| /* |
| * 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 class SsdDiskOptimizationStrategy implements DiskOptimizationStrategy |
| { |
| private final double diskOptimizationPageCrossChance; |
| |
| public SsdDiskOptimizationStrategy(double diskOptimizationPageCrossChance) |
| { |
| this.diskOptimizationPageCrossChance = diskOptimizationPageCrossChance; |
| } |
| |
| /** |
| * For solid state disks only add one page if the chance of crossing to the next page is more |
| * than a predifined value. |
| * |
| * @see org.apache.cassandra.config.Config#disk_optimization_page_cross_chance |
| */ |
| @Override |
| public int bufferSize(long recordSize) |
| { |
| // The crossing probability is calculated assuming a uniform distribution of record |
| // start position in a page, so it's the record size modulo the page size divided by |
| // the total page size. |
| double pageCrossProbability = (recordSize % 4096) / 4096.; |
| // if the page cross probability is equal or bigger than disk_optimization_page_cross_chance we add one page |
| if ((pageCrossProbability - diskOptimizationPageCrossChance) > -1e-16) |
| recordSize += 4096; |
| |
| return roundBufferSize(recordSize); |
| } |
| } |