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[GR-59326] Ensure ForkJoin commonPool parallelism always respects NativeImageOptions.NumberOfThreads. #9950

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Oct 24, 2024
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[GR-59326] Ensure ForkJoin commonPool parallelism always respects NativeImageOptions.NumberOfThreads. #9950

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1 change: 1 addition & 0 deletions substratevm/CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@ At runtime, premain runtime options are set along with main class' arguments in
* (GR-58000) Support for `GetStringUTFLengthAsLong` added in JNI_VERSION_24 ([JDK-8328877](https://bugs.openjdk.org/browse/JDK-8328877))
* (GR-58383) The length of the printed stack trace when using `-XX:MissingRegistrationReportingMode=Warn` can now be set with `-XX:MissingRegistrationWarnContextLines=` and its default length is now 8.
* (GR-58914) `ActiveProcessorCount` must be set at isolate or VM creation time.
* (GR-59326) Ensure builder ForkJoin commonPool parallelism always respects NativeImageOptions.NumberOfThreads.

## GraalVM for JDK 23 (Internal Version 24.1.0)
* (GR-51520) The old class initialization strategy, which was deprecated in GraalVM for JDK 22, is removed. The option `StrictImageHeap` no longer has any effect.
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44 changes: 21 additions & 23 deletions substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageOptions.java
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Expand Up @@ -38,9 +38,9 @@
import com.oracle.graal.pointsto.reports.ReportUtils;
import com.oracle.svm.core.SubstrateOptions;
import com.oracle.svm.core.option.APIOption;
import com.oracle.svm.core.option.AccumulatingLocatableMultiOptionValue;
import com.oracle.svm.core.option.BundleMember;
import com.oracle.svm.core.option.HostedOptionKey;
import com.oracle.svm.core.option.AccumulatingLocatableMultiOptionValue;
import com.oracle.svm.core.option.SubstrateOptionsParser;
import com.oracle.svm.core.util.InterruptImageBuilding;
import com.oracle.svm.core.util.UserError;
Expand Down Expand Up @@ -214,28 +214,26 @@ public static int getActualNumberOfThreads() {
}

public static void setCommonPoolParallelism(OptionValues optionValues) {
if (NativeImageOptions.NumberOfThreads.hasBeenSet(optionValues)) {
/*
* The main thread always helps to process tasks submitted to the common pool (e.g., see
* ForkJoinPool#awaitTermination()), so subtract one from the number of threads. The
* common pool can be disabled "by setting the parallelism property to zero" (see
* ForkJoinPool's javadoc).
*/
int numberOfCommonPoolThreads = NativeImageOptions.NumberOfThreads.getValue(optionValues) - 1;
String commonPoolParallelismProperty = "java.util.concurrent.ForkJoinPool.common.parallelism";
assert System.getProperty(commonPoolParallelismProperty) == null : commonPoolParallelismProperty + " already set";
System.setProperty(commonPoolParallelismProperty, "" + numberOfCommonPoolThreads);
int actualCommonPoolParallelism = ForkJoinPool.commonPool().getParallelism();
/*
* getParallelism() returns at least 1, even in single-threaded mode where common pool
* is disabled.
*/
boolean isSingleThreadedMode = numberOfCommonPoolThreads == 0 && actualCommonPoolParallelism == 1;
if (!isSingleThreadedMode && actualCommonPoolParallelism != numberOfCommonPoolThreads) {
String warning = "Failed to set parallelism of common pool (actual parallelism is %s).".formatted(actualCommonPoolParallelism);
assert false : warning;
LogUtils.warning(warning);
}
/*
* The main thread always helps to process tasks submitted to the common pool (e.g., see
* ForkJoinPool#awaitTermination()), so subtract one from the number of threads. The common
* pool can be disabled "by setting the parallelism property to zero" (see ForkJoinPool's
* javadoc).
*/
int numberOfCommonPoolThreads = NativeImageOptions.NumberOfThreads.getValueOrDefault(optionValues.getMap()) - 1;
String commonPoolParallelismProperty = "java.util.concurrent.ForkJoinPool.common.parallelism";
assert System.getProperty(commonPoolParallelismProperty) == null : commonPoolParallelismProperty + " already set";
System.setProperty(commonPoolParallelismProperty, "" + numberOfCommonPoolThreads);
int actualCommonPoolParallelism = ForkJoinPool.commonPool().getParallelism();
/*
* getParallelism() returns at least 1, even in single-threaded mode where common pool is
* disabled.
*/
boolean isSingleThreadedMode = numberOfCommonPoolThreads == 0 && actualCommonPoolParallelism == 1;
if (!isSingleThreadedMode && actualCommonPoolParallelism != numberOfCommonPoolThreads) {
String warning = "Failed to set parallelism of common pool (actual parallelism is %s).".formatted(actualCommonPoolParallelism);
assert false : warning;
LogUtils.warning(warning);
}
}

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