Add benchmark harness and disable ORT thread pool spinning

benchmark/CMakeLists.txt

@@ -0,0 +1,21 @@
+cmake_minimum_required(VERSION 3.16)
+project(obs-bgremoval-bench LANGUAGES CXX)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+find_package(OpenCV REQUIRED COMPONENTS core)
+find_package(Threads REQUIRED)
+find_package(onnxruntime CONFIG QUIET)
+
+add_executable(bench bench.cpp)
+target_include_directories(bench PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/../src)
+target_link_libraries(bench PRIVATE ${OpenCV_LIBS} Threads::Threads)
+
+if(onnxruntime_FOUND)
+  message(STATUS "ONNX Runtime found - CPU utilization test enabled")
+  target_compile_definitions(bench PRIVATE HAS_ONNXRUNTIME=1)
+  target_link_libraries(bench PRIVATE onnxruntime::onnxruntime)
+else()
+  message(STATUS "ONNX Runtime not found - CPU utilization test disabled")
+endif()

benchmark/README.md

@@ -0,0 +1,61 @@
+# Benchmark
+
+Micro-benchmark for the `obs-backgroundremoval` pre-inference pipeline.
+It exercises the same code path the plugin runs in `video_tick` before
+model inference: cloning the input frame and running a PSNR similarity
+check on full-size 1920x1080 BGRA frames.
+
+## Prerequisites
+
+- A **C++17** compiler
+- **CMake** 3.16+
+- **OpenCV** (core)
+- **ONNX Runtime** (optional) — enables the CPU utilisation test
+
+## Build
+
+Run from the repository root:
+
+```bash
+cmake -B build benchmark
+cmake --build build
+```
+
+If ONNX Runtime is found by CMake, the CPU utilisation test is compiled in
+automatically.
+
+## Usage
+
+```
+./build/bench [-n <frames>] [-m <model_path>]
+```
+
+| Flag | Default | Description |
+|------|---------|-------------|
+| `-n` | 660 | Number of synthetic frames to process |
+| `-m` | *(none)* | Path to an ONNX model (e.g. `benchmark/tiny.onnx`). Enables the ORT CPU utilisation test (Linux only). |
+
+## What it measures
+
+- **Per-frame timing** — mean, median, and p95 latency in microseconds.
+- **Hardware perf counters** (Linux only) — cache references, cache misses,
+  LLC store misses via `perf_event_open`.
+- **ORT CPU utilisation** (requires `-m`) — runs 90 frames at 30 fps with a
+  real ONNX Runtime session and reports wall time vs CPU time, showing the
+  effect of thread-pool spin-waiting.
+
+## Example output
+
+```
+Generated 60 synthetic frames (1920x1080 BGRA)
+
+=== obs-backgroundremoval benchmark ===
+Frames: 60 @ 1920x1080 BGRA (7.9 MB/frame)
+  mean:   2309.6 us/frame
+  median: 2012.1 us/frame
+  p95:    4637.1 us/frame
+  total:  138.6 ms (60 frames)
+  cache-misses:     29067554 (84.0% of 34591781 refs)
+  LLC-store-misses: 8461194 (86.8% of 9749379 stores)
+===
+```