RFR: 8072498: Multi-thread JNI weak reference processing

[Kim Barrett]

> On Aug 8, 2018, at 10:27 AM, Kim Barrett <kim.barrett at oracle.com> wrote:
> 
>> On Aug 8, 2018, at 10:11 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
>> 
>> Hi Kim,
>> 
>> On Tue, 2018-07-31 at 15:23 -0400, Kim Barrett wrote:
>>> […]
>>> CR:
>>> https://bugs.openjdk.java.net/browse/JDK-8072498
>>> 
>>> Webrev:
>>> http://cr.openjdk.java.net/~kbarrett/8072498/open.00/
>>> 
>>> Testing:
>>> mach5 tier1-3, hs-tier4-5.
>>> 
>>> Local and mach5 testing of TestGCBasherWithG1 and TestSystemGCWithG1,
>>> with the tests modified to use a smaller non-default value of
>>> -XX:ReferencesPerThread, to examine the logging output and verify
>>> multi-threaded execution.
>>> 
>> 
>> - g1ConcurrentMark.cpp:1673: I assume that using the serial version
>> of weak processing has been used here because of logging concerns. Is
>> there an upcoming change that fixes that?
>> One could create a local instance of a WeakProcessorPhaseTimes and just
>> take the interesting total time taken from it and print it. Or just
>> print it the same way as for the young gcs - I understand this is ugly,
>> but as long as there is no other way...
>> 
>> - same for g1FullCollector.cpp:217 and g1FullGCAdjustTask:101
> 
> These are using the parallel versions.  Maybe overloading the weak_oops_do
> name with one that takes a workgang is too subtle?

To be clear, these are calling this overload:

  template<typename IsAlive, typename KeepAlive>
  weak_oops_do(WorkGang*, IsAlive*, KeepAlive*, uint log_indent)

which stack allocates a temporary WeakProcessorPhaseTimes, calls the
parallel overload taking a phasetime as the fourth argument, and then
logs the phasetime with the requested indentation.

New webrevs without the external optimization of run_task:
full: http://cr.openjdk.java.net/~kbarrett/8072498/open.01/
incr: http://cr.openjdk.java.net/~kbarrett/8072498/open.01.inc/

And still need another reviewer.