Trait mmtk::util::heap::GCTriggerPolicy

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pub trait GCTriggerPolicy<VM: VMBinding>: Sync + Send {
    // Required methods
    fn is_gc_required(
        &self,
        space_full: bool,
        space: Option<SpaceStats<'_, VM>>,
        plan: &dyn Plan<VM = VM>
    ) -> bool;
    fn is_heap_full(&self, plan: &dyn Plan<VM = VM>) -> bool;
    fn get_current_heap_size_in_pages(&self) -> usize;
    fn get_max_heap_size_in_pages(&self) -> usize;
    fn can_heap_size_grow(&self) -> bool;

    // Provided methods
    fn on_pending_allocation(&self, _pages: usize) { ... }
    fn on_gc_start(&self, _mmtk: &'static MMTK<VM>) { ... }
    fn on_gc_release(&self, _mmtk: &'static MMTK<VM>) { ... }
    fn on_gc_end(&self, _mmtk: &'static MMTK<VM>) { ... }
}

Expand description

This trait describes a GC trigger policy. A triggering policy have hooks to be informed about GC start/end so they can collect some statistics about GC and allocation. The policy needs to decide the (current) heap limit and decide whether a GC should be performed.

Required Methods§

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fn is_gc_required( &self, space_full: bool, space: Option<SpaceStats<'_, VM>>, plan: &dyn Plan<VM = VM> ) -> bool

Is a GC required now? The GC trigger may implement its own heuristics to decide when a GC should be performed. However, we recommend the implementation to do its own checks first, and always call plan.collection_required(space_full, space) at the end as a fallback to see if the plan needs to do a GC.

Arguments:

space_full: Is any space full?
space: The space that is full. The GC trigger may access some stats of the space.
plan: The reference to the plan in use.

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fn is_heap_full(&self, plan: &dyn Plan<VM = VM>) -> bool

Is current heap full?

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fn get_current_heap_size_in_pages(&self) -> usize

Return the current heap size (in pages)

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fn get_max_heap_size_in_pages(&self) -> usize

Return the upper bound of heap size

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fn can_heap_size_grow(&self) -> bool

Can the heap size grow?

Provided Methods§

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fn on_pending_allocation(&self, _pages: usize)

Inform the triggering policy that we have pending allocation. Any GC trigger policy with dynamic heap size should take this into account when calculating a new heap size. Failing to do so may result in unnecessay GCs, or result in an infinite loop if the new heap size can never accomodate the pending allocation.

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fn on_gc_start(&self, _mmtk: &'static MMTK<VM>)

Inform the triggering policy that a GC starts.

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fn on_gc_release(&self, _mmtk: &'static MMTK<VM>)

Inform the triggering policy that a GC is about to start the release work. This is called in the global Release work packet. This means we assume a plan do not schedule any work that reclaims memory before the global Release work. The current plans satisfy this assumption: they schedule other release work in plan.release().

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