RFR: CODETOOLS-7902964: jcstress: Introduce short-stride checkpointing for more frequent collisions [v2]

[Aleksey Shipilev]

> Currently, the harness uses larger strides to run and consume the results of the test. Unfortunately, when actor threads are unbalanced (e.g. run asymmetric workloads), there is a single collision per entire stride. Having shorter strides would increase collision ratios, but would create much more overhead for creating/consuming benchmark results and state.
> 
> We can do long "epoch" with several shorter "strides" and spin-loop checkpointing between strides, so that threads can catch up more often.

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Make more sensible stride{Size,Count} options

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Changes:
  - all: https://git.openjdk.java.net/jcstress/pull/69/files
  - new: https://git.openjdk.java.net/jcstress/pull/69/files/4db3194f..f908c592

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jcstress&pr=69&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jcstress&pr=69&range=00-01

  Stats: 55 lines in 5 files changed: 6 ins; 6 del; 43 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/69.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/69/head:pull/69

PR: https://git.openjdk.java.net/jcstress/pull/69