Add information regarding synchronous compilations in javacore

[dev-koan]

Added a struct in J9JITConfig to store information regarding synchronous compilations and print them in javacore file.

Signed-off-by: Dev Agarwal dev.agarwal@ibm.com

[mpirvu]

We have one decision to make: do we want to measure the times needed for synchronous compilations to be performed or the waiting time of application threads? there could be several application threads waiting for the same compilation to finish.

[mpirvu]

LGTM. Please post an example of the output.

[mpirvu]

Also, please squash the 4 commits into 1.

[dev-koan]

LGTM. Please post an example of the output.

[amicic]

We have one decision to make: do we want to measure the times needed for synchronous compilations to be performed or the waiting time of application threads? there could be several application threads waiting for the same compilation to finish.

Ideally, i'd like to see each app thread maintain its own longest wait time (and associated info). For brevity, only threads that have wait times longer than a certain threshold (like 3ms or 10ms) should be reported it to javacore.

[mpirvu]

If each thread maintains the name of the sync method, with long method names and many threads there could be some footprint increase. I like the idea of applying some filtering and not include quick compilations.

[mpirvu]

@amicic To clarify: each app thread that is subject to a wait due to a synchronous compilation will have a dynamically allocated string in J9VMThread struct (to hold the name of the method it waited for). This string needs to be freed when the thread is destroyed.
Caveat: if the thread gets destroyed before the javacore generation happen, the wait info will be lost.