JDK-8237012 : Release Note: Shenandoah arraycopy improvements
  • Type: Sub-task
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 14
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2020-01-13
  • Updated: 2020-01-13
  • Resolved: 2020-01-13
When handling Object[] arraycopy, Shenandoah used to evacuate array elements / fix references in the destination array after the copy. This is not efficient when multiple copies are done, as fixups would have to run on every copy. Plus, the fixups in the destination array do not improve the accesses to the source array.

Unfortunately, this was the only way to deal with arraycopy until the GC API was extended. In JDK 14 with GC API improvements, Shenandoah is now able to fix up object arrays at source before the arraycopy, which improves performance and opens up other optimization opportunities.