Struct mmtk::policy::lockfreeimmortalspace::LockFreeImmortalSpace

pub struct LockFreeImmortalSpace<VM: VMBinding> {
    name: &'static str,
    cursor: Atomic<Address>,
    limit: Address,
    start: Address,
    total_bytes: usize,
    slow_path_zeroing: bool,
    metadata: SideMetadataContext,
    gc_trigger: Arc<GCTrigger<VM>>,
}

This type implements a lock free version of the immortal collection policy. This is close to the OpenJDK’s epsilon GC. Different from the normal ImmortalSpace, this version should only be used by NoGC plan, and it now uses the whole heap range.

Fields

name: &'static str

cursor: Atomic<Address>

Heap range start

limit: Address

Heap range end

start: Address

start of this space

total_bytes: usize

Total bytes for the space

slow_path_zeroing: bool

Zero memory after slow-path allocation

metadata: SideMetadataContext

gc_trigger: Arc<GCTrigger<VM>>

Implementations

impl<VM: VMBinding> LockFreeImmortalSpace<VM>

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

Trait Implementations

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

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

Get the name of the space

We have to override the default implementation because LockFreeImmortalSpace doesn’t have a common space

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

We have to override the default implementation because LockFreeImmortalSpace doesn’t put metadata in a common space

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

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

fn release_multiple_pages(&mut self, _start: Address)

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 reserved_pages(&self) -> usize

fn acquire(&self, _tls: VMThread, pages: usize) -> 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 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 available_physical_pages(&self) -> usize

Return the number of physical pages available.

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