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/*
* 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 javax.annotation.concurrent.GuardedBy
/**
* Manages bookkeeping for an adjustable-sized region of memory. This class is internal to
* the [[MemoryManager]]. See subclasses for more details.
*
* @param lock a [[MemoryManager]] instance, used for synchronization. We purposely erase the type
* to `Object` to avoid programming errors, since this object should only be used for
* synchronization purposes.
*/
private[memory] abstract class MemoryPool(lock: Object) {
@GuardedBy("lock")
private[this] var _poolSize: Long = 0
/**
* Returns the current size of the pool, in bytes.
*/
final def poolSize: Long = lock.synchronized {
_poolSize
}
/**
* Returns the amount of free memory in the pool, in bytes.
*/
final def memoryFree: Long = lock.synchronized {
_poolSize - memoryUsed
}
/**
* Expands the pool by `delta` bytes.
*/
final def incrementPoolSize(delta: Long): Unit = lock.synchronized {
require(delta >= 0)
_poolSize += delta
}
/**
* Shrinks the pool by `delta` bytes.
*/
final def decrementPoolSize(delta: Long): Unit = lock.synchronized {
require(delta >= 0)
require(delta <= _poolSize)
require(_poolSize - delta >= memoryUsed)
_poolSize -= delta
}
/**
* Returns the amount of used memory in this pool (in bytes).
*/
def memoryUsed: Long
}
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