| /* |
| * 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. |
| */ |
| |
| namespace Apache.Ignite.Core.Configuration |
| { |
| /// <summary> |
| /// Memory page eviction mode. |
| /// Only data pages, that store key-value entries, are eligible for eviction. |
| /// The other types of pages, like index or system pages, are not evictable. |
| /// </summary> |
| public enum DataPageEvictionMode |
| { |
| /// <summary> |
| /// Eviction is disabled. |
| /// </summary> |
| Disabled, |
| |
| /// <summary> |
| /// Random-LRU algorithm. |
| /// <para /> |
| /// Once a memory region defined by a memory policy is configured, an off-heap array is allocated to track |
| /// last usage timestamp for every individual data page. The size of the array equals to |
| /// <see cref="DataRegionConfiguration.MaxSize"/> / <see cref="DataStorageConfiguration.PageSize"/>. |
| /// <para /> |
| /// When a data page is accessed, its timestamp gets updated in the tracking array. The page index in the |
| /// tracking array equals to pageAddress / <see cref="DataRegionConfiguration.MaxSize"/>. |
| /// <para /> |
| /// When some pages need to be evicted, the algorithm randomly chooses 5 indexes from the tracking array and |
| /// evicts a page with the latest timestamp. If some of the indexes point to non-data pages |
| /// (index or system pages) then the algorithm picks other pages. |
| /// </summary> |
| RandomLru, |
| |
| /// <summary> |
| /// Activates Random-2-LRU algorithm which is a scan resistant version of Random-LRU. |
| /// <para /> |
| /// This algorithm differs from Random-LRU only in a way that two latest access timestamps are stored for every |
| /// data page. At the eviction time, a minimum between two latest timestamps is taken for further |
| /// comparison with minimums of other pages that might be evicted. LRU-2 outperforms LRU by |
| /// resolving "one-hit wonder" problem - if a data page is accessed rarely, but accidentally accessed once, |
| /// its protected from eviction for a long time. |
| /// </summary> |
| Random2Lru |
| } |
| } |