| /* |
| * 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.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); |
| } |
| } |