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Adaptive GC policy improvements and option for retaining aligned chunks. #3791

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Merged
merged 17 commits into from
Oct 6, 2021
Merged

Adaptive GC policy improvements and option for retaining aligned chunks. #3791

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c15cf59
Change GC policy help text to reflect actual default
zakkak Sep 20, 2021
007c8bc
Align down when adjusting for footprint to avoid getting stuck with r…
peter-hofer Sep 14, 2021
cad9466
Consider heap verification part of GC cost and ignore estimator at hi…
peter-hofer Sep 14, 2021
d88fe29
Make policies use -R:CollectYoungGenerationSeparately directly.
peter-hofer Sep 16, 2021
2a9ecc6
Use estimator slope to less hesitantly expand spaces.
peter-hofer Sep 17, 2021
3748712
Minor improvements.
peter-hofer Sep 17, 2021
7f54b29
Exclude GC safepoint from mutator time.
peter-hofer Sep 17, 2021
837b01d
Scavenge young generation during a full collection following an incre…
peter-hofer Sep 18, 2021
a82982f
Start heap at a small size, regardless of physical memory size.
peter-hofer Sep 18, 2021
b035ab0
Increase minimum space size.
peter-hofer Sep 18, 2021
670b13e
Decide whether to use estimator based on young/old cost and not total…
peter-hofer Sep 19, 2021
2bc0aee
Introduce option to limit free memory reserved for allocations.
peter-hofer Sep 22, 2021
255e22d
Adjust adaptive policy parameters.
peter-hofer Sep 25, 2021
46db6d5
Ensure that the maximum heap size is strictly less than specified (un…
peter-hofer Sep 27, 2021
68b7a07
Ignore threads reporting a fatal error during GC.
peter-hofer Sep 28, 2021
289b356
Update heap sizes after a relevant runtime option value changes.
peter-hofer Sep 30, 2021
7af0e63
Default to adaptive GC policy.
peter-hofer Sep 13, 2021
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52 changes: 28 additions & 24 deletions ...le.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/AbstractCollectionPolicy.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,8 @@
import java.util.concurrent.locks.ReentrantLock;

import org.graalvm.compiler.api.replacements.Fold;
import org.graalvm.nativeimage.Platform;
import org.graalvm.nativeimage.Platforms;
import org.graalvm.word.UnsignedWord;
import org.graalvm.word.WordFactory;

Expand All @@ -42,8 +44,10 @@

abstract class AbstractCollectionPolicy implements CollectionPolicy {

protected static final int MIN_SPACE_SIZE_IN_ALIGNED_CHUNKS = 8;
protected static final int MAX_TENURING_THRESHOLD = 15;

@Platforms(Platform.HOSTED_ONLY.class)
static int getMaxSurvivorSpaces(Integer userValue) {
assert userValue == null || userValue >= 0;
return (userValue != null) ? userValue : AbstractCollectionPolicy.MAX_TENURING_THRESHOLD;
Expand All @@ -66,7 +70,6 @@ static int getMaxSurvivorSpaces(Integer userValue) {
protected static final int NEW_RATIO = 2; // HotSpot: -XX:NewRatio
protected static final int LARGE_MEMORY_MAX_HEAP_PERCENT = 25; // -XX:MaxRAMPercentage
protected static final int SMALL_MEMORY_MAX_HEAP_PERCENT = 50; // -XX:MinRAMPercentage
protected static final double INITIAL_HEAP_MEMORY_PERCENT = 1.5625; // -XX:InitialRAMPercentage

protected final AdaptiveWeightedAverage avgYoungGenAlignedChunkFraction = new AdaptiveWeightedAverage(DEFAULT_TIME_WEIGHT);

Expand All @@ -93,23 +96,28 @@ public boolean shouldCollectOnAllocation() {
}

@Fold
static UnsignedWord minSpaceSize() {
static UnsignedWord getAlignment() {
return HeapParameters.getAlignedHeapChunkSize();
}

@Uninterruptible(reason = "Used in uninterruptible code.", mayBeInlined = true)
static UnsignedWord alignUp(UnsignedWord size) {
return UnsignedUtils.roundUp(size, minSpaceSize());
return UnsignedUtils.roundUp(size, getAlignment());
}

@Uninterruptible(reason = "Used in uninterruptible code.", mayBeInlined = true)
static UnsignedWord alignDown(UnsignedWord size) {
return UnsignedUtils.roundDown(size, minSpaceSize());
return UnsignedUtils.roundDown(size, getAlignment());
}

@Uninterruptible(reason = "Used in uninterruptible code.", mayBeInlined = true)
static boolean isAligned(UnsignedWord size) {
return UnsignedUtils.isAMultiple(size, minSpaceSize());
return UnsignedUtils.isAMultiple(size, getAlignment());
}

@Fold
static UnsignedWord minSpaceSize() {
return getAlignment().multiply(MIN_SPACE_SIZE_IN_ALIGNED_CHUNKS);
}

@Uninterruptible(reason = "Used in uninterruptible code.", mayBeInlined = true)
Expand Down Expand Up @@ -240,10 +248,11 @@ public UnsignedWord getMinimumHeapSize() {

protected SizeParameters computeSizeParameters() {
UnsignedWord addressSpaceSize = ReferenceAccess.singleton().getAddressSpaceSize();
UnsignedWord minAllSpaces = minSpaceSize().multiply(2); // eden, old
UnsignedWord minYoungSpaces = minSpaceSize(); // eden
if (HeapParameters.getMaxSurvivorSpaces() > 0) {
minAllSpaces = minAllSpaces.add(minSpaceSize().multiply(2)); // survivor from and to
minYoungSpaces = minYoungSpaces.add(minSpaceSize().multiply(2)); // survivor from and to
}
UnsignedWord minAllSpaces = minYoungSpaces.add(minSpaceSize()); // old

UnsignedWord maxHeap;
long optionMax = SubstrateGCOptions.MaxHeapSize.getValue();
Expand All @@ -267,6 +276,7 @@ protected SizeParameters computeSizeParameters() {
maxHeap = reasonableMax;
}
}
UnsignedWord unadjustedMaxHeap = maxHeap;
maxHeap = UnsignedUtils.clamp(alignDown(maxHeap), minAllSpaces, alignDown(addressSpaceSize));

UnsignedWord maxYoung;
Expand All @@ -278,16 +288,12 @@ protected SizeParameters computeSizeParameters() {
} else {
maxYoung = maxHeap.unsignedDivide(AbstractCollectionPolicy.NEW_RATIO + 1);
}
maxYoung = UnsignedUtils.clamp(alignUp(maxYoung), minSpaceSize(), maxHeap);
maxYoung = UnsignedUtils.clamp(alignDown(maxYoung), minYoungSpaces, maxHeap.subtract(minSpaceSize()));

UnsignedWord maxOld = maxHeap.subtract(maxYoung);
maxOld = minSpaceSize(alignUp(maxOld));
UnsignedWord maxOld = alignDown(maxHeap.subtract(maxYoung));
maxHeap = maxYoung.add(maxOld);
if (maxHeap.aboveThan(addressSpaceSize)) {
maxYoung = alignDown(maxYoung.subtract(minSpaceSize()));
maxHeap = maxYoung.add(maxOld);
VMError.guarantee(maxHeap.belowOrEqual(addressSpaceSize) && maxYoung.aboveOrEqual(minSpaceSize()));
}
VMError.guarantee(maxOld.aboveOrEqual(minSpaceSize()) && maxHeap.belowOrEqual(addressSpaceSize) &&
(maxHeap.belowOrEqual(unadjustedMaxHeap) || unadjustedMaxHeap.belowThan(minAllSpaces)));

UnsignedWord minHeap = WordFactory.zero();
long optionMin = SubstrateGCOptions.MinHeapSize.getValue();
Expand All @@ -296,19 +302,15 @@ protected SizeParameters computeSizeParameters() {
}
minHeap = UnsignedUtils.clamp(alignUp(minHeap), minAllSpaces, maxHeap);

UnsignedWord initialHeap;
if (PhysicalMemory.isInitialized()) {
initialHeap = UnsignedUtils.fromDouble(UnsignedUtils.toDouble(PhysicalMemory.getCachedSize()) / 100 * AbstractCollectionPolicy.INITIAL_HEAP_MEMORY_PERCENT);
} else {
initialHeap = AbstractCollectionPolicy.SMALL_HEAP_SIZE;
}
UnsignedWord initialHeap = AbstractCollectionPolicy.SMALL_HEAP_SIZE;
initialHeap = UnsignedUtils.clamp(alignUp(initialHeap), minHeap, maxHeap);

UnsignedWord initialYoung;
if (initialHeap.equal(maxHeap)) {
initialYoung = maxYoung;
} else {
initialYoung = UnsignedUtils.clamp(alignUp(initialHeap.unsignedDivide(AbstractCollectionPolicy.NEW_RATIO + 1)), minSpaceSize(), maxYoung);
initialYoung = initialHeap.unsignedDivide(AbstractCollectionPolicy.NEW_RATIO + 1);
initialYoung = UnsignedUtils.clamp(alignUp(initialYoung), minYoungSpaces, maxYoung);
}
UnsignedWord initialSurvivor = WordFactory.zero();
if (HeapParameters.getMaxSurvivorSpaces() > 0) {
Expand All @@ -320,9 +322,11 @@ protected SizeParameters computeSizeParameters() {
* generation, which we can exceed the (current) old gen size while copying during
* collections.
*/
initialSurvivor = minSpaceSize(alignUp(initialYoung.unsignedDivide(AbstractCollectionPolicy.INITIAL_SURVIVOR_RATIO)));
initialSurvivor = initialYoung.unsignedDivide(AbstractCollectionPolicy.INITIAL_SURVIVOR_RATIO);
initialSurvivor = minSpaceSize(alignDown(initialSurvivor));
}
UnsignedWord initialEden = minSpaceSize(alignUp(initialYoung.subtract(initialSurvivor.multiply(2))));
UnsignedWord initialEden = initialYoung.subtract(initialSurvivor.multiply(2));
initialEden = minSpaceSize(alignDown(initialEden));

return new SizeParameters(maxHeap, maxYoung, initialHeap, initialEden, initialSurvivor, minHeap);
}
Expand Down
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