Struct VMLayout

pub struct VMLayout {
    pub log_address_space: usize,
    pub heap_start: Address,
    pub heap_end: Address,
    pub log_space_extent: usize,
    pub force_use_contiguous_spaces: bool,
}

Runtime-initialized virtual memory constants

Fields

log_address_space: usize

log_2 of the addressable heap virtual space.

heap_start: Address

Lowest virtual address used by the virtual machine. Should be chunk aligned.

heap_end: Address

Highest virtual address used by the virtual machine. Should be chunk aligned.

log_space_extent: usize

An upper bound on the extent of any space in the current memory layout

force_use_contiguous_spaces: bool

Should mmtk enable contiguous spaces and virtual memory for all spaces? For normal 64-bit config, this should be set to true. Each space should own a contiguous piece of virtual memory. For 32-bit or 64-bit compressed heap, we don’t have enough virtual memory, so this should be set to false.

Implementations

impl VMLayout

pub const LOG_ARCH_ADDRESS_SPACE: usize = 47usize

The maximum virtual memory address space that can be used on the target.

pub const fn max_space_extent(&self) -> usize

An upper bound on the extent of any space in the current memory layout

pub const fn available_start(&self) -> Address

Lowest virtual address available for MMTk to manage.

pub const fn available_end(&self) -> Address

Highest virtual address available for MMTk to manage.

pub const fn available_bytes(&self) -> usize

Size of the address space available to the MMTk heap.

pub const fn max_chunks(&self) -> usize

Maximum number of chunks we need to track. Only used in 32-bit layout.

pub const fn log_max_chunks(&self) -> usize

log_2 of the maximum number of chunks we need to track. Only used in 32-bit layout.

pub(crate) fn space_shift_64(&self) -> usize

Number of bits to shift a space index into/out of a virtual address. In a 32-bit model, use a dummy value so that the compiler doesn’t barf.

pub(crate) fn space_mask_64(&self) -> usize

Bitwise mask to isolate a space index in a virtual address. We can’t express this constant in a 32-bit environment, hence the conditional definition.

pub(crate) fn space_size_64(&self) -> usize

Size of each space in the 64-bit memory layout We can’t express this constant in a 32-bit environment, hence the conditional definition. FIXME: When Compiling for 32 bits this expression makes no sense

pub(crate) fn log_pages_in_space64(&self) -> usize

log_2 of the number of pages in a 64-bit space

pub(crate) fn pages_in_space64(&self) -> usize

The number of pages in a 64-bit space

pub(crate) fn address_mask(&self) -> usize

This mask extracts a few bits from address, and use it as index to the space map table. When masked with this constant, the index is 1 to 16. If we mask any arbitrary address with this mask, we will get 0 to 31 (32 entries).

const fn validate(&self)

impl VMLayout

pub const fn new_32bit() -> Self

Normal 32-bit configuration

pub const fn new_64bit() -> Self

Normal 64-bit configuration

pub(crate) fn set_custom_vm_layout(constants: VMLayout)

Custom VM layout constants. VM bindings may use this function for compressed or 39-bit heap support. This function must be called before MMTk::new()

Trait Implementations

impl Clone for VMLayout

fn clone(&self) -> VMLayout

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for VMLayout

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

Formats the value using the given formatter.

impl Default for VMLayout

fn default() -> Self

Returns the “default value” for a type.