#眉標=Windows Form
#副標=有趣的.NET記憶體管理探索
#大標=StringBuilder與String效能大車拼
#作者=文／圖	李明儒


==<反灰>===========
public class sample
{
    static void Main()
    {
        string s = "Hello" + " " + "World!";
        Console.WriteLine(s);
    }
}
==<end>==============



==<反灰>===========
Test1=4152ms
Test2=6ms
Test3=7ms
==<end>==============



==<box>===========
程式1 靜態字串串接比較
Stopwatch sw = new Stopwatch();
int times = 1000000;
sw.Start();
for (int i = 0; i < times; i++)
    GetSqlString_1();
sw.Stop();
Console.WriteLine(string.Format("Test1={0}ms", 
        sw.ElapsedMilliseconds));
sw.Reset();
sw.Start();
for (int i = 0; i < times; i++)
    GetSqlString_2();
sw.Stop();
Console.WriteLine(string.Format("Test2={0}ms", 
        sw.ElapsedMilliseconds));
sw.Reset();
sw.Start();
for (int i = 0; i < times; i++)
    GetSqlString_3();
sw.Stop();
Console.WriteLine(string.Format("Test3={0}ms", 
        sw.ElapsedMilliseconds));==<end>==============



==<box>====================
程式2
public class sample
{
    static void Main()
    {
        string s = "";
        s += "ABC";
        s += "123";
        return;
    }
}==<end>==============



============<box>===========
程式3
.load sos
extension C:\Windows\Microsoft.NET\Framework\v2.0.50727\sos.dll loaded
!clrstack -l
PDB symbol for mscorwks.dll not loaded
OS Thread Id: 0x28dc (10460)
ESP       EIP     
003feee4 00520094 sample.Main()
    LOCALS:
        <CLR reg> = 0x00000000
003ff13c 79e7c74b [GCFrame: 003ff13c] ==<end>==============




==<box>===========
程式4
!clrstack –l
OS Thread Id: 0x28dc (10460)
ESP       EIP     
003feee4 0052009c sample.Main()
    LOCALS:
        <CLR reg> = 0x015b1574

003ff13c 79e7c74b [GCFrame: 003ff13c] 

!dumpobj 0x015b1574
Name: System.String
MethodTable: 790fd8c4
EEClass: 790fd824
Size: 18(0x12) bytes
 (C:\Windows\assembly\GAC_32\mscorlib\2.0.0.0__b77a5c561934e089\mscorlib.dll)
String: 
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
79102290  4000096        4         System.Int32  1 instance        1 m_arrayLength
79102290  4000097        8         System.Int32  1 instance        0 m_stringLength
790ff328  4000098        c          System.Char  1 instance        0 m_firstChar
790fd8c4  4000099       10        System.String  0   shared   static Empty
    >> Domain:Value  005602e8:790d884c <<
7912dd40  400009a       14        System.Char[]  0   shared   static WhitespaceChars
    >> Domain:Value  005602e8:015b1440 <<

==<end>==============





==<box>===========
程式5
!clrstack -l
OS Thread Id: 0x28dc (10460)
ESP       EIP     
003feee4 005200ad sample.Main()
    LOCALS:
        <CLR reg> = 0x015c6590
(…略…)

!dumpobj 0x015c6590 (省略部分顯示內容)
Name: System.String
(...略…)
Size: 24(0x18) bytes
String: ABC
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
79102290  4000096        4         System.Int32  1 instance        4 m_arrayLength
79102290  4000097        8         System.Int32  1 instance        3 m_stringLength
790ff328  4000098        c          System.Char  1 instance       41 m_firstChar
(…略…)
	
==<end>==============





==<box>===========
程式6
!clrstack -l
(…略…)
    LOCALS:
        <CLR reg> = 0x015c65c0

!dumpobj 0x015c65c0
Name: System.String
(…略…)
Size: 30(0x1e) bytes
String: ABC123
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
79102290  4000096        4         System.Int32  1 instance        7 m_arrayLength
79102290  4000097        8         System.Int32  1 instance        6 m_stringLength
790ff328  4000098        c          System.Char  1 instance       41 m_firstChar
	==<end>==============




==<box>===========
程式7
public class sample
{
    static void Main()
    {
        StringBuilder sb = new StringBuilder();
        sb.Append("ABCD");
        sb.Append("1234");
        sb.Append("0123456789");
        return;
    }
}
	
==<end>==============




==<box>===========
程式8
!clrstack –l
(…略…)
    LOCALS:
        <CLR reg> = 0x013a65f0

!do 0x013a65f0
Name: System.Text.StringBuilder
(..略…)
Size: 20(0x14) bytes
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
791016bc  40000b1        8        System.IntPtr  1 instance 000CB688 m_currentThread
79102290  40000b2        c         System.Int32  1 instance 2147483647 m_MaxCapacity
790fd8c4  40000b3        4        System.String  0 instance 013a6604 m_StringValue

!do 013a6604
Name: System.String
(…略…)
Size: 50(0x32) bytes
 (C:\Windows\assembly\GAC_32\mscorlib\2.0.0.0__b77a5c561934e089\mscorlib.dll)
String: 
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
79102290  4000096        4         System.Int32  1 instance       17 m_arrayLength
79102290  4000097        8         System.Int32  1 instance        0 m_stringLength
790ff328  4000098        c          System.Char  1 instance        0 m_firstChar
	==<end>==============





==<box>===========
程式9
!do 013a6604
(…略…)
String: ABCD
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
79102290  4000096        4         System.Int32  1 instance       17 m_arrayLength
79102290  4000097        8         System.Int32  1 instance        4 m_stringLength
(…略…)

!do 013a6604
(…略…)
String: ABCD1234
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
79102290  4000096        4         System.Int32  1 instance       17 m_arrayLength
79102290  4000097        8         System.Int32  1 instance        8 m_stringLength
(…略…)
	
==<end>==============





==<box>===========
程式10
!do 0x013a65f0
Name: System.Text.StringBuilder
(…略…)
Size: 20(0x14) bytes
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
791016bc  40000b1        8        System.IntPtr  1 instance 00000000 m_currentThread
79102290  40000b2        c         System.Int32  1 instance 2147483647 m_MaxCapacity
790fd8c4  40000b3        4        System.String  0 instance 013a6778 m_StringValue
(…略…)

!do 013a6778
(…略…)
Size: 82(0x52) bytes
String: ABCD12340123456789
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
79102290  4000096        4         System.Int32  1 instance       33 m_arrayLength
79102290  4000097        8         System.Int32  1 instance       18 m_stringLength
(…略…)
	

==<end>==============





====<box>====================
程式11
public class sample
{
    static void test1() 
    {
        string s = "";
        for (int i = 1; i < 1024 * 64; i++)
            s += "0123456789ABCDEF";
        Console.WriteLine(s.Length);
    }
    static void test2()
    {
        StringBuilder sb = 
            new StringBuilder();
        for (int i = 1; i < 1024 * 64; i++)
            sb.Append("0123456789ABCDEF");
        Console.WriteLine(sb.Length);
    }
    static void test3()
    {
        StringBuilder sb = 
            new StringBuilder(1024 * 1024);
        for (int i = 1; i < 1024 * 64; i++)
            sb.Append("0123456789ABCDEF");
        Console.WriteLine(sb.Length);
    }
    static void Main()
    {
        System.Diagnostics.Stopwatch sw =
            new System.Diagnostics.Stopwatch();
        sw.Start();
        test1(); //or test2(), test3()
        sw.Stop();
        Console.WriteLine(sw.ElapsedMilliseconds);
        return; //Break here to !dumpheap -stat
    }

}
==<end>==============






==<box>===========
程式12
test1()
!dumpheap -stat
total 6689 objects
Statistics:
      MT    Count    TotalSize Class Name
791334a8        1           12 System.Collections.Generic.GenericEqualityComparer`1[[System.String, mscorlib]]
79119954        1           12 System.Security.Permissions.ReflectionPermission
…略…
004a05d0       14      2097044      Free
790fd8c4     5233      6585276 System.String
Total 6689 objects

test2()
!dumpheap -stat
total 6948 objects
Statistics:
      MT    Count    TotalSize Class Name
791334a8        1           12 System.Collections.Generic.GenericEqualityComparer`1[[System.String, mscorlib]]
79128334        1           12 System.Security.SecurityZone
…略…
7912d8f8      394        40076 System.Object[]
790fd8c4     5256      4491280 System.String
Total 6948 objects

test3()
!dumpheap -stat
total 6928 objects
Statistics:
      MT    Count    TotalSize Class Name
791334a8        1           12 System.Collections.Generic.GenericEqualityComparer`1[[System.String, mscorlib]]
79128334        1           12 System.Security.SecurityZone
…略…
7912d8f8      394        40076 System.Object[]
790fd8c4     5240      2393824 System.String
Total 6928 objects

==<end>==============
　　



==<box>===========
註解資料
1. 動態字串相加的效能比較：http://www.codeproject.com/KB/cs/stringperf.aspx。
2. @-Quoted String Literals：http://msdn2.microsoft.com/en-us/library/362314fe(VS.71).aspx。
3. SOS指令說明：http://msdn2.microsoft.com/en-us/library/bb190764(VS.80).aspx。
4. .NET記憶體配置概論：http://tinyurl.com/pnyo4。
==<end>==============