diff --git a/indexing-service/src/main/java/org/apache/druid/indexing/overlord/ForkingTaskRunner.java b/indexing-service/src/main/java/org/apache/druid/indexing/overlord/ForkingTaskRunner.java
index ab7de6cf3c8..f07a859e777 100644
--- a/indexing-service/src/main/java/org/apache/druid/indexing/overlord/ForkingTaskRunner.java
+++ b/indexing-service/src/main/java/org/apache/druid/indexing/overlord/ForkingTaskRunner.java
@@ -37,6 +37,7 @@ import com.google.common.io.ByteSource;
 import com.google.common.io.ByteStreams;
 import com.google.common.io.FileWriteMode;
 import com.google.common.io.Files;
+import com.google.common.math.IntMath;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.common.util.concurrent.MoreExecutors;
@@ -58,6 +59,7 @@ import org.apache.druid.java.util.common.ISE;
 import org.apache.druid.java.util.common.StringUtils;
 import org.apache.druid.java.util.common.concurrent.Execs;
 import org.apache.druid.java.util.common.io.Closer;
+import org.apache.druid.java.util.common.lifecycle.LifecycleStart;
 import org.apache.druid.java.util.common.lifecycle.LifecycleStop;
 import org.apache.druid.java.util.emitter.EmittingLogger;
 import org.apache.druid.query.DruidMetrics;
@@ -67,6 +69,7 @@ import org.apache.druid.server.metrics.MonitorsConfig;
 import org.apache.druid.server.metrics.WorkerTaskCountStatsProvider;
 import org.apache.druid.tasklogs.TaskLogPusher;
 import org.apache.druid.tasklogs.TaskLogStreamer;
+import org.apache.druid.utils.JvmUtils;
 import org.joda.time.DateTime;
 import org.joda.time.Interval;
 
@@ -75,6 +78,7 @@ import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.math.RoundingMode;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Iterator;
@@ -105,6 +109,7 @@ public class ForkingTaskRunner
   private final StartupLoggingConfig startupLoggingConfig;
   private final WorkerConfig workerConfig;
 
+  private volatile int numProcessorsPerTask = -1;
   private volatile boolean stopping = false;
 
   private static final AtomicLong LAST_REPORTED_FAILED_TASK_COUNT = new AtomicLong();
@@ -214,6 +219,13 @@ public class ForkingTaskRunner
                         command.add("-cp");
                         command.add(taskClasspath);
 
+                        if (numProcessorsPerTask < 1) {
+                          // numProcessorsPerTask is set by start()
+                          throw new ISE("Not started");
+                        }
+
+                        command.add(StringUtils.format("-XX:ActiveProcessorCount=%d", numProcessorsPerTask));
+
                         Iterables.addAll(command, new QuotableWhiteSpaceSplitter(config.getJavaOpts()));
                         Iterables.addAll(command, config.getJavaOptsArray());
 
@@ -633,9 +645,10 @@ public class ForkingTaskRunner
   }
 
   @Override
+  @LifecycleStart
   public void start()
   {
-    // No state setup required
+    setNumProcessorsPerTask();
   }
 
   @Override
@@ -788,6 +801,20 @@ public class ForkingTaskRunner
     return successfulTaskCount - lastReportedSuccessfulTaskCount;
   }
 
+  @VisibleForTesting
+  void setNumProcessorsPerTask()
+  {
+    // Divide number of available processors by the number of tasks.
+    // This prevents various automatically-sized thread pools from being unreasonably large (we don't want each
+    // task to size its pools as if it is the only thing on the entire machine).
+
+    final int availableProcessors = JvmUtils.getRuntimeInfo().getAvailableProcessors();
+    numProcessorsPerTask = Math.max(
+        1,
+        IntMath.divide(availableProcessors, workerConfig.getCapacity(), RoundingMode.CEILING)
+    );
+  }
+
   protected static class ForkingTaskRunnerWorkItem extends TaskRunnerWorkItem
   {
     private final Task task;
diff --git a/indexing-service/src/test/java/org/apache/druid/indexing/overlord/ForkingTaskRunnerTest.java b/indexing-service/src/test/java/org/apache/druid/indexing/overlord/ForkingTaskRunnerTest.java
index 9e45d92ce5b..2d1a791586a 100644
--- a/indexing-service/src/test/java/org/apache/druid/indexing/overlord/ForkingTaskRunnerTest.java
+++ b/indexing-service/src/test/java/org/apache/druid/indexing/overlord/ForkingTaskRunnerTest.java
@@ -242,6 +242,7 @@ public class ForkingTaskRunnerTest
       }
     };
 
+    forkingTaskRunner.setNumProcessorsPerTask();
     final TaskStatus status = forkingTaskRunner.run(NoopTask.create()).get();
     Assert.assertEquals(TaskState.FAILED, status.getStatusCode());
     Assert.assertEquals(
@@ -312,6 +313,7 @@ public class ForkingTaskRunnerTest
       }
     };
 
+    forkingTaskRunner.setNumProcessorsPerTask();
     final TaskStatus status = forkingTaskRunner.run(task).get();
     Assert.assertEquals(TaskState.SUCCESS, status.getStatusCode());
     Assert.assertNull(status.getErrorMsg());
@@ -373,6 +375,7 @@ public class ForkingTaskRunnerTest
       }
     };
 
+    forkingTaskRunner.setNumProcessorsPerTask();
     final TaskStatus status = forkingTaskRunner.run(task).get();
     Assert.assertEquals(TaskState.FAILED, status.getStatusCode());
     Assert.assertEquals("task failure test", status.getErrorMsg());
@@ -441,6 +444,7 @@ public class ForkingTaskRunnerTest
       }
     };
 
+    forkingTaskRunner.setNumProcessorsPerTask();
     forkingTaskRunner.run(task).get();
     Assert.assertTrue(xmxJavaOptsArrayIndex.get() > xmxJavaOptsIndex.get());
     Assert.assertTrue(xmxJavaOptsIndex.get() >= 0);
@@ -509,6 +513,7 @@ public class ForkingTaskRunnerTest
       }
     };
 
+    forkingTaskRunner.setNumProcessorsPerTask();
     ExecutionException e = Assert.assertThrows(ExecutionException.class, () -> forkingTaskRunner.run(task).get());
     Assert.assertTrue(e.getMessage().endsWith(ForkingTaskRunnerConfig.JAVA_OPTS_ARRAY_PROPERTY
                                               + " in context of task: " + task.getId() + " must be an array of strings.")
diff --git a/services/src/main/java/org/apache/druid/cli/CliMiddleManager.java b/services/src/main/java/org/apache/druid/cli/CliMiddleManager.java
index ed424ba037f..f423982b9f7 100644
--- a/services/src/main/java/org/apache/druid/cli/CliMiddleManager.java
+++ b/services/src/main/java/org/apache/druid/cli/CliMiddleManager.java
@@ -137,7 +137,7 @@ public class CliMiddleManager extends ServerRunnable
             JsonConfigProvider.bind(binder, "druid.worker", WorkerConfig.class);
 
             binder.bind(TaskRunner.class).to(ForkingTaskRunner.class);
-            binder.bind(ForkingTaskRunner.class).in(LazySingleton.class);
+            binder.bind(ForkingTaskRunner.class).in(ManageLifecycle.class);
             binder.bind(WorkerTaskCountStatsProvider.class).to(ForkingTaskRunner.class);
 
             binder.bind(IndexingServiceClient.class).to(HttpIndexingServiceClient.class).in(LazySingleton.class);