RFR: Clear cards for old regions when they are put into service

Wed Feb 23 22:15:32 UTC 2022

Preemptively clearing cards during recycle for every region adds considerable overhead to the concurrent clean up phase. Moving card clearing transfers the cost of card clearing to the evacuation phase and reduces the cost to only those regions that will be used by the old generation.

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Commit messages:
 - Remove vestigial instrumentation
 - Only clear cards for regions that transition from free to old

Changes: https://git.openjdk.java.net/shenandoah/pull/119/files
 Webrev: https://webrevs.openjdk.java.net/?repo=shenandoah&pr=119&range=00
  Stats: 14 lines in 2 files changed: 2 ins; 4 del; 8 mod
  Patch: https://git.openjdk.java.net/shenandoah/pull/119.diff
  Fetch: git fetch https://git.openjdk.java.net/shenandoah pull/119/head:pull/119

PR: https://git.openjdk.java.net/shenandoah/pull/119