Reduce virtual-thread context-propagation overhead on park/unpark #11893
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| package testdog.trace.instrumentation.java.lang.jdk21; | ||
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| import datadog.trace.junit.utils.config.WithConfig; | ||
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| /** | ||
| * Runs the {@link VirtualThreadApiInstrumentationTest} cases with the legacy context manager | ||
| * disabled, so {@code VirtualThreadState} takes the swap path instead of seed-once. Forked because | ||
| * the legacy-context-manager choice is captured once per JVM. | ||
| */ | ||
| @WithConfig(key = "legacy.context-manager.enabled", value = "false") | ||
| class VirtualThreadApiInstrumentationForkedTest extends VirtualThreadApiInstrumentationTest {} |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,185 @@ | ||
| package datadog.trace.core; | ||
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| import static java.util.concurrent.TimeUnit.MICROSECONDS; | ||
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| import datadog.context.Context; | ||
| import datadog.trace.api.EndpointTracker; | ||
| import datadog.trace.api.Stateful; | ||
| import datadog.trace.api.profiling.ProfilingContextAttribute; | ||
| import datadog.trace.api.profiling.ProfilingScope; | ||
| import datadog.trace.api.profiling.Timer.TimerType; | ||
| import datadog.trace.api.profiling.Timing; | ||
| import datadog.trace.bootstrap.instrumentation.api.AgentSpan; | ||
| import datadog.trace.bootstrap.instrumentation.api.ProfilerContext; | ||
| import datadog.trace.bootstrap.instrumentation.api.ProfilingContextIntegration; | ||
| import datadog.trace.core.monitor.HealthMetrics; | ||
| import datadog.trace.core.scopemanager.ContinuableScopeManager; | ||
| import org.openjdk.jmh.annotations.Benchmark; | ||
| import org.openjdk.jmh.annotations.BenchmarkMode; | ||
| import org.openjdk.jmh.annotations.Fork; | ||
| import org.openjdk.jmh.annotations.Level; | ||
| import org.openjdk.jmh.annotations.Measurement; | ||
| import org.openjdk.jmh.annotations.Mode; | ||
| import org.openjdk.jmh.annotations.OutputTimeUnit; | ||
| import org.openjdk.jmh.annotations.Scope; | ||
| import org.openjdk.jmh.annotations.Setup; | ||
| import org.openjdk.jmh.annotations.State; | ||
| import org.openjdk.jmh.annotations.TearDown; | ||
| import org.openjdk.jmh.annotations.Threads; | ||
| import org.openjdk.jmh.annotations.Warmup; | ||
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| /** | ||
| * Per park/unpark cost of virtual-thread context propagation: the current full {@link | ||
| * ContinuableScopeManager#swap(Context)} on every mount/unmount versus the proposed seed-once path | ||
| * (nothing when profiling is off, a profiler rebind/unbind when it is on). ddprof's native {@code | ||
| * setContext} is modelled by a stub {@link ProfilingContextIntegration} whose {@link Stateful} | ||
| * writes four volatile longs and allocates nothing. | ||
| * | ||
| * <pre> | ||
| * {@code ./gradlew :dd-trace-core:jmh -Pjmh.includes=VirtualThreadContextBenchmark -PtestJvm=21 -Pjmh.profilers=gc} | ||
| * </pre> | ||
| * | ||
| * <p>Sample run (JDK 21.0.9, {@code @Threads(8)}; run-to-run variance is high, the alloc/op figures | ||
| * are stable): | ||
| * | ||
| * <pre>{@code | ||
| * Benchmark Mode Cnt Score Error Units | ||
| * currentCycle_profilingOff thrpt 5 463.841 ± 251.726 ops/us | ||
| * currentCycle_profilingOff:gc.alloc.rate.norm thrpt 5 176.002 ± 0.016 B/op | ||
| * currentCycle_profilingOn thrpt 5 272.253 ± 21.041 ops/us | ||
| * currentCycle_profilingOn:gc.alloc.rate.norm thrpt 5 288.003 ± 0.022 B/op | ||
| * proposedSteady_profilingOff thrpt 5 5010.376 ± 354.716 ops/us | ||
| * proposedSteady_profilingOff:gc.alloc.rate.norm thrpt 5 ~0 B/op | ||
| * proposedRebindUnbind_profilingOn thrpt 5 1755.815 ± 473.954 ops/us | ||
| * proposedRebindUnbind_profilingOn:gc.alloc.rate.norm thrpt 5 ~0 B/op | ||
| * }</pre> | ||
| */ | ||
| @State(Scope.Benchmark) | ||
| @Warmup(iterations = 3, time = 1) | ||
| @Measurement(iterations = 5, time = 1) | ||
| @BenchmarkMode(Mode.Throughput) | ||
| @Threads(8) | ||
| @OutputTimeUnit(MICROSECONDS) | ||
| @Fork(value = 1) | ||
| public class VirtualThreadContextBenchmark { | ||
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| static final CoreTracer TRACER = CoreTracer.builder().build(); | ||
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| ContinuableScopeManager plainManager; // profiling off | ||
| ContinuableScopeManager profiledManager; // profiling on | ||
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| @Setup | ||
| public void setup() { | ||
| plainManager = new ContinuableScopeManager(0, false); | ||
| profiledManager = | ||
| new ContinuableScopeManager(0, false, new StubProfiling(), HealthMetrics.NO_OP); | ||
| } | ||
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| @State(Scope.Thread) | ||
| public static class ThreadState { | ||
| AgentSpan span; | ||
| Context spanContext; | ||
| Stateful profilerState; | ||
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| @Setup(Level.Trial) | ||
| public void setup(VirtualThreadContextBenchmark bench) { | ||
| span = TRACER.startSpan("benchmark", "vt"); | ||
| spanContext = span; | ||
| profilerState = new StubProfiling().newScopeState((ProfilerContext) span.spanContext()); | ||
| } | ||
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| @TearDown(Level.Trial) | ||
| public void tearDown() { | ||
| span.finish(); | ||
| } | ||
| } | ||
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| @Benchmark | ||
| public void currentCycle_profilingOff(ThreadState t) { | ||
| Context previous = plainManager.swap(t.spanContext); | ||
| plainManager.swap(previous); | ||
| } | ||
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| @Benchmark | ||
| public void currentCycle_profilingOn(ThreadState t) { | ||
| Context previous = profiledManager.swap(t.spanContext); | ||
| profiledManager.swap(previous); | ||
| } | ||
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| // current() is the faithful upper bound for the seed-once steady state (a scope-stack read). | ||
| @Benchmark | ||
| public Context proposedSteady_profilingOff(ThreadState t) { | ||
| return plainManager.current(); | ||
| } | ||
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| @Benchmark | ||
| public Context proposedRebindUnbind_profilingOn(ThreadState t) { | ||
| Context active = profiledManager.current(); | ||
| t.profilerState.activate(t.span.spanContext()); | ||
| t.profilerState.close(); | ||
| return active; | ||
| } | ||
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| static final class StubProfiling implements ProfilingContextIntegration { | ||
| @Override | ||
| public Stateful newScopeState(ProfilerContext profilerContext) { | ||
| // Per-scope storage mirrors ddprof's per-OS-thread native slots, avoiding the cross-thread | ||
| // cache contention a single shared instance would introduce. | ||
| return new StubState(); | ||
| } | ||
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| @Override | ||
| public String name() { | ||
| return "stub"; | ||
| } | ||
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| @Override | ||
| public ProfilingContextAttribute createContextAttribute(String attribute) { | ||
| return ProfilingContextAttribute.NoOp.INSTANCE; | ||
| } | ||
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| @Override | ||
| public ProfilingScope newScope() { | ||
| return ProfilingScope.NO_OP; | ||
| } | ||
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| @Override | ||
| public void onRootSpanFinished(AgentSpan rootSpan, EndpointTracker tracker) {} | ||
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| @Override | ||
| public EndpointTracker onRootSpanStarted(AgentSpan rootSpan) { | ||
| return EndpointTracker.NO_OP; | ||
| } | ||
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| @Override | ||
| public Timing start(TimerType type) { | ||
| return Timing.NoOp.INSTANCE; | ||
| } | ||
| } | ||
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| static final class StubState implements Stateful { | ||
| volatile long rootSpanId; | ||
| volatile long spanId; | ||
| volatile long traceHigh; | ||
| volatile long traceLow; | ||
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| @Override | ||
| public void activate(Object context) { | ||
| if (context instanceof ProfilerContext) { | ||
| ProfilerContext c = (ProfilerContext) context; | ||
| rootSpanId = c.getRootSpanId(); | ||
| spanId = c.getSpanId(); | ||
| traceHigh = c.getTraceIdHigh(); | ||
| traceLow = c.getTraceIdLow(); | ||
| } | ||
| } | ||
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| @Override | ||
| public void close() { | ||
| rootSpanId = 0; | ||
| spanId = 0; | ||
| traceHigh = 0; | ||
| traceLow = 0; | ||
| } | ||
| } | ||
| } |
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🔍 nitpick: That was useful to me to keep things organized compared to the other
State🥲