Julia Invalidation & Compiler Profiler
Find and fix the causes of Julia compile latency — method invalidations and runtime-dispatch inference — without leaving VS Code.
Features
Invalidation & inference analysis
Julia Profiler: Analyze Invalidations & Inference runs SnoopCompile.jl on the project containing the active file:
@snoop_invalidations while loading the package → Invalidations view in the activity bar: each invalidating method with the number of compiled MethodInstances it invalidated, expandable down to the invalidated callers. Click any node to jump to its source.@snoop_inference while running a workload script (snoop/workload.jl by default; Create Inference Workload Script scaffolds it) → flame graph report: zoomable inference flame graph, top methods by self inference time and the call sites whose runtime dispatch triggered fresh inference.
SnoopCompile is installed into a private environment in the extension's storage and stacked onto LOAD_PATH, so your Project.toml/Manifest.toml are never modified. The last profile is kept per workspace; Open Profile JSON… loads a saved one.
Refactoring linter
Static checks (tree-sitter) for code patterns that commonly cause invalidations or poor inference:
| Rule |
What it flags |
Quick fix |
julia/abstract-field |
struct fields typed ::Real, ::AbstractVector, Vector{Any}, or untyped |
turn the field into a type parameter |
julia/nonconst-global |
non-const globals read inside functions |
add const |
julia/untyped-container |
[], Any[], Dict() |
— |
julia/global-in-function |
global x = … inside functions |
— |
julia/base-method-extension |
type piracy, and Base/Core methods extended with abstract/untyped arguments |
— |
When a profile is loaded, runtime-backed diagnostics mark the exact methods that invalidated code (julia/runtime-invalidation) and the call sites that triggered inference (julia/runtime-inference-trigger). Every diagnostic links to the relevant Julia manual or SnoopCompile documentation, and can be suppressed with # ide-ext-ignore-next-line <rule-id>.
Insert PrecompileTools Workload adds a @setup_workload/@compile_workload block to cache compiled code in the package image.
Benchmark comparison
Run Benchmarks & Compare… runs your PkgBenchmark-style benchmark/benchmarks.jl (const SUITE = BenchmarkGroup()) on a baseline git ref — checked out in a temporary worktree — and on the working tree, then judges median times like BenchmarkTools.judge (default tolerance 5 %). Create GitHub Actions Benchmark Workflow adds an AirspeedVelocity.jl workflow that comments the same comparison on pull requests.
Requirements
- Julia ≥ 1.10 (tested with 1.13). The binary is taken from
juliaProfiler.executablePath, then julia.executablePath (Julia extension), then PATH, then ~/.juliaup/bin/julia.
- Internet access the first time, to install SnoopCompile / BenchmarkTools into the private tool environments.
git for baseline comparisons.
Settings
| Setting |
Default |
|
juliaProfiler.executablePath |
"" |
Julia binary |
juliaProfiler.workloadScript |
"" |
workload for @snoop_inference (relative to the project) |
juliaProfiler.timeoutMinutes |
30 |
abort long analyses |
juliaProfiler.lint.enable / lint.disabledRules |
true / [] |
linter control |
juliaProfiler.invalidationThreshold |
10 |
recorded invalidations at or above this are warnings |
juliaProfiler.benchmark.seconds / benchmark.timeTolerance |
1 / 0.05 |
benchmark budget and judge tolerance |
Command line
The same features are available as jest-julia, for terminals and CI pipelines:
- Install from VS Code: Julia Profiler: Install 'jest-julia' Command in PATH. It needs no Node.js.
- Install from npm:
npm i -g @jest-test-team/security-cli.
jest-julia lint src/
jest-julia analyze --out profile.json --max-invalidated 0
jest-julia report profile.json
jest-julia lint src/ --profile profile.json # add recorded invalidations / triggers
jest-julia bench --baseline main # exit 1 on regressions
jest-julia init bench
- Reports:
--format text|json|sarif|md.
- Exit codes:
1 on findings or a failed check, so the commands work as CI gates.
- Options: see
jest-julia <command> --help.
Sources
