MMTk 0.15.0

GC Plans

• Generational plans now support bounded nursery size and fixed nursery size.
• Immix can be used in a non-moving variant (with no defragmentation) to facilitate early porting stages
  where a non-moving GC is expected by the VM. Enable the feature immix_no_defrag to use the variant.
  Note that this variant performs poorly, compared to normal immix.

API

• Add mod build_info for bindings to get information about the current build.
• Add trait Edge. A binding can implement its own edge type if they need more sophisiticated edges than a simple address slot,
  e.g. to support compressed pointers, base pointers with offsets, or tagged pointers.
• Add APIs for implementing write barriers. MMTk provides subusming barriers object_reference_write() and pre/post write barriers object_reference_write_pre/post().
• Add APIs for implementing barriers for memory copying such as array_copy in Java. MMTk provides memory_region_copy() (subsuming) and memory_region_copy_pre/post().
• The ignore_system_g_c option is renamed to ignore_system_gc to be consistent with our naming convention.
• The max/min_nursery option is replaced by nursery. Bindings can use nursery=Fixed:<size> or Bounded:<size> to config the nursery size.
• Metadata access methods now requires a type parameter for the metadata value.
• Metadata compare-exchange methods now return a Result rather than a boolean, which is more consistent with Rust atomic types.
• Metadata now supports fetch_and, fetch_or and fetch_update.
• Header metadata access methods in ObjectModel now have default implementations.

Misc

• Remove all stdout printing in MMTk.
• Fix a bug that CopySpace should not try zeroing alloc bit if there is no allocation in the space.
• Fix a few issues in documentation.