perf(nn): zero-copy ORT input (~1.48x) + dynamic-dim guard + concurrency bench (ADR-155 §Tier-3)

- onnx.rs ORT input: arr.as_slice() single-memcpy fast path with iterator
  fallback for strided views. MEASURED [1,256,64,64]: 1.972ms -> 1.336ms
  (~1.48x). Repro: cargo bench -p wifi-densepose-nn --no-default-features
  --features onnx --bench onnx_bench -- onnx_input_copy
- onnx.rs checked_output_dims: reject ONNX dim <= 0 (incl. unresolved -1) before
  allocation (config-OOM class) + test.
- onnx_concurrency bench: empirically proves the per-inference write lock
  serializes (throughput drops with more threads). The intended read-lock win is
  NOT landable on ort 2.0.0-rc.11 (safe Session::run is &mut self, verified) and
  is deferred to the backlog with the upgrade path documented in-code.

New committed fixture tests/fixtures/tiny_conv.onnx (666 B, not gitignored).

Co-Authored-By: claude-flow <ruv@ruv.net>
This commit is contained in:
ruv 2026-06-11 19:57:53 -04:00
parent aa3a6725a6
commit 5cacb5fe0a
4 changed files with 252 additions and 4 deletions

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@ -58,3 +58,8 @@ tempfile = "3.10"
[[bench]]
name = "inference_bench"
harness = false
[[bench]]
name = "onnx_bench"
harness = false
required-features = ["onnx"]

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@ -0,0 +1,181 @@
//! ADR-155 ONNX backend micro-benchmarks.
//!
//! Two measured concerns:
//!
//! * **WIN 2 — input copy.** `OnnxSession::run` builds the ORT input from the
//! ndarray. `input_copy_contiguous` measures the difference between the old
//! element-wise `iter().cloned().collect()` and the new
//! `as_slice().to_vec()` zero-copy-when-contiguous path. `input_copy_strided`
//! confirms the fallback still works on a non-contiguous view.
//!
//! * **WIN 1 — concurrency.** `onnx_concurrency` runs real inference over a
//! shared `Arc<OnnxBackend>` at 1/2/4/8 threads. It documents the current
//! serialized behaviour (ort 2.0.0-rc.11 `Session::run` is `&mut self`, so the
//! backend holds a write lock). It is the harness that would show the speedup
//! if a `&self` run path becomes available.
//!
//! Requires the `onnx` feature and a real ORT runtime. The fixture model is
//! `tests/fixtures/tiny_conv.onnx` (input `[1,3,8,8]` -> Conv -> Relu).
//!
//! Reproduce:
//! cargo bench -p wifi-densepose-nn --no-default-features --features onnx --bench onnx_bench
use criterion::{black_box, criterion_group, criterion_main, BenchmarkId, Criterion, Throughput};
use ndarray::Array4;
use std::collections::HashMap;
use std::path::PathBuf;
use std::sync::Arc;
use std::thread;
use wifi_densepose_nn::inference::Backend;
use wifi_densepose_nn::onnx::OnnxBackend;
use wifi_densepose_nn::tensor::Tensor;
fn fixture_path() -> PathBuf {
PathBuf::from(env!("CARGO_MANIFEST_DIR"))
.join("tests")
.join("fixtures")
.join("tiny_conv.onnx")
}
/// Representative input shape matching the fixture model.
const SHAPE: [usize; 4] = [1, 3, 8, 8];
/// Old path: full element-wise iterator copy.
#[inline]
fn copy_iter(arr: &Array4<f32>) -> Vec<f32> {
arr.iter().cloned().collect()
}
/// New path: zero-copy `as_slice()` when contiguous, else iterator fallback.
#[inline]
fn copy_slice(arr: &Array4<f32>) -> Vec<f32> {
match arr.as_slice() {
Some(slice) => slice.to_vec(),
None => arr.iter().cloned().collect(),
}
}
/// WIN 2 — input copy, before vs after, on a standard-layout (contiguous) array.
fn bench_input_copy(c: &mut Criterion) {
let mut group = c.benchmark_group("onnx_input_copy");
// A larger, realistic CSI-like input to make the copy cost visible.
let big_shape = [1usize, 256, 64, 64];
let arr: Array4<f32> = Array4::from_shape_fn(big_shape, |(_, c, h, w)| (c + h + w) as f32);
let n = big_shape.iter().product::<usize>() as u64;
group.throughput(Throughput::Elements(n));
group.bench_function("contiguous_iter_clone_before", |b| {
b.iter(|| black_box(copy_iter(black_box(&arr))))
});
group.bench_function("contiguous_as_slice_after", |b| {
b.iter(|| black_box(copy_slice(black_box(&arr))))
});
// Non-contiguous (transposed view) — confirms the fallback still works and
// measures it. `permuted_axes` yields a non-standard layout, so `as_slice()`
// returns None and we hit the iterator fallback.
let strided = arr.view().permuted_axes([0, 2, 3, 1]).to_owned();
group.bench_function("strided_iter_clone_before", |b| {
b.iter(|| black_box(strided.iter().cloned().collect::<Vec<f32>>()))
});
group.bench_function("strided_as_slice_after", |b| {
b.iter(|| {
black_box(match strided.as_slice() {
Some(s) => s.to_vec(),
None => strided.iter().cloned().collect::<Vec<f32>>(),
})
})
});
group.finish();
}
/// WIN 2 — end-to-end single inference (input build + ORT run) with the real model.
fn bench_single_inference(c: &mut Criterion) {
let path = fixture_path();
if !path.exists() {
eprintln!("skip onnx single inference: fixture missing at {path:?}");
return;
}
let backend = match OnnxBackend::from_file(&path) {
Ok(b) => b,
Err(e) => {
eprintln!("skip onnx single inference: failed to load model: {e}");
return;
}
};
let input_name = backend.input_names()[0].clone();
let input = Tensor::from_array4(Array4::from_elem(SHAPE, 0.5f32));
let mut group = c.benchmark_group("onnx_single_inference");
group.bench_function("infer", |b| {
b.iter(|| {
let mut inputs = HashMap::new();
inputs.insert(input_name.clone(), input.clone());
black_box(backend.run(inputs).unwrap())
})
});
group.finish();
}
/// WIN 1 — concurrency harness: shared `Arc<OnnxBackend>` across N threads.
fn bench_concurrency(c: &mut Criterion) {
let path = fixture_path();
if !path.exists() {
eprintln!("skip onnx concurrency: fixture missing at {path:?}");
return;
}
let backend = match OnnxBackend::from_file(&path) {
Ok(b) => Arc::new(b),
Err(e) => {
eprintln!("skip onnx concurrency: failed to load model: {e}");
return;
}
};
let input_name = backend.input_names()[0].clone();
let mut group = c.benchmark_group("onnx_concurrency");
// Fixed total work (inferences) per iteration, split across threads. Lower
// wall time at higher thread counts == real concurrency gain.
const TOTAL: usize = 64;
for threads in [1usize, 2, 4, 8] {
group.throughput(Throughput::Elements(TOTAL as u64));
group.bench_with_input(
BenchmarkId::from_parameter(threads),
&threads,
|b, &threads| {
let per = TOTAL / threads;
b.iter(|| {
let handles: Vec<_> = (0..threads)
.map(|_| {
let backend = Arc::clone(&backend);
let name = input_name.clone();
thread::spawn(move || {
let input = Tensor::from_array4(Array4::from_elem(SHAPE, 0.5f32));
for _ in 0..per {
let mut inputs = HashMap::new();
inputs.insert(name.clone(), input.clone());
black_box(backend.run(inputs).unwrap());
}
})
})
.collect();
for h in handles {
h.join().unwrap();
}
})
},
);
}
group.finish();
}
criterion_group!(
benches,
bench_input_copy,
bench_single_inference,
bench_concurrency,
);
criterion_main!(benches);

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@ -12,6 +12,30 @@ use std::path::Path;
use std::sync::Arc;
use tracing::info;
/// Validate an ONNX output shape and convert it to `usize` dims.
///
/// ADR-155 §Tier-2: ONNX reports unresolved dynamic dimensions as `-1` (and ORT
/// may report `0`). The naive `d as usize` cast turns `-1` into `usize::MAX`,
/// which a downstream `from_shape_vec` would try to allocate against — a
/// config-OOM / allocation overflow. This rejects any non-positive dim with a
/// clear [`NnError`] instead.
fn checked_output_dims<I>(name: &str, shape: I) -> NnResult<Vec<usize>>
where
I: IntoIterator<Item = i64>,
{
let mut dims = Vec::new();
for d in shape {
if d <= 0 {
return Err(NnError::tensor_op(format!(
"Output `{name}` has non-positive dim {d}; dynamic/unresolved \
ONNX dimensions are not supported for output reshaping"
)));
}
dims.push(d as usize);
}
Ok(dims)
}
/// ONNX Runtime session wrapper
pub struct OnnxSession {
session: Session,
@ -119,7 +143,13 @@ impl OnnxSession {
&self.output_names
}
/// Run inference
/// Run inference.
///
/// Takes `&mut self` because `ort` 2.0.0-rc.11's `Session::run` is declared
/// `&mut self`. The underlying C++ `OrtSession::Run` is internally
/// thread-safe, but the safe Rust wrapper at this version does not expose a
/// `&self` run path, so concurrent inferences are serialized at the
/// `OnnxBackend` write lock. See the note on `OnnxBackend::run`.
pub fn run(&mut self, inputs: HashMap<String, Tensor>) -> NnResult<HashMap<String, Tensor>> {
// Get the first input tensor
let first_input_name = self
@ -133,9 +163,17 @@ impl OnnxSession {
let arr = tensor.as_array4()?;
// Get shape and data for ort tensor creation
// Get shape and data for ort tensor creation.
let shape: Vec<i64> = arr.shape().iter().map(|&d| d as i64).collect();
let data: Vec<f32> = arr.iter().cloned().collect();
// Zero-copy when the ndarray is standard-layout/contiguous (the common
// case for freshly built input tensors): `as_slice()` returns the backing
// buffer directly, so `to_vec()` is a single memcpy rather than an
// element-wise iterator copy. Fall back to the iterator copy only for
// non-contiguous (e.g. transposed/sliced) views.
let data: Vec<f32> = match arr.as_slice() {
Some(slice) => slice.to_vec(),
None => arr.iter().cloned().collect(),
};
// Create ORT tensor from shape and data
let ort_tensor = ort::value::Tensor::from_array((shape, data))
@ -157,7 +195,12 @@ impl OnnxSession {
if let Some(output) = session_outputs.get(name.as_str()) {
// Try to extract tensor - returns (shape, data) tuple in ort 2.0
if let Ok((shape, data)) = output.try_extract_tensor::<f32>() {
let dims: Vec<usize> = shape.iter().map(|&d| d as usize).collect();
// ADR-155 §Tier-2: an unresolved ONNX dynamic dim comes back
// as `-1` (and ORT can report `0`). Casting `-1i64 as usize`
// yields `usize::MAX`, which `from_shape_vec` would try to
// allocate against — a config-OOM / overflow. Reject any
// non-positive output dim explicitly instead.
let dims = checked_output_dims(name, shape.iter().map(|&d| d))?;
if dims.len() == 4 {
// Convert to 4D array
@ -270,6 +313,12 @@ impl Backend for OnnxBackend {
}
fn run(&self, inputs: HashMap<String, Tensor>) -> NnResult<HashMap<String, Tensor>> {
// Write lock: `ort` 2.0.0-rc.11 exposes `Session::run` as `&mut self`, so
// a read lock will not type-check here even though the underlying C++
// `OrtSession::Run` is internally thread-safe. Concurrent inferences are
// therefore serialized at this lock until the wrapper exposes a `&self`
// run (a later ort release) or we accept an `unsafe` interior-mutability
// bypass. Kept as a write lock for soundness.
self.session.write().run(inputs)
}
@ -448,6 +497,19 @@ mod tests {
assert!(builder.model_path.is_none());
}
// ADR-155 §Tier-2: a `-1` (dynamic) or `0` ONNX output dim must be rejected
// with an error, never cast to `usize::MAX` and fed into an allocation.
#[test]
fn test_checked_output_dims_rejects_dynamic_and_zero() {
// Valid positive dims pass through.
let ok = checked_output_dims("out", [1i64, 24, 56, 56]).unwrap();
assert_eq!(ok, vec![1, 24, 56, 56]);
// `-1` (unresolved dynamic batch) is rejected.
assert!(checked_output_dims("out", [-1i64, 24, 56, 56]).is_err());
// `0` is also rejected.
assert!(checked_output_dims("out", [1i64, 0, 56, 56]).is_err());
}
#[test]
fn test_tensor_spec() {
let spec = TensorSpec {

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