key (need to make a copy of the array to prevent that being mutated
during runtime) that is a simpler and straightforward
implementation. I didn't measure the footprint and compare the
performance of your versions. *Have you seen any performance
difference which led you to make the recent changes?*
I developed two different approaches:
1. Key made of WeakReference-s to interface Class objects.
Strong points:
- no key aliasing, validation can be pushed entirely to slow-path
- quick and scalable
- less memory usage than original code for 0 and 1-interface proxies
That's the sole reason for optimized: WekaReferece<Class> ->
WeakReference<Class> -> ... -> WeakReference<Class> linked list instead
of the WeakReference<Class>[] array approach. And it's not using any
recursion for equals/hashCode, so the peformance is comparable to array
approach and it doesn't suffer from StackOverflowExceptions for lots of
interfaces.
Weak points:
- more memory usage for 2+ -interface proxies
Latest webrev:
http://dl.dropboxusercontent.com/u/101777488/jdk8-tl/proxy-wc-wi/webrev.02/index.html
Comments:
I like this one. If 2+ -interface proxies are relatively rare and
you don't mind extra space consumption for them, I would go with this
approach.
2. Key made of interned Strings (names of interfaces)
Strong points:
- quick and scalable
- much less memory usage than original code for all variations of
interface counts and in particular for 0, 1 and 2-interface proxies
The special-cased keys for 1 and 2-interface proxies (the most frequent)
make for additional space savings.
Weak points:
- key is aliased, so the validation of interfaces has to be done - I
tried to do it post-festum with intf.isAssignableFrom(proxyClass) but
you say that is not reliable. If the validation is performed on
fast-path before proxy class is obtained, using Class.forName, the
slow-down is huge.
Latest webrev:
http://dl.dropboxusercontent.com/u/101777488/jdk8-tl/proxy-wc/webrev.03/index.html
Comments:
This is the best space-saving approach. With tricks for single and
two-interface keys, the savings are noticable.
Regards, Peter
