Github user kiszk commented on a diff in the pull request: https://github.com/apache/spark/pull/19222#discussion_r138786324 --- Diff: common/unsafe/src/main/java/org/apache/spark/unsafe/memory/ByteArrayMemoryBlock.java --- @@ -0,0 +1,74 @@ +/* + * 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.unsafe.memory; + +import org.apache.spark.unsafe.Platform; + +/** + * A consecutive block of memory, starting at a {@link MemoryLocation} with a fixed size. + */ +public class ByteArrayMemoryBlock extends MemoryLocation implements MemoryBlock { --- End diff -- @hvanhovell I agree with your concern about performance due to creating a class hierarchy. This implementation uses class hierarchy for two cases 1. Statically select target method using signature (e.g. Platform.getInt()) 2. Dynamically select target method using receiver (e.g. MemoryBlock.getBaseOffset()) Case 1 does not affect performance since it is resolved at javac. Case 2 is your concern. Since case 2. is used mainly for `getBaseObject()` and `getBaseOffset()` at performance critical path. They must be `final method`. 1. `MemoryLocation` is dropped 2. Several implementation classes extends `MemoryBlock` after making `MemoryBlock` abstract` as follows: ```java public abstract class MemoryBlock { Object obj; long offset; public MemoryBlock(Object obj, long offset) { this.obj = obj; this.offset = offset; } public final Object getBaseObject() { return obj; } public final long getBaseOffset() { return offset; } abstract long size(); abstract void setPageNumber(int pageNum); abstract int getPageNumber(); abstract void fill(byte value); abstract MemoryBlock allocate(long offset, long size); } ``` What do you think?
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