org.apache.cassandra.io.util.DiskOptimizationStrategy Maven / Gradle / Ivy
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* 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,
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.cassandra.io.util;
public interface DiskOptimizationStrategy
{
int MIN_BUFFER_SIZE = 1 << 12; // 4096, the typical size of a page in the OS cache
int MIN_BUFFER_SIZE_MASK = MIN_BUFFER_SIZE - 1;
// The maximum buffer size, we will never buffer more than this size. Further,
// when the limiter is not null, i.e. when throttling is enabled, we read exactly
// this size, since when throttling the intention is to eventually read everything,
// see CASSANDRA-8630
// NOTE: this size is chosen both for historical consistency, as a reasonable upper bound,
// and because our BufferPool currently has a maximum allocation size of this.
int MAX_BUFFER_SIZE = 1 << 16; // 64k
/**
* @param recordSize record size
* @return the buffer size for a given record size.
*/
int bufferSize(long recordSize);
/**
* Round up to the next multiple of 4k but no more than {@link #MAX_BUFFER_SIZE}.
*/
default int roundBufferSize(long size)
{
if (size <= 0)
return MIN_BUFFER_SIZE;
size = (size + MIN_BUFFER_SIZE_MASK) & ~MIN_BUFFER_SIZE_MASK;
return (int)Math.min(size, MAX_BUFFER_SIZE);
}
/**
* Round either up or down to the next power of two, which is required by the
* {@link org.apache.cassandra.cache.ChunkCache.CachingRebufferer}, but capping between {@link #MIN_BUFFER_SIZE}
* and {@link #MAX_BUFFER_SIZE}.
*
* @param size - the size to round to a power of two, normally this is a buffer size that was previously
* returned by a {@link #bufferSize(long)}.
* @param roundUp - whether to round up or down
*
* @return a value rounded to a power of two but never bigger than {@link #MAX_BUFFER_SIZE} or smaller than {@link #MIN_BUFFER_SIZE}.
*/
static int roundForCaching(int size, boolean roundUp)
{
if (size <= MIN_BUFFER_SIZE)
return MIN_BUFFER_SIZE;
int ret = roundUp
? 1 << (32 - Integer.numberOfLeadingZeros(size - 1))
: Integer.highestOneBit(size);
return Math.min(MAX_BUFFER_SIZE, ret);
}
}