RFR: Encode phase for each generation separately

[Roman Kennke]

On Tue, 25 May 2021 21:05:52 GMT, William Kemper <wkemper at openjdk.org> wrote:

> This change encodes the state/activity of each generation separately for the overall collector status. There are complementary changes in [my fork of the visualizer](https://github.com/earthling-amzn/shenandoah-visualizer/tree/genshen-visualizer). There is no explicit versioning of the protocol between the encoding in the collector and the decoding in the visualizer. The change in this PR is compatible with the `genshen-visualizer` branch in my fork, but is _not_ compatible with the [upstream visualizer](https://github.com/openjdk/shenandoah-visualizer). Should I open a PR in the visualizer? Should we add a versioning scheme to the prototcol and try to maintain compatibility with older versions?

Looks good. Thanks!

If the genshen-visualizer is still compatible with upstream's Shenandoah, then please file a PR against upstream visualizer. I don't think we need versioning. It would be nice if we can maintain backwards compatibility if it's not too much trouble.

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Marked as reviewed by rkennke (Lead).

PR: https://git.openjdk.java.net/shenandoah/pull/46