/*
* 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);
}
}