Enum vk_mem::MemoryUsage

pub enum MemoryUsage {
    Unknown,
    GpuOnly,
    CpuOnly,
    CpuToGpu,
    GpuToCpu,
}

Intended usage of memory.

Variants

Unknown

No intended memory usage specified. Use other members of AllocationCreateInfo to specify your requirements.

GpuOnly

Memory will be used on device only, so fast access from the device is preferred. It usually means device-local GPU (video) memory. No need to be mappable on host. It is roughly equivalent of D3D12_HEAP_TYPE_DEFAULT.

Usage:

• Resources written and read by device, e.g. images used as attachments.
• Resources transferred from host once (immutable) or infrequently and read by device multiple times, e.g. textures to be sampled, vertex buffers, uniform (constant) buffers, and majority of other types of resources used on GPU.

Allocation may still end up in ash::vk::MemoryPropertyFlags::HOST_VISIBLE memory on some implementations. In such case, you are free to map it. You can use AllocationCreateFlags::MAPPED with this usage type.

CpuOnly

Memory will be mappable on host. It usually means CPU (system) memory. Guarantees to be ash::vk::MemoryPropertyFlags::HOST_VISIBLE and ash::vk::MemoryPropertyFlags::HOST_COHERENT. CPU access is typically uncached. Writes may be write-combined. Resources created in this pool may still be accessible to the device, but access to them can be slow. It is roughly equivalent of D3D12_HEAP_TYPE_UPLOAD.

Usage: Staging copy of resources used as transfer source.

CpuToGpu

Memory that is both mappable on host (guarantees to be ash::vk::MemoryPropertyFlags::HOST_VISIBLE) and preferably fast to access by GPU. CPU access is typically uncached. Writes may be write-combined.

Usage: Resources written frequently by host (dynamic), read by device. E.g. textures, vertex buffers, uniform buffers updated every frame or every draw call.

GpuToCpu

Memory mappable on host (guarantees to be ash::vk::MemoryPropertFlags::HOST_VISIBLE) and cached. It is roughly equivalent of D3D12_HEAP_TYPE_READBACK.

Usage:

• Resources written by device, read by host - results of some computations, e.g. screen capture, average scene luminance for HDR tone mapping.
• Any resources read or accessed randomly on host, e.g. CPU-side copy of vertex buffer used as source of transfer, but also used for collision detection.

Trait Implementations

impl Clone for MemoryUsage

fn clone(&self) -> MemoryUsage

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Copy for MemoryUsage

impl Debug for MemoryUsage

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

Formats the value using the given formatter.

impl Eq for MemoryUsage

impl Hash for MemoryUsage

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given [Hasher].

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given [Hasher].

impl Ord for MemoryUsage

fn cmp(&self, other: &MemoryUsage) -> Ordering

This method returns an [Ordering] between self and other.

#[must_use]fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

#[must_use]fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

#[must_use]fn clamp(self, min: Self, max: Self) -> Self

🔬 This is a nightly-only experimental API. (clamp)

Restrict a value to a certain interval.

impl PartialEq<MemoryUsage> for MemoryUsage

fn eq(&self, other: &MemoryUsage) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use]fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialOrd<MemoryUsage> for MemoryUsage

fn partial_cmp(&self, other: &MemoryUsage) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use]fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use]fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use]fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use]fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl StructuralEq for MemoryUsage

impl StructuralPartialEq for MemoryUsage