RFR(S): 8227225: ParallelGC: add subspace transitions for young gen for gc+heap=info log lines

[Thomas Schatzl]

On Fri, 2019-07-05 at 11:06 -0700, Tony Printezis wrote:
> Hi all,
> 
> This is a follow-up to 8223575 and adds subspace info for eden and
> from space to the gc+heap=info output for ParallelGC. I also added
> the before capacity, similar to 8223575, as it can change during the
> GC (see, in fact, example below).
> 
> Before:
> 
> [11.123s][info][gc,heap      ] GC(17) PSYoungGen: 4759616K-
> >1664K(4545536K)
> [11.123s][info][gc,heap      ] GC(17) ParOldGen: 1280K-
> >1280K(1376256K)
> 
> After:
> 
> [12.133s][info][gc,heap      ] GC(25) PSYoungGen:
> 2065952K(2066432K)->1536K(1983488K) Eden: 2064384K(2064384K)-
> >0K(1981952K)
> From: 1568K(2048K)->1536K(1536K)

Note that I think this is confusing, or the "From" label should be
renamed. The second part of this heap transition actually prints the
"To" space from what I understand.

What does it print on evacuation failure?

It would be cleaner imho to print From and To space separately.

> 
> [12.133s][info][gc,heap      ] GC(25) ParOldGen:
> 1272K(1376256K)->1272K(1376256K)
> 
> http://cr.openjdk.java.net/~tonyp/8227225/webrev.0/
> 
> I have a similar change ready to go for GenCollectedHeap (Serial /
> CMS).
> I’ll see what the feedback is on this before I open that for code
> review.
> 
> A couple of notes:
> 
> - I moved the PreGCValues class to gc/shared as I’d like to re-use 
> it for the GenCollectedHeap changes too.  

It's a bit awkwards as there are non-generational GCs now, but I do not
have a better idea. Maybe somebody else has.

> - Is it worth also adding info about To space to the output?

I think so.

(Note that I did not really review this change yet, just answering
questions)

Thanks,
  Thomas

> 
> Tony
> 
> PS Should I add the gc-pending-review label to any CR I open for code
> review?

As discussed, feel free to do so, but it may or may not help. Note that
there is no need to remove that label manually: if you set your JIRA
filter to ignore already fixed/resolved issues they will not be shown
automatically (if you filter).

Once or twice a year we typically bulk-remove these labels from already
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