RFR: 8339695: GenShen: Concurrent reset performance has regressed [v2]

[William Kemper]

> A misguided optimization inadvertently increased the time to perform the concurrent reset phase of the GC cycle. This "optimization" has been reverted and the time for the phase has returned to normal.

William Kemper has updated the pull request incrementally with one additional commit since the last revision:

  Fix formatting

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Changes:
  - all: https://git.openjdk.org/shenandoah/pull/495/files
  - new: https://git.openjdk.org/shenandoah/pull/495/files/bd14ca61..9c9215f4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=shenandoah&pr=495&range=01
 - incr: https://webrevs.openjdk.org/?repo=shenandoah&pr=495&range=00-01

  Stats: 10 lines in 1 file changed: 0 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/shenandoah/pull/495.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/495/head:pull/495

PR: https://git.openjdk.org/shenandoah/pull/495