[GitHub] [flink] tillrohrmann commented on a change in pull request #14966: [FLINK-21417][core] Separate type-specific memory segments.

[GitBox <gi...@apache.org>]

tillrohrmann commented on a change in pull request #14966:
URL: https://github.com/apache/flink/pull/14966#discussion_r579644550



##########
File path: flink-core/src/main/java/org/apache/flink/core/memory/MemorySegmentFactory.java
##########
@@ -31,7 +31,7 @@
 import static org.apache.flink.util.Preconditions.checkArgument;
 
 /**
- * A factory for (hybrid) memory segments ({@link HybridMemorySegment}).
+ * A factory for (hybrid) memory segments ({@link OffHeapMemorySegment}).

Review comment:
       `A factory for {@link OffHeapMemorySegment}`.

##########
File path: flink-core/src/main/java/org/apache/flink/core/memory/OffHeapMemorySegment.java
##########
@@ -24,33 +24,22 @@
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
-import java.io.DataInput;
-import java.io.DataOutput;
-import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.function.Consumer;
 import java.util.function.Function;
 
 import static org.apache.flink.core.memory.MemoryUtils.getByteBufferAddress;
 
 /**
- * This class represents a piece of memory managed by Flink.
+ * This class represents a piece of off-heap memory managed by Flink.
  *
- * <p>The memory can be on-heap, off-heap direct or off-heap unsafe, this is transparently handled
- * by this class.
- *
- * <p>This class specializes byte access and byte copy calls for heap memory, while reusing the
- * multi-byte type accesses and cross-segment operations from the MemorySegment.
- *
- * <p>This class subsumes the functionality of the {@link
- * org.apache.flink.core.memory.HeapMemorySegment}, but is a bit less efficient for operations on
- * individual bytes.
+ * <p>The memory can direct or unsafe, this is transparently handled by this class.

Review comment:
       `can be`

##########
File path: flink-core/src/test/java/org/apache/flink/core/memory/HybridOffHeapDirectMemorySegmentTest.java
##########
@@ -51,7 +51,7 @@ MemorySegment createSegment(int size, Object owner) {
     @Test
     public void testHybridHeapSegmentSpecifics() {
         final int bufSize = 411;
-        HybridMemorySegment seg = (HybridMemorySegment) createSegment(bufSize);
+        OffHeapMemorySegment seg = (OffHeapMemorySegment) createSegment(bufSize);

Review comment:
       The cast should not be necessary if we change the return type of `createSegment`.

##########
File path: flink-core/src/test/java/org/apache/flink/core/memory/EndiannessAccessChecks.java
##########
@@ -37,19 +37,18 @@ public void testHeapSegment() {
 
     @Test
     public void testHybridOnHeapSegment() {
-        testBigAndLittleEndianAccessUnaligned(MemorySegmentFactory.wrap(new byte[11111]));
+        testBigAndLittleEndianAccessUnaligned(
+                MemorySegmentFactory.wrapHeapSegment(new byte[11111]));
     }
 
     @Test
     public void testHybridOffHeapSegment() {
-        testBigAndLittleEndianAccessUnaligned(
-                MemorySegmentFactory.allocateUnpooledOffHeapMemory(11111));
+        testBigAndLittleEndianAccessUnaligned(MemorySegmentFactory.allocateDirectSegment(11111));
     }
 
     @Test
     public void testHybridOffHeapUnsafeSegment() {

Review comment:
       Could be renamed into `testUnsafeOffHeapSegment`

##########
File path: flink-core/src/main/java/org/apache/flink/core/memory/MemorySegmentFactory.java
##########
@@ -130,7 +130,7 @@ public static MemorySegment allocateUnpooledOffHeapMemory(int size) {
      */
     public static MemorySegment allocateUnpooledOffHeapMemory(int size, Object owner) {

Review comment:
       Should we rename the factory methods to reflect which type of off heap memory they allocate?

##########
File path: flink-core/src/main/java/org/apache/flink/core/memory/UnsafeMemorySegment.java
##########
@@ -0,0 +1,69 @@
+/*
+ * 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.flink.core.memory;
+
+import org.apache.flink.annotation.Internal;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+import java.nio.ByteBuffer;
+
+/**
+ * This class represents a piece of unsafe off-heap memory managed by Flink.
+ *
+ * <p>Note that memory segments should usually not be allocated manually, but rather through the
+ * {@link MemorySegmentFactory}.
+ */
+@Internal
+public class UnsafeMemorySegment extends OffHeapMemorySegment {
+    @Nullable private final Runnable cleaner;
+
+    /**
+     * Creates a new memory segment that represents the memory backing the given unsafe byte buffer.
+     * Note that the given ByteBuffer must be direct {@link
+     * java.nio.ByteBuffer#allocateDirect(int)}, otherwise this method with throw an
+     * IllegalArgumentException.
+     *
+     * <p>The memory segment references the given owner.
+     *
+     * @param buffer The byte buffer whose memory is represented by this memory segment.
+     * @param owner The owner references by this memory segment.
+     * @param cleaner The cleaner to be called on free segment.
+     * @throws IllegalArgumentException Thrown, if the given ByteBuffer is not direct.
+     */
+    UnsafeMemorySegment(
+            @Nonnull ByteBuffer buffer, @Nullable Object owner, @Nullable Runnable cleaner) {

Review comment:
       When is `cleaner` `null`?

##########
File path: flink-core/src/test/java/org/apache/flink/core/memory/HybridOffHeapUnsafeMemorySegmentTest.java
##########
@@ -26,7 +26,7 @@
 
 import static org.junit.Assert.assertTrue;
 
-/** Tests for the {@link HybridMemorySegment} in off-heap mode using unsafe memory. */
+/** Tests for the {@link OffHeapMemorySegment} in off-heap mode using unsafe memory. */
 @RunWith(Parameterized.class)
 public class HybridOffHeapUnsafeMemorySegmentTest extends MemorySegmentTestBase {

Review comment:
       Will be renamed later, right?

##########
File path: flink-core/src/test/java/org/apache/flink/core/memory/HybridOffHeapDirectMemorySegmentTest.java
##########
@@ -51,7 +51,7 @@ MemorySegment createSegment(int size, Object owner) {
     @Test
     public void testHybridHeapSegmentSpecifics() {

Review comment:
       Name of the test can be updated.

##########
File path: flink-core/src/test/java/org/apache/flink/core/memory/HybridOffHeapDirectMemorySegmentTest.java
##########
@@ -30,7 +30,7 @@
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
-/** Tests for the {@link HybridMemorySegment} in off-heap mode using direct memory. */
+/** Tests for the {@link OffHeapMemorySegment} in off-heap mode using direct memory. */
 @RunWith(Parameterized.class)
 public class HybridOffHeapDirectMemorySegmentTest extends MemorySegmentTestBase {

Review comment:
       I guess this test will be renamed in a later commit, right?

##########
File path: flink-core/src/test/java/org/apache/flink/core/memory/EndiannessAccessChecks.java
##########
@@ -37,19 +37,18 @@ public void testHeapSegment() {
 
     @Test
     public void testHybridOnHeapSegment() {
-        testBigAndLittleEndianAccessUnaligned(MemorySegmentFactory.wrap(new byte[11111]));
+        testBigAndLittleEndianAccessUnaligned(
+                MemorySegmentFactory.wrapHeapSegment(new byte[11111]));
     }
 
     @Test
     public void testHybridOffHeapSegment() {

Review comment:
       could be renamed into `testDirectOffHeapSegment`




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