David,
Many thanks for trialling this so promptly!
Do you have any suggestions for what instrumentation you would like to
see accompany this?
David
On 11/12/2012 1:41 PM, David M. Lloyd wrote:
On 12/10/2012 06:36 PM, David Holmes wrote:
On 10/12/2012 11:53 PM, David M. Lloyd wrote:
On 12/09/2012 10:03 PM, David Holmes wrote:
That sounds promising. Are you in a position to try out this
proposal on
a testbed with your app server?
Sure, I'd love to. What tree should I build?
Please apply the patches from the webrevs here:
http://cr.openjdk.java.net/~dholmes/concurrent-loaders/webrev.hotspot/
http://cr.openjdk.java.net/~dholmes/concurrent-loaders/webrev.jdk/
They should apply to a jdk8 or tl forest. (And I hope I didn't mess
something up generating the webrev ;-) )
Well, I've just gotten everything working and done some cursory testing
on a startup of an "empty" JBoss AS 7 instance, and then reviewing the
metrics reported by our class loader. Our timing metrics are not really
great for general-purpose benchmarking (for various uninteresting
reasons), but I can at least get enough information to know everything
is working more or less as expected:
On JDK 6 with our "unsafe" lockless modification, we're typically
loading 4707 classes, and I'm seeing anywhere from 0 to 5 define races
that were automatically resolved.
On JDK 7 using the standard registerAsParallelCapable() mechanism, we
are loading 4711 classes and I'm seeing 35-50 define races that were
automatically resolved - the overhead of locking starts to come to the
fore I think.
On JDK 8 with your patches, we are loading around 4750 classes and there
are, as expected, 0 define races (I believe, however, that we're getting
a false count though whenever defineClass() returns an already-defined
class - it would be nice if there were *some* way to detect that this
happened).
On our class loader implementations, I'm initializing this way:
static {
try {
ClassLoader.registerAsFullyConcurrent();
} catch (Throwable ignored) {
try {
ClassLoader.registerAsParallelCapable();
} catch (Throwable ignored2) {
}
}
}
The debugging message confirms that our class loaders are successfully
registered as fully concurrent, and the fact that it doesn't hang or
crash on JDK 7 indicates that they are still properly being registered
as parallel-capable on that platform.
