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MMTk 0.17.0

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@qinsoon qinsoon released this 23 Feb 02:26
· 320 commits to master since this release
v0.17.0
0fb520a
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Learn about vigilant mode.

Plan

  • Fix a bug where SemiSpace::get_available_pages returned unused pages as 'available pages'. It should return half of the unused pages as 'available'.
  • Fix a bug where generational plans may make full-heap GC decision before all the releasing work is done. Now plans have a Plan::end_of_gc() method
    that is executed after all the GC work is done.
  • Fix a bug where generational plans tended to trigger full heap GCs when heap is full. Now we properly use Appel-style nursery and allow
    the nursery to extend to the heap size.
  • Add a feature immix_zero_on_release as a debug feature for Immix to eagerly zero any reclaimed memory.
  • Fix a bug where the alloc bits for dead objects were still set after the objects were reclaimed. Now Immix eagerly clears the alloc bits
    once the memory is reclaimed.
  • Fix a bug where Immix uses forwarding bits and forwarding pointers but did not declare it.

Allocator

  • Fix a bug about the maximum object size in FreeListAllocator. The allowed maximum object size depends on both the block size and the largest bin size.

Scheduler

  • Add a 'sentinel' mechanism to execute a specified 'sentinel' work packet when a bucket is drained, and prevent the GC from entering the next stage depending
    on the sentinel packet. This makes it possible to expand the transitive closure multiple times. It replaces GCWorkScheduler::closure_end().

API

  • Add a new set of APIs to support binding-specific weak reference processing:
    • Add Scanning::process_weak_refs() and Scanning::forward_weak_refs(). They both supply an ObjectTracerContext argument for retaining and
      updating weak references. Scanning::process_weak_refs() allows a boolean return value to indicate if the method should be called again
      by MMTk after finishing transitive closures for the weak references, which can be used to implement ephemeron.
    • Add Collection::post_forwarding() which is called by MMTk after all weak reference related work is done. A binding can use this call
      for any post processing for weak references, such as enqueue cleared weak references to a queue (Java).
    • These replace old methods for the same purpose, like Collection::process_weak_refs(), Collection::vm_release(), and memory_manager::on_closure_end.

Misc

  • Upgrade the Rust toolchain we use to 1.66.1 and upgrade MSRV to 1.61.0.
  • Improve the boot time significantly for MMTk:
    • Space descriptor map is created as an zeroed vector.
    • Mmapper coalesces the mmap requests for adjancent chunks, and reduces our mmap system calls at boot time.
  • Add GCTrigger to allow different heuristics to trigger a GC:
    • Implement FixedHeapSizeTrigger that triggers the GC when the maximum heap size is reached (the current approach).
    • Implement MemBalancerTrigger (https://dl.acm.org/doi/pdf/10.1145/3563323) as the dynamic heap resize heuristic.
  • Refactor SFTMap so it is dynamically created now.
  • Fix a bug where Address::store dropped the value after store.
  • Fix a bug about an incorrect pointer cast in unsafe code in CommonFreeListPageResource.
  • Remove all inline directives from our code base. We rely on Rust compiler and PGO for inlining decisions.
  • Remove SynchronizedCounter.
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