RFR (S): 8204082: Add indication that this is the "Last Young GC before Mixed" to logs

[Thomas Schatzl]

Hi,

On Wed, 2018-05-30 at 14:50 +0200, Thomas Schatzl wrote:
> Hi all,
> 
>   can I have reviews for this change that adds an indication about
> the "last young" gc before a mixed phase to the logs?
> 
> I.e. instead of "GC Pause (Young)", that GC is called "GC Pause (Last
> Young)".
> 
> The reason for this potentially intrusive change to log parsers is
> that in quite a few situations it is useful to be really sure what
> kind of GC is being started without needing to either add gc+ergo
> logging or restarting. This situation where I was trying to figure
> out whether the given young GC I was looking at was the young gc
> before the mixed gcs or just a young-gc because the Cleanup pause
> figured out that we do not need a mixed phase.
> 
> I am not too hung up about naming it "Last Young" in particular, but
> I really would like to have this or a similar indication that is
> generally available with minimal logging.

Alternatively we could just call it "Mixed" that does not collect any
old gen regions at this time. Later we could start gc as soon as the
pause time goal permits and add a few old gen regions.

This would probably be a little confusing to users, but at least help
diagnosing logs.

There also has been the suggestion to call it "Final Young" instead of
"Last Young".

Any comments?

Thomas

> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8204082
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8204084/webrev/
> Testing:
> hs-tier 1-3