JDK-8277373 : Make maximum card table size dependent on ObjectAlignmentInBytes
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 18
  • Priority: P4
  • Status: Open
  • Resolution: Unresolved
  • Submitted: 2021-11-18
  • Updated: 2021-11-19
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Related Reports
Relates :  
JDK-8272773 - Configurable card table card size
Description
JDK-8272773 introduced a configurable card size, with a maximum of up to 1024 bytes.

This limit is imposed by the BOT, where for the byte there are 7 bits available to address offsets within a card, with current (default) ObjectAlignmentInBytes of 8 (= 2^3) this means a limit of 2^10 (=1024) card size.

Try to make maximum representable BOT offset dependent on ObjectAlignmentInBytes so that with higher values for that it can be increased.

Also do some testing if this is actually useful.