2.2.6
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o File lock deletion is retried on failure, fixing an issue with file lock
  release on Windows

2.2.1
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o Page cache read performance improvements
o Page cache flush performance improvements by ordering individual pages so that
  the mapped files are written sequentially on disk

2.2.0
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o Added automatic, continuous background flushing to the PageCache.
o Made the PageCache manage its own background threads
o Made PageSwappers gracefully handle interrupts in force()
