Enum ExecutionPath 

#[non_exhaustive]
pub enum ExecutionPath {
    NotRun,
    ZeroCopy,
    HostCopyElided,
    DeviceLocalCopy {
        copies: u8,
        reason: Option<&'static str>,
    },
    BrowserGpuCopy,
    CacheHit,
    CpuBounceFallback {
        reason: &'static str,
    },
}

Which path a frame went down. Carried on per-call result types (an interop layer’s import / export results) rather than process-global cells.

The reason in CpuBounceFallback is a &'static str deliberately — no allocation, no formatting, and CI can assert specific strings without string-slicing the whole output.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

NotRun

No run has completed yet — the initial state of a freshly-constructed processor’s metrics. Distinct from every “work happened” path so a caller can tell “no measurement yet” apart from “ran, took the CPU-bounce path”. A metrics record’s default reports this; it never appears after a completed run.

ZeroCopy

The source resource was aliased into a wgpu::Texture / wgpu::Buffer without any host or device-to-device copy on this frame.

HostCopyElided

A host-side full-buffer copy was elided: the consumer referenced the producer’s existing CPU allocation (a refcount bump) instead of memcpy-ing the payload into its own buffer. No GPU resource was aliased and no device was involved at all.

Deliberately NOT Self::ZeroCopy, which asserts a GPU aliasing import — conflating the two makes a pure-software path read as GPU zero-copy in every matrix report. Deliberately NOT Self::CpuBounceFallback either: no host memcpy ran, so it is not a bounce.

Reported by software-encode input paths that take a new reference to a decoded frame’s existing CPU planes instead of copying them into the encoder’s input frame.

DeviceLocalCopy

Zero-copy modulo a GPU-side staging copy (e.g. the wgpu-GL OES→2D blit, or a D3D11→D3D12 row-major stage). copies counts how many on-device copies happened: 1 for the “single staging copy” case; 2+ for forced bounce-and-rewrap. Distinguished from ZeroCopy so callers gating on “no driver-side copy at all” don’t conflate them, and from CpuBounceFallback because the staging cost is GPU-side.

reason is an optional &'static str tag — same no-alloc, CI-assertable rule as CpuBounceFallback::reason — naming the specific GPU-local route that ran (e.g. which bonded CUDA→GPU path), for diagnostics. None when the path has no finer label worth pinning. It does not participate in the “how much work happened” signal — copies does — but it is part of the variant’s Eq/Hash, so two DeviceLocalCopys with the same copies but different reason compare unequal.

Fields

copies: u8

reason: Option<&'static str>

BrowserGpuCopy

Web only. The operation went through a browser API that is a copy at the spec surface (copyExternalImageToTexture, new VideoFrame(canvas)) executed inside the browser — typically GPU-to-GPU, but unobservable and uncountable from wasm.

Distinct from Self::DeviceLocalCopy (which asserts a counted, known copy on a device the caller controls) and from Self::CpuBounceFallback (no CPU memcpy ran on the caller’s hot path). An option that silences cross-backend CPU-bounce warnings should never silence this — it is the expected default on the web and exists for visibility, not noise.

CacheHit

A prior import (any path) was reused this frame from the import cache; no work happened in this call. Distinct from ZeroCopy because the original import may have been a CPU upload — a caller gating “is this frame zero-copy aliased?” must not conflate the two.

CpuBounceFallback

A CPU host memcpy ran on the per-frame hot path. The reason disambiguates which call site flipped the path so a once-per- reason bounce logger can warn exactly once per cause.

Fields

reason: &'static str

Trait Implementations

impl Clone for ExecutionPath

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ExecutionPath

impl Debug for ExecutionPath

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

Formats the value using the given formatter.

impl Eq for ExecutionPath

impl Hash for ExecutionPath

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, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for ExecutionPath

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

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for ExecutionPath