perf: add 4 CodSpeed scenarios for cold-start work (issue #557)#12
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Each scenario maps 1:1 to a planned cold-start improvement so a per- PR CodSpeed delta is unambiguous. Without these, the wins from the upcoming PRs would be invisible to the dashboard. * XA-3 — attribute_walk_jvm_java_lang_System 1 000 walks of `gateway.jvm.java.lang.System`. Each walk re-issues 3 reflection round-trips because JVMView / JavaPackage / JavaClass __getattr__ don't memoize today. Cache canary for the upcoming Python attribute-cache PR — should collapse to ~0 round-trips after first walk once memoization lands. * XB — gateway_reconnect_against_running_jvm 50 fresh JavaGateway() instances against the fixture JVM. Measures per-connection setup cost: Java accept() loop allocates 14 command class instances per connection (GatewayConnection.java:196-208), Python runs _create_connection + socket setup. Lever for the Java-side command-prototype-cache PR. * XC — callback_infra_overhead_unused X1-1 workload (10 000 currentTimeMillis() calls) with CallbackServer started but no callbacks invoked. Delta vs X1-1 is the steady-state overhead of running the callback server alongside the main gateway. Target of the lazy-CallbackClient PR. * XD — full_cold_start_subprocess_first_call subprocess.Popen -> first call -> shutdown, one cycle per round. Slow per-iteration (~350 ms on M-series + JDK 21, multi-second on slower hosts); CodSpeed adapts iteration count. Target of the JVM-flag opt-ins (TieredStopAtLevel=1, AppCDS, CRaC). Implementation notes: XA / XB / XC follow the existing MacroScenario contract and run through the macro_gateway fixture in codspeed_macros.py (shared JVM, setup once, measure many). XD owns its JVM lifecycle inside measure() — it must NOT share the fresh_jvm()-managed fixture because both default to port 25333. So XD is registered in a new _COLD_START_SCENARIOS list parametrized through a new test_cold_start_scenario function. XD is also omitted from ALL_MACRO_CLASSES so the framework runner doesn't try to share its JVM either. Local measurements on M-series + JDK 21 (Temurin 21.0.10): XA-3: ~94 ms / 1000 walks = 94 us per walk (3 RTTs each) XB: ~21 ms / 50 reconnects = 425 us per reconnect XC: ~236 ms / 10k calls = 23.6 us per call XD: ~355 ms per full cold-start cycle Co-authored-by: Isaac
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The XD ``test_cold_start_scenario`` introduced in #12 used a blind ``time.sleep(0.25)`` followed by a direct ``JavaGateway()`` connect attempt. On CodSpeed CI runners (and any host slower than a modern laptop) the JVM hadn't yet bound its listen socket when the connect fired, surfacing as ``ConnectionRefusedError: [Errno 111] Connection refused`` and failing the whole codspeed workflow. Switch XD's body to the existing ``fresh_jvm`` context manager with ``readiness_retries=5``. ``fresh_jvm`` polls connection readiness with ``check_connection`` and only proceeds once the JVM is actually accepting calls — same convention the rest of the test suite uses. This also drops a bunch of try/finally boilerplate since ``fresh_jvm`` handles spawn/shutdown. Locally on M-series + JDK 21: XD median ~355 ms (unchanged from post-#12 baseline). The variance is higher in cold-start measurement by nature; what matters is the elimination of hard failures on slower hosts. Co-authored-by: Isaac
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#557) (#595) Adds four CodSpeed scenarios mapping 1:1 to py4j cold-start improvement work areas, plus tightens the perf-framework JVM readiness check so slow scenarios get enough samples per benchmark budget. Pure measurement infrastructure — zero behavior change in py4j proper. Touches only the perf testing subtree. New scenarios: * XA-3 — attribute_walk_jvm_java_lang_System 1 000 walks of ``gateway.jvm.java.lang.System``. Each walk re-issues 3 reflection round-trips today because JVMView / JavaPackage / JavaClass __getattr__ don't memoize. Cache canary for the upcoming Python attribute-cache PR. * XB — gateway_reconnect_against_running_jvm 50 fresh ``JavaGateway()`` against the fixture JVM per round. Measures per-connection setup cost — Java accept() loop allocates 14 command class instances per connection (GatewayConnection.java:196-208), Python runs _create_connection + socket setup. * XC — callback_infra_overhead_unused X1-1 workload with ``CallbackServer`` started, but no callbacks actually invoked. Delta vs X1-1 = the steady-state cost of running callback infrastructure alongside the main gateway. * XD — full_cold_start_subprocess_first_call subprocess.Popen -> first call -> shutdown, one cycle per round. Slow per-iteration; CodSpeed adapts iteration count. Target of the JVM-flag work (AppCDS, -XX:TieredStopAtLevel=1, CRaC). XA/XB/XC share the long-running fixture JVM (``test_macro_scenario``). XD owns its full JVM lifecycle inside ``measure()`` and is dispatched via a separate ``test_cold_start_scenario`` test function — it can't share the fixture because both default to port 25333. Readiness model overhaul in ``perf.jvm.fresh_jvm``: before: 0.25 s sleep + 1 retry x 2.0 s = 2.25 s ceiling after: 0 s sleep + 300 retries x 0.05 s = 15 s ceiling Tight polling matters for XD on CodSpeed: under the old model each XD iteration cost ~2.7 s and CodSpeed could fit only one sample per benchmark budget, making variance and regression detection impossible. Under the new model XD per-iteration finishes in ~500-1100 ms — enough for 2-5 samples per budget. The unconditional 0.25 s startup_sleep's original rationale ("let the OS reuse the listen port") no longer applies: GatewayServer.startSocket() already uses SO_REUSEADDR, so bind() succeeds immediately even over TIME_WAIT. Backwards compatibility preserved — callers can pass ``startup_sleep=0.25`` to restore the old wait pattern. Validated on byteoak#12, #13, #16 (where these changes originated as 3 iterative PRs; bundled here for a clean single upstream review surface). Full 56-cell CI matrix green on each byteoak iteration. CodSpeed scenarios surface real cold-start work on subsequent PRs — issue #557. Co-authored-by: Isaac
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Summary
Adds 4 CodSpeed scenarios so the planned cold-start improvement PRs (per upstream issue py4j/py4j#557) each get an unambiguous per-PR delta on the dashboard. Pure measurement infra — zero behavior change in py4j itself.
Each scenario maps 1:1 to a planned PR:
gateway.jvm.java.lang.System. Each walk re-issues 3 reflection round-trips today becauseJVMView/JavaPackage/JavaClass.__getattr__don't memoize. Should collapse to ~0 RTTs after the first walk once memoization lands.JavaGateway()instances against a running JVM. Measures per-connection setup cost — Java accept loop allocates 14 command class instances per connection (GatewayConnection.java:196-208).CallbackClientPRcurrentTimeMillis()calls) withCallbackServerstarted but no callbacks invoked. Delta vs X1-1 = steady-state overhead of the callback infrastructure.-XX:TieredStopAtLevel=1, AppCDS, CRaC)subprocess.Popen→ first call → shutdown, one cycle per round. Full cold start.Local measurements (M-series + JDK 21 / Temurin 21.0.10)
Implementation notes
MacroScenariocontract and reuse themacro_gatewayfixture incodspeed_macros.py(shared JVM, setup once, measure many).measure()— it must NOT share thefresh_jvm()-managed fixture because both default to port 25333. So XD is registered in a new_COLD_START_SCENARIOSlist parametrized through a newtest_cold_start_scenariofunction, and is omitted fromALL_MACRO_CLASSESso the framework runner doesn't try to share its JVM either.Test plan
python -m py4j.tests.perf --only XA-3,XB,XCpasses through the framework runner