RFR: 8078901: Add trace event for G1 MMU information

[Erik Helin]

Hi Stefan,

sorry for not getting to this earlier, thanks a lot for this patch!

On 2015-04-30, Stefan Johansson wrote:
> Hi,
> 
> Please review this change to add a trace event for MMU tracking:
> https://bugs.openjdk.java.net/browse/JDK-8078901
> 
> Webrev:
> http://cr.openjdk.java.net/~sjohanss/8078901/hotspot.00/

I have two comments:
- instead of using multiple inheritance, can you instead have the
  G1MMUTracer as a field in G1NewTracer and G1OldTracer? Then you can
  have a getter to the field.
- in G1MMUTracer, can you have the function report_mmu not take a
  G1MMUTracker* but instead have two additional double parameters, one
  for time_slice and one for max_gc_time? This way the tracers don't
  need to know about G1MMUTracker.

Thanks!
Erik

> Summary:
> When adding pause information to the G1MMUTracker, it now reports a
> trace-event with the latest MMU information.
> 
> add_pause() previously took a bool argument that was unused, but said
> whether or not it was a concurrent-cycle pause. I removed the bool argument
> and added G1MMUTracer* argument. The G1MMUTracer is an interface that both
> the stw-tracer and the cm-tracer now implement to make sure the correct GC
> id is provided with the event.
> 
> Thanks,
> Stefan