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8344951: Stabilize write barrier micro-benchmarks

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Reviewed-by: kvn, tschatzl
This commit is contained in:
Roberto Castañeda Lozano 2024-12-18 07:50:37 +00:00
parent 842f801c84
commit edbd76c624
1 changed files with 32 additions and 16 deletions
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48
test/micro/org/openjdk/bench/vm/compiler/WriteBarrier.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2014, 2024, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -24,6 +24,7 @@ package org.openjdk.bench.vm.compiler;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.CompilerControl;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
@ -42,7 +43,7 @@ import java.util.concurrent.TimeUnit;
@Warmup(iterations = 4, time = 2, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 4, time = 2, timeUnit = TimeUnit.SECONDS)
@Fork(value = 3)
public class WriteBarrier {
public abstract class WriteBarrier {
// For array references
public static final int NUM_REFERENCES_SMALL = 32;
@ -50,15 +51,14 @@ public class WriteBarrier {
// For array update tests
private Object[] theArraySmall;
private Object[] realReferencesSmall;
private Object[] nullReferencesSmall;
private int[] indicesSmall;
private Object[] theArrayLarge;
private Object[] realReferencesLarge;
private Object[] nullReferencesLarge;
private int[] indicesLarge;
private Object nullRef;
private Object realRef;
// For field update tests
public Referencer head = null;
public Referencer tail = null;
@ -84,13 +84,9 @@ public class WriteBarrier {
@Setup
public void setup() {
theArraySmall = new Object[NUM_REFERENCES_SMALL];
realReferencesSmall = new Object[NUM_REFERENCES_SMALL];
nullReferencesSmall = new Object[NUM_REFERENCES_SMALL];
indicesSmall = new int[NUM_REFERENCES_SMALL];
theArrayLarge = new Object[NUM_REFERENCES_LARGE];
realReferencesLarge = new Object[NUM_REFERENCES_LARGE];
nullReferencesLarge = new Object[NUM_REFERENCES_LARGE];
indicesLarge = new int[NUM_REFERENCES_LARGE];
m_w = (int) System.currentTimeMillis();
@ -99,14 +95,14 @@ public class WriteBarrier {
for (int i = 0; i < NUM_REFERENCES_SMALL; i++) {
indicesSmall[i] = get_random() % (NUM_REFERENCES_SMALL - 1);
realReferencesSmall[i] = new Object();
}
for (int i = 0; i < NUM_REFERENCES_LARGE; i++) {
indicesLarge[i] = get_random() % (NUM_REFERENCES_LARGE - 1);
realReferencesLarge[i] = new Object();
}
realRef = new Object();
// Build a small linked structure
this.head = new Referencer();
this.tail = new Referencer();
@ -124,31 +120,40 @@ public class WriteBarrier {
return Math.abs((m_z << 16) + m_w); /* 32-bit result */
}
// This and the other testArrayWriteBarrierFast benchmarks below should not
// be inlined into the JMH-generated harness method. If the methods were
// inlined, we might spill in the main loop (on x64) depending on very
// subtle conditions (such as whether LinuxPerfAsmProfiler is enabled!),
// which could distort the results.
@Benchmark
@CompilerControl(CompilerControl.Mode.DONT_INLINE)
public void testArrayWriteBarrierFastPathRealSmall() {
for (int i = 0; i < NUM_REFERENCES_SMALL; i++) {
theArraySmall[indicesSmall[NUM_REFERENCES_SMALL - i - 1]] = realReferencesSmall[indicesSmall[i]];
theArraySmall[indicesSmall[NUM_REFERENCES_SMALL - i - 1]] = realRef;
}
}
@Benchmark
@CompilerControl(CompilerControl.Mode.DONT_INLINE)
public void testArrayWriteBarrierFastPathNullSmall() {
for (int i = 0; i < NUM_REFERENCES_SMALL; i++) {
theArraySmall[indicesSmall[NUM_REFERENCES_SMALL - i - 1]] = nullReferencesSmall[indicesSmall[i]];
theArraySmall[indicesSmall[NUM_REFERENCES_SMALL - i - 1]] = nullRef;
}
}
@Benchmark
@CompilerControl(CompilerControl.Mode.DONT_INLINE)
public void testArrayWriteBarrierFastPathRealLarge() {
for (int i = 0; i < NUM_REFERENCES_LARGE; i++) {
theArrayLarge[indicesLarge[NUM_REFERENCES_LARGE - i - 1]] = realReferencesLarge[indicesLarge[i]];
theArrayLarge[indicesLarge[NUM_REFERENCES_LARGE - i - 1]] = realRef;
}
}
@Benchmark
@CompilerControl(CompilerControl.Mode.DONT_INLINE)
public void testArrayWriteBarrierFastPathNullLarge() {
for (int i = 0; i < NUM_REFERENCES_LARGE; i++) {
theArrayLarge[indicesLarge[NUM_REFERENCES_LARGE - i - 1]] = nullReferencesLarge[indicesLarge[i]];
theArrayLarge[indicesLarge[NUM_REFERENCES_LARGE - i - 1]] = nullRef;
}
}
@ -160,4 +165,15 @@ public class WriteBarrier {
this.head.append(this.tail);
this.tail.clear();
}
// This run is useful to compare different GC barrier models without being
// affected by C2 unrolling the main loop differently for each model.
@Fork(value = 3, jvmArgs = {"-XX:LoopUnrollLimit=1"})
public static class WithoutUnrolling extends WriteBarrier {}
// This run is useful to study the interaction of GC barriers and loop
// unrolling. Check that the main loop in the testArray benchmarks is
// unrolled (or not) as expected for the studied GC barrier model.
@Fork(value = 3)
public static class WithDefaultUnrolling extends WriteBarrier {}
}