C#並發容器之ConcurrentDictionary與普通Dictionary帶鎖性能詳解
結果已經寫在註釋中
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
//對於寫入操作並發詞典要比普通帶鎖詞典要慢
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
//對於讀取操作並發詞典要比普通帶鎖詞典要快
//concurrentDictionary采用細粒度鎖定[fine-grained locking]
//普通帶鎖dictionary采用粗粒度鎖定[coarse-grained locking]
//在多核多線程的情況下concurrentDictionary將有更好的性能表現
sw.Restart();
Console.ReadKey();
}
const string Item = "Dictionary item";
public static string CurrentItem;
補充：C#中普通字典（Dictionary）、並發字典（ConcurrentDictionary）、和哈希表（Hashtable）讀寫性能比較
一、說明
程序有時候需要並發多線程操作，多線程讀取同一個容器內的東西是可以的，但是如果需要修改及寫入到同一容器內，會有索引失敗的問題，即兩個進程同時向同一個位置寫入內容，這種情況下需要通過lock（var），將容器鎖定，也可以直接使用可並發讀寫的容器（ConcurrentDictionary）
測試分2部分，一次是寫入操作，包含帶鎖寫入和不帶鎖寫入，其中每個裡面又細分為寫入字符串和寫入一個類，還有一次是遍歷操作，同樣包含帶鎖讀和不帶鎖讀，其中也分為讀取字符串和讀取類。
二、測試結果
2.1、寫入用時
2.2、遍歷用時
2.3、結論
對於寫入操作速度：普通詞典 > HashTable > 並發詞典
對於讀操作速度：並發字典 > 帶鎖字典 > HashTable
無論普通字典還是HashTable，帶鎖花費的時間都要比不帶鎖慢，為瞭線程安全，肯定要犧牲時間的。
所以如果需要自己寫入的話，推薦帶鎖普通字典，讀寫速度都很均衡。
三、測試代碼如下
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;//執行次數
Student _CurrentStudent = null;
Student student = new Student { Name = _Item, Age = 23 };
Stopwatch _SW = new Stopwatch();
//字符串寫入字典（無鎖）
_SW.Start();
for (int i = 0; i < _NUM; i++)
{
_Dic[i] = _Item;
}
_SW.Stop();
Console.WriteLine("向字典寫入【字符串】不添加鎖（Lock）花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//字符串寫入字典（有鎖）
_Dic = new Dictionary<int, string>();
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
lock (_Dic)
{
_Dic[i] = _Item;
}
}
_SW.Stop();
Console.WriteLine("向字典寫入【字符串】添加鎖（Lock）花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//類寫入字典（無鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
_DicClass[i] = student;
}
_SW.Stop();
Console.WriteLine("向子典寫入【學生類】不添加鎖（Lock）花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//類寫入字典（有鎖）
_DicClass = new Dictionary<int, Student>();
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
lock (_DicClass)
{
_DicClass[i] = student;
}
}
_SW.Stop();
Console.WriteLine("向子典寫入【學生類】添加鎖（Lock）花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
Console.WriteLine("----------------------------------------------------");
//字符串寫入HashTable（無鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
_Ht[i] = _Item;
}
_SW.Stop();
Console.WriteLine("向HashTable寫入【字符串】不添加鎖（Lock）花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//字符串寫入HashTable（有鎖）
_Ht = new Hashtable();
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
lock (_Ht)
{
_Ht[i] = _Item;
}
}
_SW.Stop();
Console.WriteLine("向HashTable寫入【字符串】添加鎖（Lock）花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//類寫入HashTable（無鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
_HtClass[i] = student;
}
_SW.Stop();
Console.WriteLine("向HashTable寫入【學生類】不添加鎖（Lock）花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//類寫入HashTable（有鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
lock (_HtClass)
{
_HtClass[i] = student;
}
}
_SW.Stop();
Console.WriteLine("向HashTable寫入【學生類】添加鎖（Lock）花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
Console.WriteLine("----------------------------------------------------------");
//字符串寫入ConcurrentDictionary
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
_CctDic[i] = _Item;
}
_SW.Stop();
Console.WriteLine("向ConcurrentDictionary寫入【字符串】 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//類寫入ConcurrentDictionary
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
_CctDicClass[i] = student;
}
_SW.Stop();
Console.WriteLine("向ConcurrentDictionary寫入【學生類】 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
Console.WriteLine("--------------------------------------------------------");
//遍歷普通字典（無鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
_CurrentItem = _Dic[i];
}
_SW.Stop();
Console.WriteLine("遍歷【普通】字典（無鎖） 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//遍歷普通字典（有鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
lock (_Dic)
{
_CurrentItem = _Dic[i];
}
}
_SW.Stop();
Console.WriteLine("遍歷【普通】字典（有鎖） 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//遍歷類字典（無鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
_CurrentStudent = _DicClass[i];
}
_SW.Stop();
Console.WriteLine("遍歷【學生類】字典（無鎖） 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//遍歷類字典（有鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
lock (_Dic)
{
_CurrentStudent = _DicClass[i];
}
}
_SW.Stop();
Console.WriteLine("遍歷【學生類】字典（有鎖） 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
Console.WriteLine("--------------------------------------------------------");
//遍歷HashTable（無鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
_CurrentItem = _Ht[i].ToString();
}
_SW.Stop();
Console.WriteLine("遍歷【HashTable】字典（無鎖） 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//遍歷HashTable（有鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
lock (_Dic)
{
_CurrentItem = _Ht[i].ToString();
}
}
_SW.Stop();
Console.WriteLine("遍歷【HashTable】字典（有鎖） 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//遍歷HashTable類（無鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
_CurrentStudent = (Student)_HtClass[i];
}
_SW.Stop();
Console.WriteLine("遍歷【HashTable學生類】字典（無鎖） 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//遍歷HashTable類（有鎖）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
lock (_Dic)
{
_CurrentStudent = (Student)_HtClass[i];
}
}
_SW.Stop();
Console.WriteLine("遍歷【HashTable學生類】字典（有鎖） 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
Console.WriteLine("--------------------------------------------------------");
//遍歷ConCurrent字典
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
_CurrentItem = _CctDic[i];
}
_SW.Stop();
Console.WriteLine("遍歷【ConCurrent字典】（字符串） 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
//遍歷ConCurrent字典（類）
_SW.Restart();
for (int i = 0; i < _NUM; i++)
{
_CurrentStudent = _CctDicClass[i];
}
_SW.Stop();
Console.WriteLine("遍歷【ConCurrent字典】（學生類） 花費時間為:{0} 毫秒", _SW.Elapsed.TotalMilliseconds);
Console.WriteLine("--------------------------------------------------------");
_SW.Restart();
Console.WriteLine("-------------------結束---------------------------");
Console.ReadLine();
}
}//Class_end
public class Student
{
public string Name;
public int Age;
}
}
以上為個人經驗，希望能給大傢一個參考，也希望大傢多多支持WalkonNet。如有錯誤或未考慮完全的地方，望不吝賜教。
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