Enum mmtk::util::metadata::MetadataSpec

pub enum MetadataSpec {
    InHeader(HeaderMetadataSpec),
    OnSide(SideMetadataSpec),
}

This struct stores the specification of a metadata bit-set. It is used as an input to the (inline) functions provided by the side metadata module.

Each plan or policy which uses a metadata bit-set, needs to create an instance of this struct.

For performance reasons, objects of this struct should be constants.

Variants

InHeader(HeaderMetadataSpec)

In-header metadata uses bits from an object header.

OnSide(SideMetadataSpec)

On-side metadata uses a side table.

Implementations

impl MetadataSpec

pub const fn is_on_side(&self) -> bool

Is this metadata stored in the side table?

pub const fn is_in_header(&self) -> bool

Is this metadata stored in the object header?

pub const fn extract_side_spec(&self) -> &SideMetadataSpec

Extract SideMetadataSpec from a MetadataSpec. Panics if this is not side metadata.

pub unsafe fn load<VM: VMBinding, T: MetadataValue>( &self, object: ObjectReference, mask: Option<T> ) -> T

A function to non-atomically load the specified metadata’s content. Returns the metadata value.

Arguments:

• object: is a reference to the target object.
• mask: is an optional mask value for the metadata. This value is used in cases like the forwarding pointer metadata, where some of the bits are reused by other metadata such as the forwarding bits.

Safety

This is a non-atomic load, thus not thread-safe.

pub fn load_atomic<VM: VMBinding, T: MetadataValue>( &self, object: ObjectReference, mask: Option<T>, ordering: Ordering ) -> T

A function to atomically load the specified metadata’s content. Returns the metadata value.

Arguments:

• object: is a reference to the target object.
• mask: is an optional mask value for the metadata. This value is used in cases like the forwarding pointer metadata, where some of the bits are reused by other metadata such as the forwarding bits.
• atomic_ordering: is the ordering for the load operation.

pub unsafe fn store<VM: VMBinding, T: MetadataValue>( &self, object: ObjectReference, val: T, mask: Option<T> )

A function to non-atomically store a value to the specified metadata.

Arguments:

• object: is a reference to the target object.
• val: is the new metadata value to be stored.
• mask: is an optional mask value for the metadata. This value is used in cases like the forwarding pointer metadata, where some of the bits are reused by other metadata such as the forwarding bits.

Safety

This is a non-atomic store, thus not thread-safe.

pub fn store_atomic<VM: VMBinding, T: MetadataValue>( &self, object: ObjectReference, val: T, mask: Option<T>, ordering: Ordering )

A function to atomically store a value to the specified metadata.

Arguments:

• object: is a reference to the target object.
• val: is the new metadata value to be stored.
• mask: is an optional mask value for the metadata. This value is used in cases like the forwarding pointer metadata, where some of the bits are reused by other metadata such as the forwarding bits.
• ordering: is the ordering for the store operation.

pub fn compare_exchange_metadata<VM: VMBinding, T: MetadataValue>( &self, object: ObjectReference, old_val: T, new_val: T, mask: Option<T>, success_order: Ordering, failure_order: Ordering ) -> Result<T, T>

A function to atomically compare-and-exchange the specified metadata’s content. Returns true if the operation is successful, and false otherwise.

Arguments:

• object: is a reference to the target object.
• old_val: is the expected current value of the metadata.
• new_val: is the new metadata value to be stored if the compare-and-exchange operation is successful.
• mask: is an optional mask value for the metadata. This value is used in cases like the forwarding pointer metadata, where some of the bits are reused by other metadata such as the forwarding bits.
• success_order: is the atomic ordering used if the operation is successful.
• failure_order: is the atomic ordering used if the operation fails.

pub fn fetch_add_metadata<VM: VMBinding, T: MetadataValue>( &self, object: ObjectReference, val: T, order: Ordering ) -> T

A function to atomically perform an add operation on the specified metadata’s content. Returns the old metadata value.

Arguments:

• object: is a reference to the target object.
• val: is the value to be added to the current value of the metadata.
• order: is the atomic ordering of the fetch-and-add operation.

pub fn fetch_sub_metadata<VM: VMBinding, T: MetadataValue>( &self, object: ObjectReference, val: T, order: Ordering ) -> T

A function to atomically perform a subtract operation on the specified metadata’s content. Returns the old metadata value.

Arguments:

• object: is a reference to the target object.
• val: is the value to be subtracted from the current value of the metadata.
• order: is the atomic ordering of the fetch-and-add operation.

pub fn fetch_and_metadata<VM: VMBinding, T: MetadataValue>( &self, object: ObjectReference, val: T, order: Ordering ) -> T

A function to atomically perform a bit-and operation on the specified metadata’s content. Returns the old metadata value.

Arguments:

• object: is a reference to the target object.
• val: is the value to bit-and with the current value of the metadata.
• order: is the atomic ordering of the fetch-and-add operation.

pub fn fetch_or_metadata<VM: VMBinding, T: MetadataValue>( &self, object: ObjectReference, val: T, order: Ordering ) -> T

A function to atomically perform a bit-or operation on the specified metadata’s content. Returns the old metadata value.

Arguments:

• object: is a reference to the target object.
• val: is the value to bit-or with the current value of the metadata.
• order: is the atomic ordering of the fetch-and-add operation.

pub fn fetch_update_metadata<VM: VMBinding, T: MetadataValue, F: FnMut(T) -> Option<T> + Copy>( &self, object: ObjectReference, set_order: Ordering, fetch_order: Ordering, f: F ) -> Result<T, T>

A function to atomically perform an update operation on the specified metadata’s content. The semantics are the same as Rust’s fetch_update on atomic types. Returns a Result of Ok(previous_value) if the function returned Some(_), else Err(previous_value).

Arguments:

• object: is a reference to the target object.
• val: is the value to bit-or with the current value of the metadata.
• order: is the atomic ordering of the fetch-and-add operation.
• f: the update function. The function may be called multiple times.

Trait Implementations

impl Clone for MetadataSpec

fn clone(&self) -> MetadataSpec

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for MetadataSpec

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Copy for MetadataSpec