[20190419]shared latch spin count 2.txt

--//上午測試shared latch XX模式的情況,連結:http://blog.itpub.net/267265/viewspace-2641902/

--//繼續測試其它情況.

--//連結:

S mode get X mode get

Held in S mode Compatible 2*_spin_count

Held in X mode 0 2*_spin_count

Blocking mode 0 2*_spin_count

1.環境:

SCOTT@book> @ ver1

PORT_STRING VERSION BANNER

------------------------------ -------------- --------------------------------------------------------------------------------

x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

SYS@book> @ hide spin_count

NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE

----------------- ---------------------------------- ------------- ------------- ------------

_mutex_spin_count Mutex spin count TRUE 255 255

_spin_count Amount to spin waiting for a latch TRUE 2000 2000

$ cat shared_latch.txt

/* 引數如下: @ latch.txt latch_name willing why where mode sleep_num */

--//connect / as sysdba

col laddr new_value laddr

col vmode new_value vmode

select decode(lower('&&5'),'s',8,'x',16,'8',8,'16',16) vmode from dual ;

SELECT addr laddr FROM v$latch_parent WHERE NAME='&&1';

oradebug setmypid

oradebug call kslgetsl_w 0x&laddr &&2 &&3 &&4 &vmode

host sleep &&6

oradebug call kslfre 0x&laddr

--//exit

--//注:我前幾天的測試指令碼有connect / as sysdba,exit這兩行,我為了調式方便,先註解這2行,避免反覆退出進入會話.

2.測試1:

--//選擇一個shared latch測試,我選擇"test shared non-parent l0" latch測試:

SYS@book> select * from shared_latches where name='test shared non-parent l0';

VERSION LATCH# NAME S

---------- ------ ------------------------- -

11.2.0.4.0 6 test shared non-parent l0 Y

2.測試一些細節不再列出,參考連結:http://blog.itpub.net/267265/viewspace-2641902/

--//測試XS模式的情況:

--//session 1:

SYS@book> @ shared_latch.txt "test shared non-parent l0" 1 1 2 x 100000

--//session 2:

SYS@book> @ spid

SID SERIAL# PROCESS SERVER SPID PID P_SERIAL# C50

---------- ---------- ------------------------ --------- ------ ------- ---------- --------------------------------------------------

1 11 31454 DEDICATED 31455 24 5 alter system kill session '1,11' immediate;

--//記下spid=31455.

SYS@book> @shared_latch.txt "test shared non-parent l0" 1 3 4 s 1

--//注意session 申請S mode.

--//window 3:執行:

$ rlwrap gdb -p 31455 -x spin_s.gdb

Breakpoint 1 at 0x93f97a8

Breakpoint 2 at 0x93f9b74

Breakpoint 3 at 0x9808932

Breakpoint 4 at 0x9809840

Breakpoint 5 at 0x37990d6400

Breakpoint 6 at 0x93f9ddc

Breakpoint 7 at 0x93faa36

Breakpoint 8 at 0xa865ca

Breakpoint 9 at 0xa874fa

Breakpoint 10 at 0xa875be

(gdb) c

Continuing.

...

kslgetl 6010d860, 1, 2126093176, 3991

ksl_get_shared_latch laddr:85f7f4c8, willing:1, where:-2043602896, why:96, mode:16

ksl_get_shared_latch laddr:85f7f4c8, willing:1, where:-2043602896, why:95, mode:8

ksl_get_shared_latch laddr:85f7f4c8, willing:1, where:-2043602896, why:96, mode:16

ksl_get_shared_latch laddr:85f7f4c8, willing:1, where:-2043602896, why:95, mode:8

ksl_get_shared_latch laddr:85f7f4c8, willing:1, where:-2043602896, why:96, mode:16

ksl_get_shared_latch laddr:85f7f4c8, willing:1, where:-2043602896, why:95, mode:8

ksl_get_shared_latch laddr:85f7f4c8, willing:1, where:-2043602896, why:96, mode:16

ksl_get_shared_latch laddr:60009a18, willing:1, where:3, why:4, mode:8

kslgess 60009a18, 8, 0, 3

kslskgs 60009a18, 0, 1129096976, 1129097520

---Type <return> to continue, or q <return> to quit---

skgpwwait 1129096760, 202182304, -2044672536, 0

sskgpwwait 1129096760, 202182304, -2044672536, 0

semop 315588608, 1129096560, 1, -1

--//按ctrl+c出現如下:

kslskgs 60009a18, 0, 1129096976, 1129097520

--//可以看出X模式的情況,申請S mode,第2程式直接呼叫semop.根本不做spin操作.

3.測試2:

--//測試SX模式的情況:

--//session 1:

SYS@book> @ shared_latch.txt "test shared non-parent l0" 1 1 2 s 100000

--//session 持有S mode.

--//session 2:

SYS@book> @shared_latch.txt "test shared non-parent l0" 1 3 4 x 1

--//注意session 申請x mode.

--//window 3:執行:

$ rlwrap gdb -p 31455 -x spin_s.gdb

..

ksl_get_shared_latch laddr:85f7f4c8, willing:1, where:-2043602896, why:95, mode:8

ksl_get_shared_latch laddr:85f7f4c8, willing:1, where:-2043602896, why:96, mode:16

ksl_get_shared_latch laddr:60009a18, willing:1, where:3, why:4, mode:16

kslgess 60009a18, 16, 0, 3

kslskgs 60009a18, 0, 1129096976, 1129097520

spin count loop: 2000 a875be

spin count loop: 1999 a875be

spin count loop: 1998 a875be

spin count loop: 1997 a875be

...

spin count loop: 3 a875be

spin count loop: 2 a875be

spin count loop: 1 a875be

kslskgs 60009a18, 0, 1129096976, 1129097520

spin count loop: 1 a875be

skgpwwait 1129096760, 202182304, -2044672536, 0

sskgpwwait 1129096760, 202182304, -2044672536, 0

semop 315588608, 1129096560, 1, -1

--//按ctrl+c後.

kslskgs 60009a18, 0, 1129096976, 1129097520

spin count loop: 2000 a875be

--//可以S模式的情況,申請X mode,第2程式spin_count=2000.

4.測試3:

--//Blocking mode,首先我對這個模式的理解不是非常清晰.

--//我的理解

A.當前X mode持有,不管S,X模式申請都會阻塞,再有程式申請的情況.

B.當前S mode持有,X模式申請,後續再有程式申請的情況.

--//也就是這個情況至少3個會話,我分別測試看看

--//session 1:

SYS@book> @ shared_latch.txt "test shared non-parent l0" 1 1 2 s 100000

--//session 2:

SYS@book> @ shared_latch.txt "test shared non-parent l0" 1 3 4 x 1

--//session 3:

--//spid=31572

SYS@book> @ shared_latch.txt "test shared non-parent l0" 1 5 6 s 1

--//gdb監測session 3程式:

$ rlwrap gdb -p 31572 -x spin_s.gdb

...

ksl_get_shared_latch laddr:85f7fa68, willing:1, where:-2042914736, why:95, mode:8

ksl_get_shared_latch laddr:85f7fa68, willing:1, where:-2042914736, why:96, mode:16

ksl_get_shared_latch laddr:60009a18, willing:1, where:5, why:6, mode:8

kslgess 60009a18, 8, 0, 5

kslskgs 60009a18, 0, -1923148048, -1923147504

skgpwwait -1923148264, 202182304, -2044655416, 0

sskgpwwait -1923148264, 202182304, -2044655416, 0

semop 315588608, -1923148464, 1, -1

kslskgs 60009a18, 0, -1923148048, -1923147504

--//申請S mode,沒有spin.

--//session 1:

SYS@book> @ shared_latch.txt "test shared non-parent l0" 1 1 2 s 100000

--//session 2:

SYS@book> @ shared_latch.txt "test shared non-parent l0" 1 3 4 x 1

--//session 3:

--//spid=31572

SYS@book> @ shared_latch.txt "test shared non-parent l0" 1 5 6 x 1

--//gdb監測session 3程式:

$ rlwrap gdb -p 31572 -x spin_s.gdb

...

ksl_get_shared_latch laddr:85f7fa68, willing:1, where:-2042914736, why:96, mode:16

ksl_get_shared_latch laddr:60009a18, willing:1, where:5, why:6, mode:16

kslgess 60009a18, 16, 0, 5

kslskgs 60009a18, 0, -1923148048, -1923147504

spin count loop: 2000 a875be

spin count loop: 1999 a875be

spin count loop: 1998 a875be

spin count loop: 1997 a875be

...

spin count loop: 1 a875be

kslskgs 60009a18, 0, -1923148048, -1923147504

spin count loop: 1 a875be

skgpwwait -1923148264, 202182304, -2044655416, 0

sskgpwwait -1923148264, 202182304, -2044655416, 0

semop 315588608, -1923148464, 1, -1

kslskgs 60009a18, 0, -1923148048, -1923147504

spin count loop: 2000 a875be

--//申請X mode,spin_count=2000.

--//XSS的情況:

ksl_get_shared_latch laddr:85f7fa68, willing:1, where:-2042914736, why:96, mode:16

ksl_get_shared_latch laddr:60009a18, willing:1, where:5, why:6, mode:8

kslgess 60009a18, 8, 0, 5

kslskgs 60009a18, 0, -1923148048, -1923147504

skgpwwait -1923148264, 202182304, -2044655416, 0

sskgpwwait -1923148264, 202182304, -2044655416, 0

semop 315588608, -1923148464, 1, -1

kslskgs 60009a18, 0, -1923148048, -1923147504

--//XSX的情況:

ksl_get_shared_latch laddr:85f7fa68, willing:1, where:-2042914736, why:96, mode:16

ksl_get_shared_latch laddr:60009a18, willing:1, where:5, why:6, mode:16

kslgess 60009a18, 16, 0, 5

kslskgs 60009a18, 0, -1923148048, -1923147504

spin count loop: 2000 a875be

spin count loop: 1999 a875be

spin count loop: 1998 a875be

spin count loop: 1997 a875be

spin count loop: 1996 a875be

spin count loop: 1995 a875be

...

sskgpwwait -1923148264, 202182304, -2044655416, 0

semop 315588608, -1923148464, 1, -1

kslskgs 60009a18, 0, -1923148048, -1923147504

spin count loop: 2000 a875be

--//總之:阻塞申請X mode,spin_count=2000.S mode 直接呼叫semop休眠.

5.總結

--//畫一個表格:

S mode get X mode get

Held in S mode Compatible _spin_count

Held in X mode 0 _spin_count

Blocking mode 0 _spin_count

[20190419]shared latch spin count 2.txt

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