前一篇文章介绍了WinDbg入门,本篇主要介绍WinDbg常用命令和用法。

调试程序的CPU满载问题,关键是要知道程序当前正在进行什么操作。假如我们在cpu满载时创建了一个dump文件,使用下面几个命令可以查看当前程序正在进行什么处理: .time 运行.time命令会显示时间相关的信息,如系统运行时间,进程运行时间和CPU花费在内核态和用户态的时间。

0:000> .time
Debug session time: Tue Oct 23 08:38:35.000 2007 (GMT+1)
System Uptime: 4 days 17:48:01.906
Process Uptime: 0 days 0:24:37.000
  Kernel time: 0 days 0:04:23.000
  User time: 0 days 0:03:28.000

你可以看到系统已正常运行超过4天,进程运行了24分钟,CPU在内核态和用户态累积使用了8分钟。根据进程时间和CPU时间能大概估算出CPU使用率平均值是32.5%。

!threadpool

****通过!threadpool命令我们能准确知道创建dump时cpu的使用率。也能知道在队列中的待处理请求数,Completion Port(IOCP)线程数和定时器time数。

0:000> !threadpool
CPU utilization 100%
Worker Thread: Total: 5 Running: 4 Idle: 1 MaxLimit: 200 MinLimit: 2
Work Request in Queue: 16
Unknown Function: 6a2d945d  Context: 023ede30
Unknown Function: 6a2d945d  Context: 023ee1e8
AsyncTimerCallbackCompletion TimerInfo@11b53760
Unknown Function: 6a2d945d  Context: 023ee3a8
Unknown Function: 6a2d945d  Context: 023e3040
Unknown Function: 6a2d945d  Context: 023ee178
Unknown Function: 6a2d945d  Context: 023edfb0
AsyncTimerCallbackCompletion TimerInfo@11b36428
AsyncTimerCallbackCompletion TimerInfo@11b53868
Unknown Function: 6a2d945d  Context: 023ee060
Unknown Function: 6a2d945d  Context: 023ee290
Unknown Function: 6a2d945d  Context: 023eded0
Unknown Function: 6a2d945d  Context: 023edd88
Unknown Function: 6a2d945d  Context: 023ede98
Unknown Function: 6a2d945d  Context: 023ee258
Unknown Function: 6a2d945d  Context: 023edfe8
--------------------------------------
Number of Timers: 9
--------------------------------------
Completion Port Thread:Total: 3 Free: 3 MaxFree: 4 CurrentLimit: 2 MaxLimit: 200 MinLimit: 2

我们可以看到当前CPU已100%使用率,我们进入下一命令。

!runaway

这个命令用于显示所有正在运行的线程和它们的CPU使用率。这个命令对于查找高CPU使用率问题很有帮助!

0:000> !runaway
User Mode Time
  Thread       Time
  25:1a94      0 days 0:00:39.937
  16:1bc0      0 days 0:00:38.390
  50:1e8c      0 days 0:00:08.859
  52:1e40      0 days 0:00:08.687
  20:1c2c      0 days 0:00:08.234
  51:1340      0 days 0:00:08.171
  21:1bcc      0 days 0:00:06.953
  26:13ec      0 days 0:00:06.671
  44:131c      0 days 0:00:03.906
  22:d8c       0 days 0:00:03.375
  33:78c       0 days 0:00:02.656
  34:1a8c      0 days 0:00:00.906
  29:1f5c      0 days 0:00:00.828
   6:e28       0 days 0:00:00.625
   5:1c78      0 days 0:00:00.546
  23:14a4      0 days 0:00:00.484
   4:5ac       0 days 0:00:00.437
  45:5dc       0 days 0:00:00.421
   3:13b4      0 days 0:00:00.421
  47:19c8      0 days 0:00:00.375
  28:1b6c      0 days 0:00:00.250
  46:1dac      0 days 0:00:00.156
   7:1dd8      0 days 0:00:00.109
  48:cdc       0 days 0:00:00.093
  49:1eac      0 days 0:00:00.062
  15:1a64      0 days 0:00:00.062
   0:1804      0 days 0:00:00.046
  36:4a4       0 days 0:00:00.031
  11:1eb4      0 days 0:00:00.031
   1:10b4      0 days 0:00:00.031
  31:16ac      0 days 0:00:00.015
  14:4ac       0 days 0:00:00.015
   2:186c      0 days 0:00:00.015
  59:590       0 days 0:00:00.000
  58:294       0 days 0:00:00.000
  57:16d0      0 days 0:00:00.000
  56:1578      0 days 0:00:00.000
  55:1428      0 days 0:00:00.000
  54:16d8      0 days 0:00:00.000
  53:fd8       0 days 0:00:00.000
  43:1b8c      0 days 0:00:00.000
  42:1c24      0 days 0:00:00.000
  41:1e2c      0 days 0:00:00.000
  40:11b0      0 days 0:00:00.000
  39:edc       0 days 0:00:00.000
  38:1a08      0 days 0:00:00.000
  37:171c      0 days 0:00:00.000
  35:1254      0 days 0:00:00.000
  32:1f9c      0 days 0:00:00.000
  30:1ae8      0 days 0:00:00.000
  27:190c      0 days 0:00:00.000
  24:1d2c      0 days 0:00:00.000
  19:1e38      0 days 0:00:00.000
  18:ee4       0 days 0:00:00.000
  17:fb8       0 days 0:00:00.000
  13:1b54      0 days 0:00:00.000
  12:1a48      0 days 0:00:00.000
  10:f64       0 days 0:00:00.000
   9:1024      0 days 0:00:00.000
   8:1b78      0 days 0:00:00.000

你可以看到运行线程的总时间和使用.time命令看到的总cpu使用时间并不相等。原因很简单,因为线程被重复使用或回收了。这也意味着一个线程的CPU使用时间可能是处理多个请求的结果。

!threads

!threads显示当前所有的托管线程信息。输出如下:

0:000> !threads
ThreadCount: 48
UnstartedThread: 0
BackgroundThread: 29
PendingThread: 0
DeadThread: 19
Hosted Runtime: no
                                      PreEmptive   GC Alloc           Lock
  ID    OSID ThreadOBJ    State     GC       Context         Domain   Count APT Exception
  16    1 1bc0 001fccd0   1808220 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
  22    2  d8c 002016f0      b220 Enabled  00000000:00000000 0019daf0     0 MTA (Finalizer)
  14    4  4ac 00242e58   880a220 Enabled  00000000:00000000 0019daf0     0 MTA (Threadpool Completion Port)
  23    5 14a4 11b39f18    80a220 Enabled  00000000:00000000 0019daf0     0 MTA (Threadpool Completion Port)
  24    6 1d2c 11b41ad8      1220 Enabled  00000000:00000000 0019daf0     0 Ukn
  25    7 1a94 11b46c70   180b220 Enabled  27240c98:27241fd8 11b42540     1 MTA (Threadpool Worker)
  26    9 13ec 12ce2888   200b220 Enabled  2a9f1434:2a9f33c0 11b42540     0 MTA
  27    a 190c 12d85eb8   200b220 Enabled  00000000:00000000 11b42540     0 MTA
  29    b 1f5c 13df6a50   200b220 Enabled  2ab1da6c:2ab1f1c0 11b42540     0 MTA
  30    c 1ae8 12d44a58      b220 Enabled  00000000:00000000 11b42540     0 MTA
  31    d 16ac 12e2e008   200b220 Enabled  2a81348c:2a8153c0 11b42540     1 MTA
   5    e 1c78 12da2160       220 Enabled  00000000:00000000 0019daf0     0 Ukn
  33    8  78c 11b674c8   200b220 Enabled  2707b818:2707c1d8 11b42540     0 MTA
  34   12 1a8c 13f163c8       220 Enabled  00000000:00000000 0019daf0     0 Ukn
  36   13  4a4 13eef718   200b220 Enabled  2a7db4a4:2a7dd3c0 11b42540     0 MTA
   4   14  5ac 13ef2008       220 Enabled  00000000:00000000 0019daf0     0 Ukn
  42   10 1c24 13f0e950   880b220 Enabled  00000000:00000000 0019daf0     0 MTA (Threadpool Completion Port)
   6   11  e28 13f16008       220 Enabled  00000000:00000000 0019daf0     0 Ukn
   3    f 13b4 13eba008       220 Enabled  00000000:00000000 0019daf0     0 Ukn
  43   15 1b8c 140db008   880b220 Enabled  00000000:00000000 0019daf0     0 MTA (Threadpool Completion Port)
  44   17 131c 140ceb28   200b220 Enabled  272288c8:27229fd8 11b42540     0 MTA
  45   1d  5dc 140cd0a0       220 Enabled  00000000:00000000 0019daf0     0 Ukn
  47   20 19c8 1651a008       220 Enabled  00000000:00000000 0019daf0     0 Ukn
XXXX   24    0 16468880   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
  46   1f 1dac 1650ab48       220 Enabled  00000000:00000000 0019daf0     0 Ukn
XXXX   1a    0 140d5008   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   16    0 140c5008   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
  50    3 1e8c 14064420   180b220 Enabled  27246f54:27247fd8 11b42540     1 MTA (Threadpool Worker)
XXXX   35    0 1406e800   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
  51   36 1340 140df008   180b220 Enabled  2adec9cc:2aded1c0 11b42540     1 MTA (Threadpool Worker)
XXXX   37    0 16566868   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
  48   38  cdc 16578840       220 Enabled  00000000:00000000 0019daf0     0 Ukn
XXXX   39    0 16566c28   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   3b    0 1646b8b0   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   3c    0 16674008   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   3d    0 16676418   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   3e    0 16676fb8   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   3f    0 16674d48   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   40    0 1667de10   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   41    0 16680050   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   42    0 166812e8   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   43    0 16683e60   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
  52   44 1e40 165259e8   180b220 Enabled  2adf126c:2adf31c0 11b42540     1 MTA (Threadpool Worker)
XXXX   45    0 165b7c08   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   46    0 165aa3d8   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   47    0 165242c8   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
XXXX   48    0 165e9500   1801820 Enabled  00000000:00000000 0019daf0     0 Ukn (Threadpool Worker)
  49   3a 1eac 165676f0       220 Enabled  00000000:00000000 0019daf0     0 Ukn

线程ID为XXXX表示该线程已结束,并在等待回收。我们也能看到线程ID为22的线程正在终结(finalizer)。假如我们使用!runaway命令时看到22线程有大量的cpu活动,可能我们的程序有终结(finalizer)问题。

切换到指定线程

要切换到指定的线程,可以使用下面的格式命令:~[thread id]s,假如我们要切换到50线程,命令如下:

0:000> ~50s

现在我们已切换到线程50,可以使用很多其他有用的命令。

!clrstack !clrstack显示当前线程的堆栈信息,通过指定“-p”参数,还能看到方法调用的参数和局部变量信息。 下面是线程50的堆栈信息:

0:050> !clrstack
OS Thread Id: 0x1e8c (50)
ESP       EIP
17a9e750 7d61c828 [NDirectMethodFrameSlim: 17a9e750] System.DirectoryServices.Protocols.Wldap32.ldap_bind_s(IntPtr, System.String, System.DirectoryServices.Protocols.SEC_WINNT_AUTH_IDENTITY_EX, System.DirectoryServices.Protocols.BindMethod)
17a9e768 14df70f9 System.DirectoryServices.Protocols.LdapConnection.BindHelper(System.Net.NetworkCredential, Boolean)
17a9e794 14df6de0 System.DirectoryServices.Protocols.LdapConnection.Bind()
17a9e79c 14df59e9 System.DirectoryServices.Protocols.LdapConnection.SendRequestHelper(System.DirectoryServices.Protocols.DirectoryRequest, Int32 ByRef)
17a9e8b8 14df56e8 System.DirectoryServices.Protocols.LdapConnection.SendRequest(System.DirectoryServices.Protocols.DirectoryRequest, System.TimeSpan)
17a9e8bc 14df5657 [InlinedCallFrame: 17a9e8bc]

从下向上看,我们能知道LdapConnection调用了SendRequest方法,而SendRequest又调用了SendRequestHelper方法等等。 如果我们执行“!clrstack -p”命令,我们得到信息:

0:050> !clrstack -p
OS Thread Id: 0x1e8c (50)
ESP       EIP
17a9e750 7d61c828 [NDirectMethodFrameSlim: 17a9e750] System.DirectoryServices.Protocols.Wldap32.ldap_bind_s(IntPtr, System.String, System.DirectoryServices.Protocols.SEC_WINNT_AUTH_IDENTITY_EX, System.DirectoryServices.Protocols.BindMethod)
17a9e768 14df70f9 System.DirectoryServices.Protocols.LdapConnection.BindHelper(System.Net.NetworkCredential, Boolean)
    PARAMETERS:
        this = 0x271fdfe0
        newCredential =
        needSetCredential =

17a9e794 14df6de0 System.DirectoryServices.Protocols.LdapConnection.Bind()
    PARAMETERS:
        this =

17a9e79c 14df59e9 System.DirectoryServices.Protocols.LdapConnection.SendRequestHelper(System.DirectoryServices.Protocols.DirectoryRequest, Int32 ByRef)
    PARAMETERS:
        this = 0x271fdfe0
        request = 0x27246e38
        messageID = 0x17a9e8ec

17a9e8b8 14df56e8 System.DirectoryServices.Protocols.LdapConnection.SendRequest(System.DirectoryServices.Protocols.DirectoryRequest, System.TimeSpan)
    PARAMETERS:
        this = 0x271fdfe0
        request = 0x27246e38
        requestTimeout =

17a9e8bc 14df5657 [InlinedCallFrame: 17a9e8bc]

我们可以看到DirectoryRequest参数传递给了SendRequest和SendRequestHelper,要查看DirectoryRequest的相关信息,我们只需复制它的地址(0x27246e38),并在下个命令中使用。

!dumpobject (!do) 这是另外一个重要的命令。Dumpobject会打印出指定地址的对象的相关信息。我们使用刚才的地址试下:

0:050> !do 0x27246e38
Name: System.DirectoryServices.Protocols.SearchRequest
MethodTable: 14b394c4
EEClass: 14d97ce0
Size: 52(0x34) bytes
GC Generation: 0
(C:\WINDOWS\assembly\GAC_MSIL\System.DirectoryServices.Protocols\2.0.0.0__b03f5f7f11d50a3a\System.DirectoryServices.Protocols.dll)
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
02c39310  4000102        4        System.String  0 instance 00000000 directoryRequestID
14b398bc  4000103        8 ...ControlCollection  0 instance 27246e90 directoryControlCollection
02c39310  4000111        c        System.String  0 instance 27246d00 dn
12579f5c  4000112       10 ....StringCollection  0 instance 27246eb4 directoryAttributes
02c36ca0  4000113       14        System.Object  0 instance 27246ddc directoryFilter
14b39344  4000114       18         System.Int32  1 instance        1 directoryScope
14b393fc  4000115       1c         System.Int32  1 instance        0 directoryRefAlias
0fd3da00  4000116       20         System.Int32  1 instance        0 directorySizeLimit
1202af88  4000117       28      System.TimeSpan  1 instance 27246e60 directoryTimeLimit
120261c8  4000118       24       System.Boolean  1 instance        0 directoryTypesOnly

通过打印的信息,可以知道它是System.DirectoryServices.Protocols.SearchRequest的一个对象,而显示的都是 System.DirectoryServices.Protocols.SearchRequest的属性值。要知道SearchRequest类的相关属性信息,可以查看MSDN。当前我们已有RequestId, Scope和DistinguishedName等等。 所以,假如我们想知道SearchRequest对象的DistinguishedName属性值,即是上面列表中的dn,我们只需再复制它的地址(27246d00),并再次使用!dumpobject命令。因为DistinguishedName是System.String类型,所以输出结果很明显:

0:050> !do 27246d00
Name: System.String
MethodTable: 02c39310
EEClass: 0fb610ac
Size: 112(0x70) bytes
GC Generation: 0
(C:\WINDOWS\assembly\GAC_32\mscorlib\2.0.0.0__b77a5c561934e089\mscorlib.dll)
String: CN=Dummy,CN=Accounts,CN=useradm,DC=dummy,DC=net
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
0fd3da00  4000096        4         System.Int32  1 instance       48 m_arrayLength
0fd3da00  4000097        8         System.Int32  1 instance       47 m_stringLength
0fb80010  4000098        c          System.Char  1 instance       43 m_firstChar
02c39310  4000099       10        System.String  0   shared   static Empty
    >> Domain:Value  0019daf0:03380310 11b42540:03380310 << 0fb86d44  400009a       14        System.Char[]  0   shared   static WhitespaceChars     >> Domain:Value  0019daf0:03380324 11b42540:033855bc <<

通过输出的信息我们很容易知道DistinguishedName属性的值是“CN=Dummy,CN=Accounts,CN=useradm,DC=dummy,DC=net”。如果我们想查看更多内容,只需继续使用!dumpobject命令即可。

!dumpstackobjects (!dso) 使用该命令我们可以查看到当前线程的堆栈引用的所有托管对象。打印信息如下:

0:050> !dso
OS Thread Id: 0x1e8c (50)
ESP/REG  Object   Name
17a9e534 0741f860 System.RuntimeType
17a9e6b8 271fdfe0 System.DirectoryServices.Protocols.LdapConnection
17a9e6bc 27246f20 System.DirectoryServices.Protocols.SEC_WINNT_AUTH_IDENTITY_EX
17a9e740 271fdfe0 System.DirectoryServices.Protocols.LdapConnection
17a9e744 27246f20 System.DirectoryServices.Protocols.SEC_WINNT_AUTH_IDENTITY_EX
17a9e764 27246f20 System.DirectoryServices.Protocols.SEC_WINNT_AUTH_IDENTITY_EX
17a9e768 271fdfe0 System.DirectoryServices.Protocols.LdapConnection
17a9e780 271fdfe0 System.DirectoryServices.Protocols.LdapConnection
17a9e784 27246e38 System.DirectoryServices.Protocols.SearchRequest
17a9e794 271fdf14 System.DirectoryServices.Protocols.LdapDirectoryIdentifier
17a9e7a8 27246ef8 System.Collections.ArrayList
17a9e7bc 27246ef8 System.Collections.ArrayList
17a9e7c8 271fdfe0 System.DirectoryServices.Protocols.LdapConnection
17a9e8a4 27246e38 System.DirectoryServices.Protocols.SearchRequest
17a9e8d0 27246ed8 System.Object[]    (System.Object[])
17a9e8e0 073ff6b8 System.String    cn
17a9e8e4 271fdfe0 System.DirectoryServices.Protocols.LdapConnection
17a9e8f4 27246d00 System.String    CN=Dummy,CN=Accounts,CN=useradm,DC=Dummy,DC=net
17a9e8f8 271fdfe0 System.DirectoryServices.Protocols.LdapConnection
17a9e8fc 27246e38 System.DirectoryServices.Protocols.SearchRequest
17a9e910 03380310 System.String
17a9e914 27246e24 System.Object[]    (System.String[])
17a9e918 272399a8 System.String    CN=OID-Dummy-ABC123,CN=Dummy,CN=Accounts,CN=useradm,DC=Dummy,DC=net
17a9e91c 27246ddc System.String    (CN=OID-Dummy-ABC123)
...etc...

这个命令对于查找当前线程引用了那些对象很有用。假如你想查看某一对象,只需复制[Object]字段的地址,并使用 !dumpobject命令:

0:050> !do 271fdfe0
Name: System.DirectoryServices.Protocols.LdapConnection
MethodTable: 14a2040c
EEClass: 149daf08
Size: 56(0x38) bytes
(C:\WINDOWS\assembly\GAC_MSIL\System.DirectoryServices.Protocols\2.0.0.0__b03f5f7f11d50a3a\System.DirectoryServices.Protocols.dll)
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
14a2078c  40000c3        4 ...NetworkCredential  0 instance 00000000 directoryCredential
14a2144c  40000c4        8 ...ificateCollection  0 instance 271fe018 certificatesCollection
1202af88  40000c5       10      System.TimeSpan  1 instance 271fdff0 connectionTimeOut
1466fe50  40000c6        c ...rectoryIdentifier  0 instance 271fdf14 directoryIdentifier
14a2034c  4000236       24         System.Int32  0 instance        2 connectionAuthType
14a223a4  4000237       18 ...dapSessionOptions  0 instance 271fe2d8 options
0fb896d8  4000238       28        System.IntPtr  0 instance 564180944 ldapHandle
120261c8  4000239       2c       System.Boolean  0 instance        0 disposed
120261c8  400023a       2d       System.Boolean  0 instance        0 bounded
120261c8  400023b       2e       System.Boolean  0 instance        0 needRebind
14a22084  400023e       1c ...pResponseCallback  0 instance 271fe03c fd
120261c8  4000243       2f       System.Boolean  0 instance        0 setFQDNDone
120261c8  4000244       30       System.Boolean  0 instance        1 automaticBind
120261c8  4000245       31       System.Boolean  0 instance        1 needDispose
120261c8  4000246       32       System.Boolean  0 instance        1 connected
14a2267c  4000247       20 ...s.QUERYCLIENTCERT  0 instance 271fe394 clientCertificateRoutine
0fd314bc  400023c       20 ...ections.Hashtable  0   shared   static handleTable
    >> Domain:Value  0019daf0:NotInit  11b42540:073fe504 < <
02c36ca0  400023d       24        System.Object  0   shared   static objectLock
    >> Domain:Value  0019daf0:NotInit  11b42540:073fe53c < <
0fd314bc  400023f       28 ...ections.Hashtable  0   shared   static asyncResultTable
    >> Domain:Value  0019daf0:NotInit  11b42540:073fe610 < <
14a21864  4000240       2c ...lResultsProcessor  0   shared   static partialResultsProcessor
    >> Domain:Value  0019daf0:NotInit  11b42540:073fe678 < <
12305e94  4000241       30 ....ManualResetEvent  0   shared   static waitHandle
    >> Domain:Value  0019daf0:NotInit  11b42540:073fe64c < <
14a21954  4000242       34 ...lResultsRetriever  0   shared   static retriever
    >> Domain:Value  0019daf0:NotInit  11b42540:073fe6a8 < <

!dumparray (!da) 你可能已经注意到有很多对象数组在堆栈中,在上面的列表中查找System.Object[]类型就能找到。如果你对对象数组使用 !dumpobject命令,你只能看到数组信息,而不能看到数组的内容信息,要看到数组内容信息,就需要使用!dumparray命令,或简称!da:

0:050> !do 27239b98
Name: System.Object[]
MethodTable: 02c3896c
EEClass: 02c388ec
Size: 24(0x18) bytes
Array: Rank 1, Number of elements 2, Type CLASS
Element Type: System.String
Fields:
None

0:050> !da 27239b98
Name: System.String[]
MethodTable: 02c3896c
EEClass: 02c388ec
Size: 24(0x18) bytes
Array: Rank 1, Number of elements 2, Type CLASS
Element Methodtable: 02c39310
[0] 272399a8
[1] 27239a44

通过!dumparray命令我们能知道该数组对象是字符串数组,并给出了数组项的地址。再使用!dumpobject命令我们就能看到数组项的具体内容。

!objsize 如果你查看上面打印的信息,可以看到对象的大小是24字节。从某方面来说,这是对的,24字节是System.Object[]数组对象本身大小,但并不包括数组内容的大小!要获得整个对象的大小,就要使用到 !objsize命令:

0:050> !objsize 27239b98
sizeof(27239b98) =          348 (       0x15c) bytes (System.Object[])

!objsize会遍历对象引用的所有子对象,并计算出总的大小。如上面数组对象和它的内容的总大小是348字节。 如果对象有引用很多子对象,那么!objsize会花费较多的时间计算出总大小。

!dumpheap 这是另一个较频繁使用的命令。!dumpheap会打印出所有在托管堆中的对象信息。直接执行该命令会打印出大量的信息,所以一般使用时都至少带上一个参数。加上-stat参数后会输出总结后的信息,如下面是截取的是!dumpheap -stat命令输出的一部分:

0:050> !dumpheap -stat
------------------------------
Heap 0
total 2754508 objects
------------------------------
Heap 1
total 2761329 objects
------------------------------
total 5515837 objects
Statistics:
      MT    Count    TotalSize Class Name
16e0a6d8        1           12 System.Collections.Generic.ObjectEqualityComparer`1[[System.Data.ProviderBase.DbConnectionInternal, System.Data]]
16d9cd9c        1           12 System.Xml.Serialization.Configuration.DateTimeSerializationSection+DateTimeSerializationMode
16d9bf30        1           12 System.Diagnostics.OrdinalCaseInsensitiveComparer
16d9112c        1           12 System.Xml.Serialization.NameTable
16d7f664        1           12 System.Xml.Serialization.TempAssemblyCache
163ea85c        1           12 System.Data.Res
1501e4c4        1           12 System.Collections.Generic.ObjectEqualityComparer`1[[System.Web.UI.Control, System.Web]]
14efb138        1           12 System.Net.TimeoutValidator
14ef9964        1           12 System.Net.Cache.HttpRequestCacheLevel
14ef77a8        1           12 Microsoft.Win32.WinInetCache
14ef68e4        1           12 System.Net.WebRequest+WebProxyWrapper
14ef658c        1           12 System.Net.Configuration.ProxyElement+BypassOnLocalValues
14ef63d8        1           12 System.Net.Configuration.ProxyElement+AutoDetectValues
14ef5b68        1           12 System.Net.CaseInsensitiveAscii
14ef5610        1           12 System.Net.HeaderInfoTable
14ef4718        1           12 System.Net.HttpRequestCreator
14db6710        1           12 System.Web.Configuration.MachineKeyValidationConverter
14db3140        1           12 System.Collections.Generic.ObjectEqualityComparer`1[[System.Runtime.Serialization.MemberHolder, mscorlib]]
14b3f4d8        1           12 System.Web.UI.SupportsEventValidationAttribute
...etc...
14a276a8    19578       704808 System.DirectoryServices.Interop.AdsValueHelper
14a2ea24     9196       735680 System.Web.UI.WebControls.Label
14a2e51c    16862       741928 System.Web.UI.WebControls.Style
125778ec    48015       768240 System.Collections.Specialized.NameObjectCollectionBase+NameObjectEntry
120261c8    65842       790104 System.Boolean
14a2ee7c     9198       809424 System.Web.UI.WebControls.Table
14b311c4     9647       810348 System.Web.UI.WebControls.Image
13a2b7dc    34913       837912 System.Web.HttpServerVarsCollectionEntry
14b303a4    10605       848400 System.Web.UI.WebControls.HyperLink
14d8e3d4    77748       932976 Microsoft.Web.UI.WebControls.BaseChildNodeCollection+ActionType
14db90ac    81372       976464 System.Web.UI.WebControls.FontInfo
14b30694    28648      1031328 System.Web.UI.WebControls.TableRow+CellControlCollection
14d8fdbc    38912      1089536 Microsoft.Web.UI.WebControls.TreeNodeCollection
14b3d0bc    86592      1385472 System.Web.UI.Pair
1466c5c4    39305      1414980 System.Web.UI.ControlCollection
14d8e48c    77748      1865952 Microsoft.Web.UI.WebControls.BaseChildNodeCollection+Action
1545061c    38874      2176944 Microsoft.Web.UI.WebControls.TreeNode
14b30eec    52668      2317392 System.Web.UI.WebControls.TableItemStyle
14a2f804    28515      2395260 System.Web.UI.WebControls.TableRow
14a2be6c    40894      2453640 System.Web.UI.LiteralControl
0fd3da00   228792      2745504 System.Int32
14b3e3ac   244793      2937516 System.Web.UI.IndexedString
14a2de94   198580      3177280 System.Web.UI.StateBag
1466c454    80512      3542528 System.Web.UI.Control+OccasionalFields
12302c2c   205849      4116980 System.Collections.Specialized.HybridDictionary
14b30024    52934      4446456 System.Web.UI.WebControls.TableCell
12302f2c   178294      4992232 System.Collections.Specialized.ListDictionary
14a2e284   412762      6604192 System.Web.UI.StateItem
14d8ce64   117078      7024680 Microsoft.Web.UI.WebControls.CssCollection
0fd314bc   132065      7395640 System.Collections.Hashtable
1230319c   422580      8451600 System.Collections.Specialized.ListDictionary+DictionaryNode
1202a58c   380438      9130512 System.Collections.ArrayList
0fd32050   133000     22582944 System.Collections.Hashtable+bucket[]
02c3896c   649842     23275900 System.Object[]
0fd3c12c     3471     36385536 System.Byte[]
001fee20      338     65409920      Free
02c39310   683083    161821000 System.String
Total 5515837 objects
Fragmented blocks larger than 0.5 MB:
    Addr     Size      Followed by
2adf31cc    2.0MB         2aff85d8 System.String
2b006a2c   20.3MB         2c4530d8 System.Net.SocketAddress

输出信息按对象类型的总大小升序排序,你一般可以在列表的最下面找到string对象的大小,因为字符串在程序中一般是最常用的。 其他比较有用的参数是-type和-mt(MethodTable的意思)。使用它们你可以查看指定对象类型的详细信息,例如假如我们想查看System.Net.HttpRequestCreator类型的具体信息,可以复制上面列表中它的MT字段地址(14ef4718),然后使用 !dumpheap -mt命令:

0:050> !dumpheap -mt 14ef4718
------------------------------
Heap 0
Address       MT     Size
0342ccf8 14ef4718       12
total 1 objects
------------------------------
Heap 1
Address       MT     Size
total 0 objects
------------------------------
total 1 objects
Statistics:
      MT    Count    TotalSize Class Name
14ef4718        1           12 System.Net.HttpRequestCreator

上面列出了所有System.Net.HttpRequestCreator类型的对象的地址,假如我们想查看指定对象的信息,再使用!dumpobject命令就可以了。 !dumpheap -type可以根据字符串来匹配对应的对象类型。如我们输入命令“!dumpheap -type System.Web”,是指显示所有类名包含有“System.Web”字符串的对象信息。 其他参数-min和-max是接受表示对象大小的最大值和最小值(单位字节),命令会只列出大于指定值或小于指定值的对象信息。这两个参数对于查找滥用字符串问题很有帮助。

实战训练 查明缓存使用的大小 为了知道在System.Web.Caching.Cache类型中有多少数据,我执行了“ !dumpheap -stat -type System.Web.Caching.Cache”命令。注意,我用了-stat参数,否则我会得到一个包含有System.Web.Caching.CacheKeys和System.Web.Caching.CacheEntrys对象的很长的列表。下面的执行结果:

0:050> !dumpheap -type System.Web.Caching.Cache -stat
------------------------------
Heap 0
total 665 objects
------------------------------
Heap 1
total 1084 objects
------------------------------
total 1749 objects
Statistics:
      MT    Count    TotalSize Class Name
123056f8        1           12 System.Web.Caching.CacheKeyComparer
1230494c        1           12 System.Web.Caching.Cache
1230500c        1           24 System.Web.Caching.CacheMultiple
1230514c        1           32 System.Web.Caching.CacheMemoryStats
123053b4        1           36 System.Web.Caching.CacheMemoryTotalMemoryPressure
123059bc        2           40 System.Web.Caching.CacheUsage
12304bdc        1           48 System.Web.Caching.CacheCommon
123054f4        1           52 System.Web.Caching.CacheMemoryPrivateBytesPressure
12305874        2           64 System.Web.Caching.CacheExpires
12304e64        2          200 System.Web.Caching.CacheSingle
1255b594       85         1360 System.Web.Caching.CacheDependency+DepFileInfo
123046c4       40         1440 System.Web.Caching.CacheDependency
123042ec       47         1504 System.Web.Caching.CacheItemRemovedCallback
123063fc      832        16640 System.Web.Caching.CacheKey
12306820      732        52704 System.Web.Caching.CacheEntry
Total 1749 objects

很明显System.Web.Caching.Cache的方法列表地址(MethodTable)是1230494c,再使用!dumpheap命令我就能看到它的所有对象信息,如下:

0:050> !dumpheap -mt 1230494c
------------------------------
Heap 0
Address       MT     Size
03392d20 1230494c       12
total 1 objects
------------------------------
Heap 1
Address       MT     Size
total 0 objects
------------------------------
total 1 objects
Statistics:
      MT    Count    TotalSize Class Name
1230494c        1           12 System.Web.Caching.Cache
Total 1 objects

可以看到System.Web.Caching.Cache类型只有一个对象,地址是03392d20,再通过!objsize命令就能计算出它的大小。因为缓存对象很复杂,并包含有大量的子对象,要计算出总大小需要花些时间:

0:050> !objsize 03392d20
sizeof(03392d20) =    266640828 (   0xfe49dbc) bytes (System.Web.Caching.Cache)

所以缓存的总大小是 266 MB。

缓存了什么东西? 为了弄清缓存中保存了什么内容,我查看了System.Web.Caching.CacheEntry的对象信息。通过之前的信息可以知道System.Web.Caching.CacheEntry类型的方法列表(MethodTable)是12306820。执行!dumpheap命令取CacheEntry的所有对象信息:

0:050> !dumpheap -mt 12306820
------------------------------
Heap 0
Address       MT     Size
033950bc 12306820       72
033a20d8 12306820       72
033ac79c 12306820       72
033da21c 12306820       72
033f04c4 12306820       72
03428ec8 12306820       72
0344dab4 12306820       72
03815d00 12306820       72
038265d8 12306820       72
....etc...
03af7010 12306820       72
03b291bc 12306820       72
03b2c674 12306820       72
03b6dca0 12306820       72
03b797dc 12306820       72
03b85318 12306820       72
03ba9150 12306820       72
03c258cc 12306820       72
03de43c8 12306820       72
03e160f8 12306820       72
total 382 objects
------------------------------
total 732 objects

要显示上面的信息,也可以使用“!dumpheap -type System.Web.Caching.CacheEntry”命令。 有了所有CacheEntry对象的地址信息,我随机拿了一个地址查看它的内容:

0:050> !do 03b2c674
Name: System.Web.Caching.CacheEntry
MethodTable: 12306820
EEClass: 122f6470
Size: 72(0x48) bytes
(C:\WINDOWS\assembly\GAC_32\System.Web\2.0.0.0__b03f5f7f11d50a3a\System.Web.dll)
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
02c39310  4001327        4        System.String  0 instance 03b2c600 _key
0fb8f1f8  4001328        c          System.Byte  0 instance        2 _bits
0fd3da00  4001329        8         System.Int32  0 instance -1314181915 _hashCode
02c36ca0  4001330       10        System.Object  0 instance 03b2c644 _value
120219d0  4001331       1c      System.DateTime  1 instance 03b2c690 _utcCreated
120219d0  4001332       24      System.DateTime  1 instance 03b2c698 _utcExpires
1202af88  4001333       2c      System.TimeSpan  1 instance 03b2c6a0 _slidingExpiration
0fb8f1f8  4001334        d          System.Byte  0 instance        7 _expiresBucket
123062d8  4001335       34 ...g.ExpiresEntryRef  1 instance 03b2c6a8 _expiresEntryRef
0fb8f1f8  4001336        e          System.Byte  0 instance 4294967295 _usageBucket
12306738  4001337       38 ...ing.UsageEntryRef  1 instance 03b2c6ac _usageEntryRef
120219d0  4001338       3c      System.DateTime  1 instance 03b2c6b0 _utcLastUpdate
123046c4  4001339       14 ...g.CacheDependency  0 instance 00000000 _dependency
02c36ca0  400133a       18        System.Object  0 instance 033d8344 _onRemovedTargets
120219d0  400132d      1bc      System.DateTime  1   shared   static NoAbsoluteExpiration
    >> Domain:Value  0019daf0:NotInit  11b42540:03395104 < <
1202af88  400132e      1c0      System.TimeSpan  1   shared   static NoSlidingExpiration
    >> Domain:Value  0019daf0:NotInit  11b42540:03395114 < <
1202af88  400132f      1c4      System.TimeSpan  1   shared   static OneYear
    >> Domain:Value  0019daf0:NotInit  11b42540:03395124 < <

输出的是CacheEntry的属性信息,里面最重要的是_value属性。我复制它的地址(03b2c644),再用!dumpobject命令查看:

0:000> !do 03e160c8
Name: System.Web.SessionState.InProcSessionState
MethodTable: 14dbad5c
EEClass: 14e43af8
Size: 48(0x30) bytes
(C:\WINDOWS\assembly\GAC_32\System.Web\2.0.0.0__b03f5f7f11d50a3a\System.Web.dll)
Fields:
      MT    Field   Offset                 Type VT     Attr    Value Name
1466c9d8  4001d89        4 ...ateItemCollection  0 instance 1a7f5438 _sessionItems
1292672c  4001d8a        8 ...ObjectsCollection  0 instance 00000000 _staticObjects
0fd3da00  4001d8b        c         System.Int32  0 instance       20 _timeout
120261c8  4001d8c       18       System.Boolean  0 instance        0 _locked
120219d0  4001d8d       1c      System.DateTime  1 instance 03e160e4 _utcLockDate
0fd3da00  4001d8e       10         System.Int32  0 instance        1 _lockCookie
1202bf60  4001d8f       24 ...ReadWriteSpinLock  1 instance 03e160ec _spinLock
0fd3da00  4001d90       14         System.Int32  0 instance        0 _flags

可以看到缓存的是一个InProcSessionState对象。

参考文章: Getting started with windbg - part I

Getting started with windbg - part II