Struct mmtk::policy::marksweepspace::native_ms::global::MarkSweepSpace

pub struct MarkSweepSpace<VM: VMBinding> {
    pub common: CommonSpace<VM>,
    pr: BlockPageResource<VM, Block>,
    chunk_map: ChunkMap,
    scheduler: Arc<GCWorkScheduler<VM>>,
    abandoned: Mutex<AbandonedBlockLists>,
    abandoned_in_gc: Mutex<AbandonedBlockLists>,
    pending_release_packets: AtomicUsize,
}

A mark sweep space.

The space and each free list allocator own some block lists. A block that is in use belongs to exactly one of the block lists. In this case, whoever owns a block list has exclusive access on the blocks in the list. There should be no data race to access blocks. A thread should NOT access a block list if it does not own the block list.

The table below roughly describes what we do in each phase.

Phase	Allocator local block lists	Global abandoned block lists	Chunk map
Allocation	Alloc from local	Move blocks from global to local block lists	-
	Lazy: sweep local blocks
GC - Prepare	-	-	Find used chunks, reset block mark, bzero mark bit
GC - Trace	Trace object and mark blocks.	Trace object and mark blocks.	-
	No block list access.	No block list access.
GC - Release	Lazy: Move blocks to local unswept list	Lazy: Move blocks to global unswept list	_
	Eager: Sweep local blocks	Eager: Sweep global blocks
	Both: Return local blocks to a temp global list
GC - End of GC	-	Merge the temp global lists	-

Fields

common: CommonSpace<VM>

pr: BlockPageResource<VM, Block>

chunk_map: ChunkMap

Allocation status for all chunks in MS space

scheduler: Arc<GCWorkScheduler<VM>>

Work packet scheduler

abandoned: Mutex<AbandonedBlockLists>

Abandoned blocks. If a mutator dies, all its blocks go to this abandoned block lists. We reuse blocks in these lists in the mutator phase. The space needs to do the release work for these block lists.

abandoned_in_gc: Mutex<AbandonedBlockLists>

Abandoned blocks during a GC. Each allocator finishes doing release work, and returns their local blocks to the global lists. Thus we do not need to do release work for these block lists in the space. These lists are only filled in the release phase, and will be moved to the abandoned lists above at the end of a GC.

pending_release_packets: AtomicUsize

Count the number of pending ReleaseMarkSweepSpace and ReleaseMutator work packets during the Release stage.

Implementations

impl<VM: VMBinding> MarkSweepSpace<VM>

pub fn extend_global_side_metadata_specs(_specs: &mut Vec<SideMetadataSpec>)

pub fn new(args: PlanCreateSpaceArgs<'_, VM>) -> MarkSweepSpace<VM>

fn trace_object<Q: ObjectQueue>( &self, queue: &mut Q, object: ObjectReference ) -> ObjectReference

pub fn record_new_block(&self, block: Block)

pub fn prepare(&mut self)

pub fn release(&mut self)

pub fn end_of_gc(&mut self)

pub fn release_block(&self, block: Block)

Release a block.

pub fn block_clear_metadata(&self, block: Block)

pub fn acquire_block( &self, tls: VMThread, size: usize, align: usize ) -> BlockAcquireResult

pub fn get_abandoned_block_lists(&self) -> &Mutex<AbandonedBlockLists>

pub fn get_abandoned_block_lists_in_gc(&self) -> &Mutex<AbandonedBlockLists>

pub fn release_packet_done(&self)

fn generate_sweep_tasks(&self) -> Vec<Box<dyn GCWork<VM>>>

fn recycle_blocks(&self)

Trait Implementations

impl<VM: VMBinding> PolicyTraceObject<VM> for MarkSweepSpace<VM>

fn trace_object<Q: ObjectQueue, const KIND: u8>( &self, queue: &mut Q, object: ObjectReference, _copy: Option<CopySemantics>, _worker: &mut GCWorker<VM> ) -> ObjectReference

Trace object in the policy. If the policy copies objects, we should expect copy to be a Some value.

fn may_move_objects<const KIND: u8>() -> bool

Return whether the policy moves objects.

fn post_scan_object(&self, _object: ObjectReference)

Policy-specific post-scan-object hook. It is called after scanning each object in this space.

impl<VM: VMBinding> SFT for MarkSweepSpace<VM>

fn name(&self) -> &str

The space name

fn is_live(&self, object: ObjectReference) -> bool

Is the object live, determined by the policy?

fn pin_object(&self, _object: ObjectReference) -> bool

fn unpin_object(&self, _object: ObjectReference) -> bool

fn is_object_pinned(&self, _object: ObjectReference) -> bool

fn is_movable(&self) -> bool

Is the object movable, determined by the policy? E.g. the policy is non-moving, or the object is pinned.

fn is_sane(&self) -> bool

Is the object sane? A policy should return false if there is any abnormality about object - the sanity checker will fail if an object is not sane.

fn initialize_object_metadata(&self, _object: ObjectReference, _alloc: bool)

Initialize object metadata (in the header, or in the side metadata).

fn is_mmtk_object(&self, addr: Address) -> Option<ObjectReference>

Is addr a valid object reference to an object allocated in this space? This default implementation works for all spaces that use MMTk’s mapper to allocate memory. Some spaces, like MallocSpace, use third-party libraries to allocate memory. Such spaces needs to override this method.

fn find_object_from_internal_pointer( &self, ptr: Address, max_search_bytes: usize ) -> Option<ObjectReference>

fn sft_trace_object( &self, queue: &mut VectorObjectQueue, object: ObjectReference, _worker: GCWorkerMutRef<'_> ) -> ObjectReference

Trace objects through SFT. This along with SFTProcessEdges provides an easy way for most plans to trace objects without the need to implement any plan-specific code. However, tracing objects for some policies are more complicated, and they do not provide an implementation of this method. For example, mark compact space requires trace twice in each GC. Immix has defrag trace and fast trace.

fn get_forwarded_object( &self, _object: ObjectReference ) -> Option<ObjectReference>

Get forwarding pointer if the object is forwarded.

fn is_reachable(&self, object: ObjectReference) -> bool

Is the object reachable, determined by the policy? Note: Objects in ImmortalSpace may have is_live = true but are actually unreachable.

fn is_in_space(&self, _object: ObjectReference) -> bool

Is the object managed by MMTk? For most cases, if we find the sft for an object, that means the object is in the space and managed by MMTk. However, for some spaces, like MallocSpace, we mark the entire chunk in the SFT table as a malloc space, but only some of the addresses in the space contain actual MMTk objects. So they need a further check.

impl<VM: VMBinding> Space<VM> for MarkSweepSpace<VM>

fn as_space(&self) -> &dyn Space<VM>

fn as_sft(&self) -> &(dyn SFT + Sync + 'static)

fn get_page_resource(&self) -> &dyn PageResource<VM>

fn maybe_get_page_resource_mut(&mut self) -> Option<&mut dyn PageResource<VM>>

Get a mutable reference to the underlying page resource, or None if the space does not have a page resource.

fn initialize_sft(&self, sft_map: &mut dyn SFTMap)

Initialize entires in SFT map for the space. This is called when the Space object has a non-moving address, as we will use the address to set sft. Currently after we create a boxed plan, spaces in the plan have a non-moving address.

fn common(&self) -> &CommonSpace<VM>

fn release_multiple_pages(&mut self, _start: Address)

fn enumerate_objects(&self, enumerator: &mut dyn ObjectEnumerator)

Enumerate objects in the current space.

fn will_oom_on_acquire(&self, tls: VMThread, size: usize) -> bool

A check for the obvious out-of-memory case: if the requested size is larger than the heap size, it is definitely an OOM. We would like to identify that, and allows the binding to deal with OOM. Without this check, we will attempt to allocate from the page resource. If the requested size is unrealistically large (such as usize::MAX), it breaks the assumptions of our implementation of page resource, vm map, etc. This check prevents that, and allows us to handle the OOM case. Each allocator that may request an arbitrary size should call this method before acquring memory from the space. For example, bump pointer allocator and large object allocator need to call this method. On the other hand, allocators that only allocate memory in fixed size blocks do not need to call this method. An allocator should call this method before doing any computation on the size to avoid arithmatic overflow. If we have to do computation in the allocation fastpath and overflow happens there, there is nothing we can do about it. Return a boolean to indicate if we will be out of memory, determined by the check.

fn acquire(&self, tls: VMThread, pages: usize) -> Address

fn address_in_space(&self, start: Address) -> bool

fn in_space(&self, object: ObjectReference) -> bool

fn grow_space(&self, start: Address, bytes: usize, new_chunk: bool)

This is called after we get result from page resources. The space may tap into the hook to monitor heap growth. The call is made from within the page resources’ critical region, immediately before yielding the lock.

fn ensure_mapped(&self)

Ensure this space is marked as mapped – used when the space is already mapped (e.g. for a vm image which is externally mmapped.)

fn reserved_pages(&self) -> usize

fn available_physical_pages(&self) -> usize

Return the number of physical pages available.

fn get_name(&self) -> &'static str

fn get_gc_trigger(&self) -> &GCTrigger<VM>

fn set_copy_for_sft_trace(&mut self, _semantics: Option<CopySemantics>)

What copy semantic we should use for this space if we copy objects from this space. This is only needed for plans that use SFTProcessEdges

fn verify_side_metadata_sanity( &self, side_metadata_sanity_checker: &mut SideMetadataSanity )

Ensure that the current space’s metadata context does not have any issues. Panics with a suitable message if any issue is detected. It also initialises the sanity maps which will then be used if the extreme_assertions feature is active. Internally this calls verify_metadata_context() from util::metadata::sanity

impl<VM: VMBinding> Sync for MarkSweepSpace<VM>