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[GR-71288] Reduce default JFR global buffer size to lower footprint. #12510

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[GR-71288] Reduce default JFR global buffer size to lower footprint. #12510

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fe7d3da
adjust global buffer defaults
roberttoyonaga Nov 7, 2025
46fe33e
Set default size at build-time.
christianhaeubl Nov 10, 2025
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76 changes: 45 additions & 31 deletions substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrOptionSet.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,9 +28,9 @@
import org.graalvm.nativeimage.Platforms;

import com.oracle.svm.core.os.VirtualMemoryProvider;
import com.oracle.svm.core.util.BasedOnJDKFile;

import jdk.graal.compiler.core.common.NumUtil;
import jdk.jfr.internal.Options;

/**
* Holds all JFR-related options that can be set by the user. It is also used to validate and adjust
Expand All @@ -44,18 +44,32 @@
* level via {@link jdk.jfr.internal.JVM}. The option values are stored here until they are
* eventually used when first recording is created and JFR is initialized.
*/
@BasedOnJDKFile("https://github.com/openjdk/jdk/blob/jdk-25-ga/src/jdk.jfr/share/classes/jdk/jfr/internal/Options.java#L48-L55")
@BasedOnJDKFile("https://github.com/openjdk/jdk/blob/jdk-25-ga/src/jdk.jfr/share/classes/jdk/jfr/internal/Options.java#L65-L69")
public class JfrOptionSet {
private static final int MEMORY_SIZE = 1;
private static final int GLOBAL_BUFFER_SIZE = 2;
private static final int GLOBAL_BUFFER_COUNT = 4;
private static final int THREAD_BUFFER_SIZE = 8;
private static final int MEMORY_SIZE_BIT = 1;
private static final int GLOBAL_BUFFER_SIZE_BIT = 2;
private static final int GLOBAL_BUFFER_COUNT_BIT = 4;
private static final int THREAD_BUFFER_SIZE_BIT = 8;

/*
* Use 2.5 MB by default (instead of 10 MB on HotSpot). We explicitly hard-code the default
* values here to avoid that those values are copied from HotSpot at build-time because
* completely different values might be set there if JFR is enabled at build-time as well.
*/
private static final long DEFAULT_GLOBAL_BUFFER_COUNT = 10;
private static final long DEFAULT_GLOBAL_BUFFER_SIZE = 256 * 1024;
private static final long DEFAULT_MEMORY_SIZE = DEFAULT_GLOBAL_BUFFER_COUNT * DEFAULT_GLOBAL_BUFFER_SIZE;
private static final long DEFAULT_THREAD_BUFFER_SIZE = 8 * 1024;
private static final int DEFAULT_STACK_DEPTH = 64;
private static final long DEFAULT_MAX_CHUNK_SIZE = 12 * 1024 * 1024;

private static final long MAX_ADJUSTED_GLOBAL_BUFFER_SIZE = 1 * 1024 * 1024;
private static final long MIN_ADJUSTED_GLOBAL_BUFFER_SIZE_CUTOFF = 512 * 1024;
private static final long MIN_GLOBAL_BUFFER_SIZE = 64 * 1024;
private static final long MIN_GLOBAL_BUFFER_COUNT = 2;
private static final long MIN_THREAD_BUFFER_SIZE = 4 * 1024;
private static final long MIN_MEMORY_SIZE = 1 * 1024 * 1024;
private static final long MIN_MEMORY_SIZE = 1024 * 1024;

public final JfrOptionLong threadBufferSize;
public final JfrOptionLong globalBufferSize;
Expand All @@ -66,12 +80,12 @@ public class JfrOptionSet {

@Platforms(Platform.HOSTED_ONLY.class)
public JfrOptionSet() {
threadBufferSize = new JfrOptionLong(Options.getThreadBufferSize());
globalBufferSize = new JfrOptionLong(Options.getGlobalBufferSize());
globalBufferCount = new JfrOptionLong(Options.getGlobalBufferCount());
memorySize = new JfrOptionLong(Options.getMemorySize());
maxChunkSize = new JfrOptionLong(Options.getMaxChunkSize());
stackDepth = new JfrOptionLong(Options.getStackDepth());
threadBufferSize = new JfrOptionLong(DEFAULT_THREAD_BUFFER_SIZE);
globalBufferSize = new JfrOptionLong(DEFAULT_GLOBAL_BUFFER_SIZE);
globalBufferCount = new JfrOptionLong(DEFAULT_GLOBAL_BUFFER_COUNT);
memorySize = new JfrOptionLong(DEFAULT_MEMORY_SIZE);
maxChunkSize = new JfrOptionLong(DEFAULT_MAX_CHUNK_SIZE);
stackDepth = new JfrOptionLong(DEFAULT_STACK_DEPTH);
}

public void validateAndAdjustMemoryOptions() {
Expand Down Expand Up @@ -120,55 +134,55 @@ private void adjustMemoryOptions() {

int setOfOptions = 0;
if (memorySize.isUserValue()) {
setOfOptions |= MEMORY_SIZE;
setOfOptions |= MEMORY_SIZE_BIT;
}
if (globalBufferSize.isUserValue()) {
setOfOptions |= GLOBAL_BUFFER_SIZE;
setOfOptions |= GLOBAL_BUFFER_SIZE_BIT;
}
if (globalBufferCount.isUserValue()) {
setOfOptions |= GLOBAL_BUFFER_COUNT;
setOfOptions |= GLOBAL_BUFFER_COUNT_BIT;
}
if (threadBufferSize.isUserValue()) {
setOfOptions |= THREAD_BUFFER_SIZE;
setOfOptions |= THREAD_BUFFER_SIZE_BIT;
}

switch (setOfOptions) {
case MEMORY_SIZE | THREAD_BUFFER_SIZE:
case MEMORY_SIZE:
case MEMORY_SIZE_BIT | THREAD_BUFFER_SIZE_BIT:
case MEMORY_SIZE_BIT:
memoryAndThreadBufferSize();
break;
case MEMORY_SIZE | GLOBAL_BUFFER_COUNT:
case MEMORY_SIZE_BIT | GLOBAL_BUFFER_COUNT_BIT:
memorySizeAndBufferCount();
break;
case MEMORY_SIZE | GLOBAL_BUFFER_SIZE | THREAD_BUFFER_SIZE:
case MEMORY_SIZE_BIT | GLOBAL_BUFFER_SIZE_BIT | THREAD_BUFFER_SIZE_BIT:
assert threadBufferSize.isUserValue();
// fall through
case MEMORY_SIZE | GLOBAL_BUFFER_SIZE:
case MEMORY_SIZE_BIT | GLOBAL_BUFFER_SIZE_BIT:
memorySizeAndGlobalBufferSize();
break;
case MEMORY_SIZE | GLOBAL_BUFFER_SIZE | GLOBAL_BUFFER_COUNT:
case MEMORY_SIZE | GLOBAL_BUFFER_SIZE | GLOBAL_BUFFER_COUNT | THREAD_BUFFER_SIZE:
case MEMORY_SIZE_BIT | GLOBAL_BUFFER_SIZE_BIT | GLOBAL_BUFFER_COUNT_BIT:
case MEMORY_SIZE_BIT | GLOBAL_BUFFER_SIZE_BIT | GLOBAL_BUFFER_COUNT_BIT | THREAD_BUFFER_SIZE_BIT:
allOptionsSet();
break;
case GLOBAL_BUFFER_SIZE | GLOBAL_BUFFER_COUNT | THREAD_BUFFER_SIZE:
case GLOBAL_BUFFER_SIZE_BIT | GLOBAL_BUFFER_COUNT_BIT | THREAD_BUFFER_SIZE_BIT:
assert globalBufferCount.isUserValue();
assert threadBufferSize.isUserValue();
// fall through
case GLOBAL_BUFFER_SIZE | GLOBAL_BUFFER_COUNT:
case GLOBAL_BUFFER_SIZE_BIT | GLOBAL_BUFFER_COUNT_BIT:
assert globalBufferSize.isUserValue();
// fall through
case GLOBAL_BUFFER_SIZE | THREAD_BUFFER_SIZE:
case GLOBAL_BUFFER_COUNT:
case GLOBAL_BUFFER_SIZE:
case GLOBAL_BUFFER_SIZE_BIT | THREAD_BUFFER_SIZE_BIT:
case GLOBAL_BUFFER_COUNT_BIT:
case GLOBAL_BUFFER_SIZE_BIT:
globalBufferSize();
break;
case MEMORY_SIZE | GLOBAL_BUFFER_COUNT | THREAD_BUFFER_SIZE:
case MEMORY_SIZE_BIT | GLOBAL_BUFFER_COUNT_BIT | THREAD_BUFFER_SIZE_BIT:
assert memorySize.isUserValue();
// fall through
case GLOBAL_BUFFER_COUNT | THREAD_BUFFER_SIZE:
case GLOBAL_BUFFER_COUNT_BIT | THREAD_BUFFER_SIZE_BIT:
assert globalBufferCount.isUserValue();
// fall through
case THREAD_BUFFER_SIZE:
case THREAD_BUFFER_SIZE_BIT:
threadBufferSize();
break;
default:
Expand Down