youknowone · Aug 30, 2026 · Aug 30, 2026
diff --git a/.github/workflows/codspeed.yaml b/.github/workflows/codspeed.yaml
@@ -0,0 +1,77 @@
+on:
+  push:
+    branches: [main]
+  pull_request:
+    types: [unlabeled, opened, synchronize, reopened]
+  merge_group:
+  # `workflow_dispatch` allows CodSpeed to trigger backtest
+  # performance analysis in order to generate initial data.
+  workflow_dispatch:
+
+name: CodSpeed
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref_name }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: true
+
+env:
+  CARGO_INCREMENTAL: 0
+  CARGO_TERM_COLOR: always
+  CI: true
+
+jobs:
+  benchmarks:
+    if: ${{ !contains(github.event.pull_request.labels.*.name, 'skip:ci') }}
+    name: Run benchmarks
+    runs-on: ubuntu-latest
+    timeout-minutes: 90
+    permissions:
+      contents: read
+      id-token: write # for OpenID Connect authentication with CodSpeed
+    env:
+      CACHE_PATHS: |
+        ~/.cargo/bin/
+        ~/.cargo/registry/index/
+        ~/.cargo/registry/cache/
+        ~/.cargo/git/db/
+        target/
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+
+      - uses: dtolnay/rust-toolchain@stable
+
+      # The benchmarks are linked against libpython through the pyo3 dev-dependency.
+      - uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
+
+      - name: Restore cache
+        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+        with:
+          path: ${{ env.CACHE_PATHS }}
+          key: codspeed-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: codspeed-
+        continue-on-error: true
+
+      - name: Install cargo-codspeed
+        run: cargo install cargo-codspeed --locked --version ^5
+
+      - name: Build the benchmark targets
+        run: cargo codspeed build --locked --measurement-mode simulation -p rustpython -p rustpython-sre_engine
+
+      - name: Save cache
+        if: ${{ github.ref == 'refs/heads/main' }} # only save on main
+        uses: actions/cache/save@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+        with:
+          path: ${{ env.CACHE_PATHS }}
+          key: codspeed-${{ hashFiles('**/Cargo.lock') }}
+        continue-on-error: true
+
+      - name: Run the benchmarks
+        uses: CodSpeedHQ/action@373d6868929f444bc08d901fd0eb0ad52a8875ea # v5.2.1
+        with:
+          mode: simulation
+          run: cargo codspeed run -p rustpython -p rustpython-sre_engine
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
@@ -206,7 +206,7 @@ cranelift = "0.132.0"
 cranelift-jit = "0.132.0"
 cranelift-module = "0.132.0"
 crc32fast = "1.3.2"
-criterion = { version = "0.8", features = ["html_reports"] }
+criterion = { package = "codspeed-criterion-compat", version = "5.0.1", features = ["html_reports"] }
 crossbeam-utils = "0.8.21"
 csv-core = "0.1.11"
 digest = "0.11"

diff --git a/README.md b/README.md
@@ -7,6 +7,7 @@ A Python-3 (CPython >= 3.14.0) Interpreter written in Rust :snake: :scream:
 
 [![Build Status](https://github.com/RustPython/RustPython/workflows/CI/badge.svg)](https://github.com/RustPython/RustPython/actions?query=workflow%3ACI)
 [![codecov](https://codecov.io/gh/RustPython/RustPython/branch/main/graph/badge.svg)](https://codecov.io/gh/RustPython/RustPython)
+[![CodSpeed](https://img.shields.io/endpoint?url=https://codspeed.io/badge.json)](https://app.codspeed.io/RustPython/RustPython?utm_source=badge)
 [![License: MIT](https://img.shields.io/badge/License-MIT-green.svg)](https://opensource.org/licenses/MIT)
 [![Contributors](https://img.shields.io/github/contributors/RustPython/RustPython.svg)](https://github.com/RustPython/RustPython/graphs/contributors)
 [![Discord Shield](https://discordapp.com/api/guilds/1043121930691149845/widget.png?style=shield)][discord]

diff --git a/benches/README.md b/benches/README.md
@@ -21,6 +21,31 @@ specific installed Python version by running:
 PYTHON_SYS_EXECUTABLE=python3.13 cargo bench
 ```
 
+## Continuous benchmarking with CodSpeed
+
+The benchmarks are also run on every pull request by
+[CodSpeed](https://app.codspeed.io/RustPython/RustPython), which measures them with CPU simulation
+instead of wall time. `criterion` is aliased to `codspeed-criterion-compat`, so nothing changes for
+`cargo bench`: the compatibility layer only takes over when the CodSpeed runner drives the
+benchmarks.
+
+To reproduce a CodSpeed run locally, install [`cargo-codspeed`](https://crates.io/crates/cargo-codspeed)
+and the [CodSpeed CLI](https://codspeed.io/docs/cli), then run:
+
+```shell
+cargo codspeed build -p rustpython -p rustpython-sre_engine
+codspeed run --mode simulation -- cargo codspeed run -p rustpython -p rustpython-sre_engine
+```
+
+Two things differ when the benchmarks run under CodSpeed:
+
+- The CPython comparison benchmarks are skipped. They are useful to compare RustPython against
+  CPython locally, but CodSpeed tracks the evolution of RustPython itself, and running them would
+  double the duration of an already slow instrumented run.
+- The microbenchmarks using `ITERATIONS` run with a single value instead of five. The criterion
+  benchmark id does not include the iteration count, so all five sizes are reported under the same
+  name.
+
 ### Adding a benchmark
 
 Simply adding a file to the `benchmarks/` directory will add it to the set of files benchmarked. Each file is tested