C#并发容器之ConcurrentDictionary与普通Dictionary带锁性能详解

时间:2021-05-20

结果已经写在注释中

static void Main(string[] args){ var concurrentDictionary = new ConcurrentDictionary<int, string>(); var dictionary = new Dictionary<int, string>(); var sw = new Stopwatch(); sw.Start(); for (int i = 0; i < 1000000; i++) { lock (dictionary) { dictionary[i] = Item; } } sw.Stop(); Console.WriteLine("wrinting to dictionary with a lock: {0}", sw.Elapsed); //wrinting to dictionary with a lock: 00:00:00.0633939 sw.Restart(); for (int i = 0; i < 1000000; i++) { concurrentDictionary[i] = Item; } sw.Stop(); Console.WriteLine("wrinting to a concurrent dictionary: {0}", sw.Elapsed); //wrinting to a concurrent dictionary: 00:00:00.2889851 //对于写入操作并发词典要比普通带锁词典要慢 sw.Restart(); for (int i = 0; i < 1000000; i++) { lock (dictionary) { CurrentItem = dictionary[i]; } } sw.Stop(); Console.WriteLine("reading from dictionary with a lock: {0}", sw.Elapsed); //reading from dictionary with a lock: 00:00:00.0286066 sw.Restart(); for (int i = 0; i < 1000000; i++) { CurrentItem = concurrentDictionary[i]; } sw.Stop(); Console.WriteLine("reading from a concurrent dictionary: {0}", sw.Elapsed); //reading from a concurrent dictionary: 00:00:00.0196372 //对于读取操作并发词典要比普通带锁词典要快 //concurrentDictionary采用细粒度锁定[fine-grained locking] //普通带锁dictionary采用粗粒度锁定[coarse-grained locking] //在多核多线程的情况下concurrentDictionary将有更好的性能表现 sw.Restart(); Console.ReadKey();} const string Item = "Dictionary item";public static string CurrentItem;

补充:C#中普通字典(Dictionary)、并发字典(ConcurrentDictionary)、和哈希表(Hashtable)读写性能比较

一、说明

程序有时候需要并发多线程操作,多线程读取同一个容器内的东西是可以的,但是如果需要修改及写入到同一容器内,会有索引失败的问题,即两个进程同时向同一个位置写入内容,这种情况下需要通过lock(var),将容器锁定,也可以直接使用可并发读写的容器(ConcurrentDictionary)

测试分2部分,一次是写入操作,包含带锁写入和不带锁写入,其中每个里面又细分为写入字符串和写入一个类,还有一次是遍历操作,同样包含带锁读和不带锁读,其中也分为读取字符串和读取类。

二、测试结果

2.1、写入用时

2.2、遍历用时

2.3、结论

对于写入操作速度:普通词典 > HashTable > 并发词典

对于读操作速度:并发字典 > 带锁字典 > HashTable

无论普通字典还是HashTable,带锁花费的时间都要比不带锁慢,为了线程安全,肯定要牺牲时间的。

所以如果需要自己写入的话,推荐带锁普通字典,读写速度都很均衡。

三、测试代码如下

using System;using System.Collections;using System.Collections.Concurrent;using System.Collections.Generic;using System.ComponentModel;using System.Diagnostics;using System.Linq;using System.Text;using System.Threading;using System.Threading.Tasks; namespace BaseMultiThread{ class Program { static void Main(string[] args) { ConcurrentDictionary<int, string> _CctDic= new ConcurrentDictionary<int, string>(); ConcurrentDictionary<int, Student> _CctDicClass = new ConcurrentDictionary<int, Student>(); Dictionary<int, string> _Dic = new Dictionary<int, string>(); Dictionary<int, Student> _DicClass = new Dictionary<int, Student>(); Hashtable _Ht = new Hashtable(); Hashtable _HtClass = new Hashtable(); string _CurrentItem = ""; const string _Item = "字符串"; const int _NUM = 10000000;//执行次数 Student _CurrentStudent = null; Student student = new Student { Name = _Item, Age = 23 }; Stopwatch _SW = new Stopwatch(); //字符串写入字典(无锁) _SW.Start(); for (int i = 0; i < _NUM; i++) { _Dic[i] = _Item; } _SW.Stop(); Console.WriteLine("向字典写入【字符串】不添加锁(Lock)花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //字符串写入字典(有锁) _Dic = new Dictionary<int, string>(); _SW.Restart(); for (int i = 0; i < _NUM; i++) { lock (_Dic) { _Dic[i] = _Item; } } _SW.Stop(); Console.WriteLine("向字典写入【字符串】添加锁(Lock)花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //类写入字典(无锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { _DicClass[i] = student; } _SW.Stop(); Console.WriteLine("向子典写入【学生类】不添加锁(Lock)花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //类写入字典(有锁) _DicClass = new Dictionary<int, Student>(); _SW.Restart(); for (int i = 0; i < _NUM; i++) { lock (_DicClass) { _DicClass[i] = student; } } _SW.Stop(); Console.WriteLine("向子典写入【学生类】添加锁(Lock)花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); Console.WriteLine("----------------------------------------------------"); //字符串写入HashTable(无锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { _Ht[i] = _Item; } _SW.Stop(); Console.WriteLine("向HashTable写入【字符串】不添加锁(Lock)花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //字符串写入HashTable(有锁) _Ht = new Hashtable(); _SW.Restart(); for (int i = 0; i < _NUM; i++) { lock (_Ht) { _Ht[i] = _Item; } } _SW.Stop(); Console.WriteLine("向HashTable写入【字符串】添加锁(Lock)花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //类写入HashTable(无锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { _HtClass[i] = student; } _SW.Stop(); Console.WriteLine("向HashTable写入【学生类】不添加锁(Lock)花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //类写入HashTable(有锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { lock (_HtClass) { _HtClass[i] = student; } } _SW.Stop(); Console.WriteLine("向HashTable写入【学生类】添加锁(Lock)花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); Console.WriteLine("----------------------------------------------------------"); //字符串写入ConcurrentDictionary _SW.Restart(); for (int i = 0; i < _NUM; i++) { _CctDic[i] = _Item; } _SW.Stop(); Console.WriteLine("向ConcurrentDictionary写入【字符串】 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //类写入ConcurrentDictionary _SW.Restart(); for (int i = 0; i < _NUM; i++) { _CctDicClass[i] = student; } _SW.Stop(); Console.WriteLine("向ConcurrentDictionary写入【学生类】 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); Console.WriteLine("--------------------------------------------------------"); //遍历普通字典(无锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { _CurrentItem = _Dic[i]; } _SW.Stop(); Console.WriteLine("遍历【普通】字典(无锁) 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //遍历普通字典(有锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { lock (_Dic) { _CurrentItem = _Dic[i]; } } _SW.Stop(); Console.WriteLine("遍历【普通】字典(有锁) 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //遍历类字典(无锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { _CurrentStudent = _DicClass[i]; } _SW.Stop(); Console.WriteLine("遍历【学生类】字典(无锁) 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //遍历类字典(有锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { lock (_Dic) { _CurrentStudent = _DicClass[i]; } } _SW.Stop(); Console.WriteLine("遍历【学生类】字典(有锁) 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); Console.WriteLine("--------------------------------------------------------"); //遍历HashTable(无锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { _CurrentItem = _Ht[i].ToString(); } _SW.Stop(); Console.WriteLine("遍历【HashTable】字典(无锁) 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //遍历HashTable(有锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { lock (_Dic) { _CurrentItem = _Ht[i].ToString(); } } _SW.Stop(); Console.WriteLine("遍历【HashTable】字典(有锁) 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //遍历HashTable类(无锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { _CurrentStudent = (Student)_HtClass[i]; } _SW.Stop(); Console.WriteLine("遍历【HashTable学生类】字典(无锁) 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //遍历HashTable类(有锁) _SW.Restart(); for (int i = 0; i < _NUM; i++) { lock (_Dic) { _CurrentStudent = (Student)_HtClass[i]; } } _SW.Stop(); Console.WriteLine("遍历【HashTable学生类】字典(有锁) 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); Console.WriteLine("--------------------------------------------------------"); //遍历ConCurrent字典 _SW.Restart(); for (int i = 0; i < _NUM; i++) { _CurrentItem = _CctDic[i]; } _SW.Stop(); Console.WriteLine("遍历【ConCurrent字典】(字符串) 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); //遍历ConCurrent字典(类) _SW.Restart(); for (int i = 0; i < _NUM; i++) { _CurrentStudent = _CctDicClass[i]; } _SW.Stop(); Console.WriteLine("遍历【ConCurrent字典】(学生类) 花费时间为:{0} 毫秒", _SW.Elapsed.TotalMilliseconds); Console.WriteLine("--------------------------------------------------------"); _SW.Restart(); Console.WriteLine("-------------------结束---------------------------"); Console.ReadLine(); } }//Class_end public class Student { public string Name; public int Age; }}

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