Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/9241#discussion_r43457537
--- Diff: core/src/main/java/org/apache/spark/memory/MemoryConsumer.java ---
@@ -0,0 +1,131 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.memory;
+
+
+import java.io.IOException;
+
+import org.apache.spark.unsafe.memory.MemoryBlock;
+
+
+/**
+ * An memory consumer of TaskMemoryManager, which support spilling.
+ */
+public abstract class MemoryConsumer {
+
+ private final TaskMemoryManager taskMemoryManager;
+ private final long pageSize;
+ private long used;
+
+ protected MemoryConsumer(TaskMemoryManager taskMemoryManager, long
pageSize) {
+ this.taskMemoryManager = taskMemoryManager;
+ if (pageSize == 0) {
+ pageSize = taskMemoryManager.pageSizeBytes();
+ }
+ this.pageSize = pageSize;
+ this.used = 0;
+ }
+
+ protected MemoryConsumer(TaskMemoryManager taskMemoryManager) {
+ this(taskMemoryManager, taskMemoryManager.pageSizeBytes());
+ }
+
+ /**
+ * Returns the size of used memory in bytes.
+ */
+ long getUsed() {
+ return used;
+ }
+
+ /**
+ * Force spill during building.
+ *
+ * For testing.
+ */
+ public void spill() throws IOException {
+ spill(Long.MAX_VALUE, this);
+ }
+
+ /**
+ * Spill some data to disk to release memory, which will be called by
TaskMemoryManager
+ * when there is not enough memory for the task.
+ *
+ * This should be implemented by subclass.
+ *
+ * Note: In order to avoid possible deadlock, should not call
acquireMemory() from spill().
+ *
+ * @param size the amount of memory should be released
+ * @param trigger the MemoryConsumer that trigger this spilling
+ * @return the amount of released memory in bytes
+ * @throws IOException
+ */
+ public abstract long spill(long size, MemoryConsumer trigger) throws
IOException;
+
+ /**
+ * Acquire `size` bytes memory.
+ *
+ * If there is not enough memory, throws OutOfMemoryError.
+ */
+ protected void acquireMemory(long size) {
+ long got = taskMemoryManager.acquireExecutionMemory(size, this);
+ if (got < size) {
+ taskMemoryManager.releaseExecutionMemory(got, this);
+ taskMemoryManager.showMemoryUsage();
+ throw new OutOfMemoryError("Could not acquire " + size + " bytes of
memory, got " + got);
+ }
+ used += got;
+ }
+
+ /**
+ * Release `size` bytes memory.
+ */
+ protected void releaseMemory(long size) {
+ taskMemoryManager.releaseExecutionMemory(size, this);
+ used -= size;
+ }
+
+ /**
+ * Allocate a memory block with at least `required` bytes.
+ *
+ * Throws IOException if there is not enough memory.
+ *
+ * @throws OutOfMemoryError
+ */
+ protected MemoryBlock allocatePage(long required) {
+ MemoryBlock page = taskMemoryManager.allocatePage(Math.max(pageSize,
required), this);
+ if (page == null || page.size() < required) {
+ long got = 0;
+ if (page != null) {
+ got = page.size();
+ freePage(page);
+ }
+ taskMemoryManager.showMemoryUsage();
+ throw new OutOfMemoryError("Unable to acquire " + required + " bytes
of memory, got " + got);
+ }
+ used += page.size();
+ return page;
+ }
+
+ /**
+ * Free a memory block.
+ */
+ protected void freePage(MemoryBlock page) {
+ taskMemoryManager.freePage(page, this);
+ used -= page.size();
--- End diff --
Again, maybe an invalid concern, but is it safe to call `page.size()` on a
freed page?
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