Guides
XPerf cross-language smell catalog
XPerf umbrella map: the same performance smell across kits. Rule IDs are per-kit (not shared). A YES / measured ratio on one runtime does not transfer to another — re-bench before porting advice.
| Kit | Language | Lint IDs |
|---|---|---|
| zperf | Zig | zp-alloc-hot–zp-alloc-print-hot |
| cperf | C | cp-alloc-hot–cp-struct-by-value |
| jsperf | JS/TS (V8) | jp-alloc-hot–jp-clone-per-event |
| jvmperf | Java/Kotlin | 29 active jp-* slugs, jp-boxed-primitive-collection…jp-non-static-field-updater (see its docs/rule-ids.md; ≠ jsperf) |
| goperf | Go | gp-make-hot–gp-time-now-hot |
| pyperf | Python | pp-str-plus-hot–pp-open-hot |
| swiftperf | Swift | sp-array-no-reserve, sp-print-hot, plus sp-dateformatter-hot / sp-json-decode-hot / sp-regex-hot / sp-file-read-hot / sp-clock-hot / sp-value-for-key-hot |
| arktsperf | ArkTS | at-alloc-hot–at-json-hot |
| cppperf | C++17 | cx-regex-ctor-hot, cx-endl-hot, cx-clock-hot, cx-ifstream-hot, cx-const-by-value, cx-vector-bool (string append and string-stream removed) |
| csharpperf | C# | cs-list-add-no-capacity–cs-field-by-name-hot |
| phpperf | PHP | ph-string-dot-hot–ph-echo-hot |
| rubyperf | Ruby | rb-string-plus-hot–rb-file-read-hot |
| rustperf | Rust | rs-alloc-hot–rs-clock-hot (rs-map-new-hot restored, about 1.5×) |
| kotlinperf | Kotlin | kt-list-add-hot–kt-println-hot (empty-add removed) |
| objcperf | Objective-C | oc-nsstring-append-hot / oc-nslog-hot (both off), plus oc-dateformatter-hot / oc-json-hot / oc-regex-hot / oc-file-read-hot / oc-clock-hot / oc-value-for-key-hot (array-add removed) |
| dartperf | Dart | dt-list-add-empty–dt-growable-add-empty |
| luaperf | Lua | lu-table-insert-hot–lu-print-hot |
| beamperf | Elixir + Erlang | be-list-concat-reduce–be-enum-map-filter-chain |
| nimperf | Nim | nm-seq-add-hot–nm-seq-no-capacity |
Prefix overlap: jsperf and jvmperf both use the jp- prefix, with disjoint slug sets. For example jp-boxed-primitive-collection (~5.96×) exists only in jvmperf, and jp-alloc-hot (~19×, off under the app preset) only in jsperf. Always name the kit when citing a jp-* rule.
How to read
- Pick a smell → open each kit’s rule +
packages/<kit>/evidence/<ID>.mdbefore treating a finding as a speed claim. - Evidence column cites ratios already in evidence-policy / JSONL / STATIC-VS-* — not invented here.
- Cells:
- rule id + short note = shipped lint (or guide example)
- n/a = runtime physics differ; do not force a mapping
- pending = rule or stub exists; no honest wall-clock JSONL yet
- guide = chapter / example only (no lint yet)
- Porting across languages must re-bench (roadmap-next.md §5).
- Fixture fire ≠ speed; deopt / PrintCompilation line counts ≠ escalate (rule-regression.md).
Catalog
| Smell | zperf | cperf | jsperf | jvmperf | Evidence | Notes |
|---|---|---|---|---|---|---|
| alloc-in-loop / arena / pool | zp-alloc-hot ~1.4× GPA vs arena; zp-per-packet-alloc (hot-path, shares zp-alloc-hot); zp-create-destroy-hot ~11× create/destroy vs pool; zp-fixed-size-alloc-hot ~8.5× fixed alloc(u8,N) vs pool | cp-alloc-hot ~10.8× malloc-loop vs arena (error) | jp-alloc-hot ~19× / ~6.4× new/push vs once (off under app preset — alloc/GC, not deopt) | jp-expensive-alloc-hot expensive factory in loop (hint; tiny-pool negative); jp-hot-heavy-alloc hot heavy alloc (pending ART); jp-hot-payload-copy ~15.8× frame buffer reuse (error) | z: zp-alloc-hot, zp-create-destroy-hot, zp-fixed-size-alloc-hot JSONL; c: cp-alloc-hot; js: jp-alloc-hot; jvm: jp-expensive-alloc-hot, jp-hot-payload-copy (+ jp-hot-heavy-alloc stub) | Same idea (hoist / reuse); Zig smp already cheap → prefer pool for fixed size. jvm jp-expensive-alloc-hot ≠ “always pool”. |
| buffer grow / capacity / builder | zp-append-without-reserve ~2.1× append reserve; zp-map-put-without-ensure ~2.8× map ensure; zp-shift-on-read ~17× shift-on-read vs cursor (candidate error) | cp-realloc-grow-one ~12.6× realloc+1 vs doubling (error) | jp-string-plus-in-loop (removed 2026-10-23; push+join was not ~2×); V8 arrays grow differently; prealloc appears under jp-alloc-hot good fixtures | jp-string-concat-hot ~14.2× string += vs builder (error); jp-unpresized-collection ~1.6× unpresized fill (hint PARTIAL); jp-baos-tobytearray-copy ~12.8× BAOS toByteArray vs writeTo (error) | z: zp-append-without-reserve, zp-shift-on-read, zp-map-put-without-ensure; c: cp-realloc-grow-one; jvm: jp-string-concat-hot, jp-unpresized-collection, jp-baos-tobytearray-copy | Closest cross-kit pair: cp-realloc-grow-one ↔ zp-append-without-reserve ↔ jvm jp-string-concat-hot. Not the same as JS holey. |
| hot IO / print / log / format | zp-print-hot ~6e4× print vs quiet (env I/O, not escalate); zp-unbuffered-io ~49× empty Writer vs 4KiB (candidate error) | cp-printf-hot ~4.8× unbuf/buf hot; #if 0 ~1× → off (default app preset) | jp-console-hot ~1328× console vs quiet (off app / hint engine — env) | jp-format-hot ~17× String.format hot (error); jp-log-hot ~28× unguarded log concat (error); jp-hot-format-log hot format/log (pending ART) | z: zp-print-hot, zp-unbuffered-io; c: cp-printf-hot; js: jp-console-hot; jvm: jp-format-hot, jp-log-hot (+ jp-hot-format-log stub) | Prefer buffered Io / level guards. Do not escalate env-bound print alone. |
| shape / layout / SoA / density | zp-aos-single-field ~6.6× AoS→SoA; zp-packable-bools / related density stubs (pending); zp-large-struct-by-value by-value (inconclusive -Ofast); zp-bool-array ~30× bool[] vs bitset | guide SoA examples (p01_soa.c); no CP rule | guide §04 maps / IC / polymorphic (~12× in STATIC-VS-V8); no layout JP | jp-many-boolean-fields (removed 2026-10-22; COH 16=16 no win); Kotlin layout smells elsewhere | z: zp-aos-single-field, zp-bool-array JSONL + pending stubs; extern padding removed (~1.2×); js: STATIC-VS-V8; jvm: jp-many-boolean-fields | V8 hidden classes ≠ C padding ≠ Zig extern ≠ HotSpot object header. |
| holey / sparse elements | n/a — Zig slices ≠ V8 elements kinds | n/a — C “sparse” is CSR/hash, different problem | jp-delete-array-hole ~3.2× holey delete a[i] vs packed (error); STATIC case2 ~5.5× | jp-android-sparse-array Android SparseArray (pending ART) — not V8 holey | js: jp-delete-array-hole (+ STATIC-VS-V8); jvm: jp-android-sparse-array stub only | Do not map jp-delete-array-hole → CP or ZP. Android Sparse* ≠ V8 holey. |
| delete / remove / tombstone | zp-queue-ordered-remove ~466× orderedRemove vs ring (candidate error) | n/a | jp-delete-shape ~474× delete prop (off under app preset — G3 OK-idiom demote) | n/a as V8/Zig remove; closest reuse smells are buffer/pool | js: jp-delete-shape; z: zp-queue-ordered-remove | Related cost of mid-structure delete, not the same smell (JS tombstone ≠ Zig memmove). |
| sync / lock / contested types | n/a (no ZP sync rule) | n/a | n/a | jp-legacy-synchronized-type (removed 2026-10-22; ~1.08× / HT negative) | jvm: _removed/ tombstone | Contended lock cost is workload-dependent; micro alone does not escalate. |
| boxed / value boxing / stream box | n/a (no managed boxing) | n/a | n/a (numbers are values; objects under alloc jp-alloc-hot) | jp-boxed-primitive-collection ~5.96× boxed collections (error); jp-boxed-stream ~149× boxed Stream (error); jp-value-class-boxing ~5× B/op value-class box (error) | jvm: jp-boxed-primitive-collection, jp-boxed-stream, jp-value-class-boxing; STATIC-VS-HOTSPOT | JVM-specific; jsperf has no boxing rule. |
| string / intern / concat family | n/a as JVM intern; Zig has zp-static-string-map StaticStringMap ~2.5× | n/a | n/a as intern (jp-string-plus-in-loop removed 2026-10-23; alloc cost under jp-alloc-hot) | jp-string-concat-hot concat (error); jp-string-intern-hot ~6.6× intern() in loop (error); jp-format-hot format (error) | jvm: jp-string-concat-hot, jp-format-hot, jp-string-intern-hot; z: zp-static-string-map | Overlaps hot-IO/format row for jp-format-hot; listed here for string-table / builder family. |
| regex / parse control-flow | n/a | n/a | jp-map-filter-chain (hint; 35000 rows ~4.6×–9.8×, 3-row filter+map ~1.3×) | jp-regex-hot ~1.36× regex compile in loop (hint); jp-exception-control-flow ~64× exception-as-control (error) | jvm: jp-regex-hot, jp-exception-control-flow | Weak wall for regex → stays hint; exceptions-as-flow is strong. |
| collection chain / copy / lambda alloc (Kotlin) | n/a | n/a | n/a | jp-collection-chain ~265× eager chain (off); jp-lambda-to-non-inline-hot ~244× B/op non-inline lambda (off); jp-data-copy-hot ~208× copy in loop (error); jp-lazy-default-mode lazy mode (pending) | jvm: jp-collection-chain, jp-lambda-to-non-inline-hot, jp-data-copy-hot (+ jp-lazy-default-mode stub) | Kotlin-centric; B/op often clearer than ns/op. |
| enum / map specialization | zp-static-string-map StaticStringMap ~2.5× (literal keys) | n/a | n/a | jp-enum-key-hash-collection ~2.1× EnumMap vs HashMap enum keys (error) | z: zp-static-string-map; jvm: jp-enum-key-hash-collection | Compile-time / ordinal maps — similar idea, different APIs. |
| client / updater / factory recreate | n/a | n/a | n/a | jp-client-factory-recreate ~5e5× HttpClient new vs reuse (error); jp-non-static-field-updater create ~165× / steady inc ~1.0× (hint) | jvm: jp-client-factory-recreate, jp-non-static-field-updater | Factory reuse; steady-state may be flat (jp-non-static-field-updater). |
| Android / ART device smells | n/a | n/a | n/a | jp-android-sparse-array, jp-hot-heavy-alloc–jp-ui-text-append stubs only (pending ART/device): SparseArray, hot alloc, format/log, system call, Bitmap, Handler post, UI text | jvm evidence stubs jp-android-sparse-array … jp-ui-text-append | No box JSONL until ART/device harness. |
| correctness / static-only (not speed gates) | zp-debug-allocator mode switch; zp-missing-free leak; zp-catch-unreachable-alloc catch unreachable; zp-oversized-enum-tag enum tag size — all N/A wall | — | — | jp-finalize finalize (pending design/correctness); vt-unsafe-threadlocal-pool guide-only VT/pool myth (not shipped) | z: stubs zp-debug-allocator / zp-missing-free / zp-catch-unreachable-* / zp-oversized-enum-tag; jvm: jp-finalize + vt-unsafe-threadlocal-pool | Do not invent speed JSONL for these. |
Catalog rows: 15 smell families (z/c/js/jvm) + sections for go/py/swift/arkts/cpp/csharp/php/ruby/rust/kotlin/objc/dart/lua/beam/nim. All 19 kits corpus-ready (AGENT.md G3, 2026-10-22 Asia/Shanghai) — findings remain heuristics, not guaranteed speedups.
jvmperf policy snapshot: see packages/jvmperf/docs/evidence-policy.md for current error/hint/off/pending maps (slug IDs). Guide-only: vt-unsafe-threadlocal-pool (not shipped). Removed measured-useless: jp-legacy-synchronized-type, jp-many-boolean-fields.
Newer kits
Defaults are mostly off or hint. All kits below are corpus-ready under G3. Measured JSONL exists for most rules (see rule-regression.md); nimperf has none because G4 was blocked (no toolchain). Re-bench before escalating severity.
| Smell | goperf | pyperf | swiftperf | arktsperf | Notes |
|---|---|---|---|---|---|
| alloc-in-loop / arena / pool | gp-make-hot make/new in loop (off) | n/a as make; closest pp-list-plus-rebind list growth | n/a (ARC) | at-alloc-hot object/new/push{ in loop (off) | Same idea as cp-alloc-hot / js jp-alloc-hot; ratios in each kit's evidence-policy (swift: none, G4 blocked) |
| buffer grow / string builder | gp-string-plus-hot string += (off); gp-append-nil-slice append on nil slice (hint) | pp-str-plus-hot string += (off); pp-list-plus-rebind list + rebinding (hint) | sp-array-no-reserve append without reserveCapacity (hint); string += removed (~1×, reserve slower) | (folds into at-alloc-hot) | Closest to jvm jp-string-concat-hot / cp-realloc-grow-one family |
| hot IO / print / log | gp-fmt-hot fmt.*printf in loop (off) | pp-print-hot print( (off) | sp-print-hot print( (off) | at-console-hot console.* (off) | Env-bound; not escalated |
| delete / shape | n/a | n/a | n/a | no ArkTS delete rule (removed; Node proxy ~1×) | Aligns with jsperf jp-delete-shape idea; ArkTS VM may differ |
| force-unwrap / unsafe optional | n/a | n/a | no force-unwrap rule (removed; same time as if let) | n/a | Swift-specific |
| defer / chains / lookups in loop | gp-defer-hot defer in loop (hint) | n/a | no map/joined rule (removed; about 1.2×) | at-includes-hot includes lookup (hint); at-json-hot JSON.parse/stringify (hint) | Kit-specific; no cross-kit mapping implied |
cpp / csharp / php / ruby
| Smell | cppperf | csharpperf | phpperf | rubyperf | Notes |
|---|---|---|---|---|---|
| buffer grow / capacity | removed (vector push without reserve — tombstone) | cs-list-add-no-capacity List.Add without Capacity (off) | ph-array-merge-rebind array_merge rebinding (error) | rb-array-plus-rebind Array + / concat (off). Hash#merge was removed (literal build slower and more allocating on Ruby 4.0.8) | Same idea as cp-realloc-grow-one / jvm jp-unpresized-collection; php is the only one with error (G4) |
| string builder | no C++ string-append rule (removed; ~1.1×) | cs-string-plus-hot string += (off) | ph-string-dot-hot .= (off) | rb-string-plus-hot string += (off) | Closest to jvm jp-string-concat-hot / gp-string-plus-hot |
| hot IO / print | removed (iostream in loop — tombstone) | cs-console-hot Console.Write* (off) | ph-echo-hot echo/print (hint) | rb-puts-hot puts/print (off) | Env-bound; not escalated |
| regex in loop | — | cs-regex-hot regex in loop (hint) | — | — | Closest to jvm jp-regex-hot; weak wall, stays hint |
| bounds-checked index | removed (.at() in loop — tombstone; reverse @-O2) | — | — | — | Prefer operator[] when index already validated; rule not shipped |
cppperf vs cperf: cppperf is dedicated C++17; cperf remains C11 (+ light C++).
rust / kotlin / objc / dart / lua / beam
| Smell | rustperf | kotlinperf | objcperf | dartperf | luaperf | beamperf | Notes |
|---|---|---|---|---|---|---|---|
| buffer grow / capacity | rs-alloc-hot alloc/clone (off); rs-collect-vec-hot collect-in-loop (hint); sized Vec::new plus push removed (~1× large fill) | kt-list-add-hot list alloc (off) | removed (NSMutableArray add — tombstone) | dt-list-add-empty List.add (off); dt-growable-add-empty empty growable + add (hint) | lu-table-insert-hot table.insert (off) | be-list-concat-reduce list ++ (hint); be-map-merge-hot Map.merge (hint); be-enum-map-filter-chain map-then-filter (hint) | Same idea as cp-realloc-grow-one |
| string builder | rs-format-rebind-hot format! rebind (error, ~99×); amortized += removed (~1×) | kt-string-plus-hot string += (off) | oc-nsstring-append-hot stringByAppendingString (off) | dt-string-plus-hot string + (off) | lu-string-concat-hot .. (error) | removed (<> append — tombstone; mixed/reverse) | Closest to jvm jp-string-concat-hot; Rust splits amortized vs format! |
| hot IO / print | rs-println-hot println! (hint) | kt-println-hot println (off) | oc-nslog-hot NSLog (off) | dt-print-hot print (off) | lu-print-hot print (hint) | be-io-puts-hot IO.puts / io:format (off) | Env-bound; not escalated |
kotlinperf is Kotlin-first heuristics; measured JVM/JMH evidence stays in jvmperf (do not duplicate). objcperf ≠ swiftperf. beamperf covers .ex/.exs/.erl.
nim
| Smell | nimperf | Notes |
|---|---|---|
| buffer grow / capacity | nm-seq-add-hot seq .add in loop (off after G3); nm-seq-no-capacity empty seq + .add (hint) | OK-idiom on Nim/Arraymancer/nimbus; opt-in. No JSONL (G4 blocked, no nim) |
| string builder | removed (&= / s = s & x — tombstone; join was slower) | Closest to jvm jp-string-concat-hot / rb-string-plus-hot |
| hot IO / print | nm-echo-hot echo in loop (off) | Env-bound; not escalated |
Empty / thin cells (honest)
| Gap | Why |
|---|---|
| cperf SoA lint | Guide examples only. cp-wide-bool-flags is a hint for four full-width boolean flags and is not a SoA rule |
| jsperf print mapped but severity off (app) | Measured, env-bound |
| jsperf buffer-grow dedicated rule | Covered loosely via jp-alloc-hot prealloc fixtures; jp-string-plus-in-loop was removed after the join bench missed ~2× |
| zperf sync/lock | No rule |
| Cross-kit holey outside js | Physics differ → n/a by design |
| jvm jp-android-sparse-array … jp-ui-text-append | Need ART/device |
| zperf zp-packable-bools / zp-usize-index-field / zp-optional-scalar-field density | Pending density harness |
| jvm jp-sleep-polling sleep-polling | pending — design/situational, not micro |
| vt-unsafe-threadlocal-pool | Guide-first; not in Rule.RULES |
| nimperf evidence | G4 blocked (no Nim toolchain on the measurement host); stubs only, no JSONL |
| arktsperf / objcperf evidence | Measured on proxies (Node/V8, GNUstep), not the target runtime |
| swiftperf build on Linux CI | Needs Swift toolchain; smoke skips when absent |
| csharpperf build without SDK | Needs dotnet; smoke skips when absent |
| arktsperf device benches | Prefer HarmonyOS device; Node proxy alone does not escalate |
| cppperf vs cperf overlap | Deliberate split: C++ kit separate from C11 kit |
Evidence pointers
| Kit | Policy | Correlate / batch (out of repo) |
|---|---|---|
| shared | rule-regression.md | this catalog |
| zperf | packages/zperf/docs/evidence-policy.md | packages/zperf/evidence/ |
| cperf | packages/cperf/docs/evidence-policy.md | STATIC-VS-O2 (not in repo) |
| jsperf | packages/jsperf/docs/evidence-policy.md | STATIC-VS-V8 (not in repo) |
| jvmperf | packages/jvmperf/docs/evidence-policy.md | STATIC-VS-HOTSPOT, EVIDENCE-BATCH (not in repo) |
The correlate and batch notes named above are not part of this git repository — they are listed as plain names so the GitHub UI does not 404.
Hot compile / parse / query (2026-10-23)
These slugs are hint. Fixtures are paired. There is no JSONL, and they are not part of the 2026-10-22 corpus verdict.
| Kit | Slug | Smell |
|---|---|---|
| pyperf | pp-json-hot | json.loads / dumps in loop |
| pyperf | pp-deepcopy-hot | deepcopy in loop |
| jsperf | jp-regex-ctor-hot | new RegExp (stable pattern; default scope all) |
| jsperf | jp-json-hot | JSON.parse / stringify (stable text; default scope all) |
| jsperf | jp-dom-query-hot | querySelector / getElementById (stable selector; default scope all) |
| jsperf | jp-query-all-star | querySelectorAll('*') full-tree walk (templates too) |
| jsperf | jp-execjs-in-timer | built executeJavaScript/evaluate inside timers |
| jsperf | jp-clone-per-event | structuredClone / JSON round-trip of event-like args |
| goperf | gp-regexp-compile-hot | regexp.Compile in loop |
| goperf | gp-json-marshal-hot | json.Marshal / Unmarshal in loop |
| goperf | gp-reflect-hot | reflect.TypeOf / ValueOf in loop |
| cppperf | cx-regex-ctor-hot | std::regex constructed in loop |
| cppperf | cx-endl-hot | endl flush in loop |
| csharpperf | cs-linq-materialize-hot | ToList / ToArray / ToDictionary in loop |
| csharpperf | cs-format-hot | string.Format in loop |
| rubyperf | rb-regexp-new-hot | Regexp.new in loop |
| rubyperf | rb-json-hot | JSON.parse / generate in loop |
| rustperf | rs-regex-new-hot | Regex::new in loop |
Related
- overview.md — umbrella status
- playbook.md — shared loop + regression contract
- roadmap-next.md — next fills for empty cells
- docs/README.md — docs index