spark UnsafeMemoryAllocator 源码
spark UnsafeMemoryAllocator 代码
文件路径：/common/unsafe/src/main/java/org/apache/spark/unsafe/memory/UnsafeMemoryAllocator.java
/*
* 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 simple {@link MemoryAllocator} that uses {@code Unsafe} to allocate off-heap memory.
*/
public class UnsafeMemoryAllocator implements MemoryAllocator {
@Override
public MemoryBlock allocate(long size) throws OutOfMemoryError {
long address = Platform.allocateMemory(size);
MemoryBlock memory = new MemoryBlock(null, address, size);
if (MemoryAllocator.MEMORY_DEBUG_FILL_ENABLED) {
memory.fill(MemoryAllocator.MEMORY_DEBUG_FILL_CLEAN_VALUE);
}
return memory;
}
@Override
public void free(MemoryBlock memory) {
assert (memory.obj == null) :
"baseObject not null; are you trying to use the off-heap allocator to free on-heap memory?";
assert (memory.pageNumber != MemoryBlock.FREED_IN_ALLOCATOR_PAGE_NUMBER) :
"page has already been freed";
assert ((memory.pageNumber == MemoryBlock.NO_PAGE_NUMBER)
|| (memory.pageNumber == MemoryBlock.FREED_IN_TMM_PAGE_NUMBER)) :
"TMM-allocated pages must be freed via TMM.freePage(), not directly in allocator free()";
if (MemoryAllocator.MEMORY_DEBUG_FILL_ENABLED) {
memory.fill(MemoryAllocator.MEMORY_DEBUG_FILL_FREED_VALUE);
}
Platform.freeMemory(memory.offset);
// As an additional layer of defense against use-after-free bugs, we mutate the
// MemoryBlock to reset its pointer.
memory.offset = 0;
// Mark the page as freed (so we can detect double-frees).
memory.pageNumber = MemoryBlock.FREED_IN_ALLOCATOR_PAGE_NUMBER;
}
}
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