[20190402]Library Cache mutex.txt

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

$ cat m2.txt

set verify off

column a noprint new_value v_a;

--select mod ( &&3 ,3) a from dual ;

--alter session set optimizer_index_cost_adj= &&3;

host sleep $(echo &&3/50| bc -l )

insert into job_times values ( sys_context ('userenv', 'sid') ,dbms_utility.get_time ,'&&2') ;

commit ;

declare

v_id number;

v_d date;

begin

for i in 1 .. &&1 loop

--select 1 into v_id from dual ;

--select sysdate into v_d from dual ;

select deptno into v_id from dept where deptno=10;

end loop;

end ;

/

update job_times set time_ela = dbms_utility.get_time - time_ela where sid=sys_context ('userenv', 'sid') and method='&&2';

commit;

--quit

--//執行許多次,就可以在 x$mutex_sleep_history有記錄,出現MUTEX_TYPE='Library Cache'的情況

$ seq 150 | xargs -I {} -P 150 bash -c "sqlplus -s -l scott/book @m2.txt 1e6 f2_150 {} >/dev/null"

SYS@book> @ mutexy 16 a31kd5tkdvvmm

HASH SUM_SLEEPS SUM_GETS LOCATION MUTEX_TYPE MUTEX_ADDR SQLID KGLNAOWN C100

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

1692266099 161187946 600188278 kksfbc [KKSCHLPIN1] Cursor Pin 000000007C88E330 a31kd5tkdvvmm SELECT DEPTNO FROM DEPT WHERE DEPTNO=10

1692266099 9215322 1.8927E+11 kksLockDelete [KKSCHLPIN6] Cursor Pin 000000007C88E330 a31kd5tkdvvmm SELECT DEPTNO FROM DEPT WHERE DEPTNO=10

1692266099 5019588 1.0546E+11 kksfbc [KKSCHLFSP2] Cursor Pin 000000007C88E330 a31kd5tkdvvmm SELECT DEPTNO FROM DEPT WHERE DEPTNO=10

1692266099 1351526 63672414 kgllkc1 57 Library Cache 000000007C957128 a31kd5tkdvvmm SELECT DEPTNO FROM DEPT WHERE DEPTNO=10

1692266099 499588 9089718 kkslce [KKSCHLPIN2] Cursor Pin 000000007C957128 a31kd5tkdvvmm SELECT DEPTNO FROM DEPT WHERE DEPTNO=10

1692266099 212212 3838112 kglGetHandleReference 124 Library Cache 000000007C957128 a31kd5tkdvvmm SELECT DEPTNO FROM DEPT WHERE DEPTNO=10

1692266099 131248 1919076 kgllkdl1 85 Library Cache 000000007C957128 a31kd5tkdvvmm SELECT DEPTNO FROM DEPT WHERE DEPTNO=10

1692266099 10118 1814754 kglhdgn2 106 Library Cache 000000007C957128 a31kd5tkdvvmm SELECT DEPTNO FROM DEPT WHERE DEPTNO=10

8 rows selected.

--//探究MUTEX_TYPE='Library Cache',MUTEX_ADDR='000000007C957128'在哪裡,還有1個LOCATION問題?

--//我執行許多次才出現這樣的情況.

2.分析:

SYS@book> @ fcha 000000007C957128

Find in which heap (UGA, PGA or Shared Pool) the memory address 000000007C957128 resides...

WARNING!!! This script will query X$KSMSP, which will cause heavy shared pool latch contention

in systems under load and with large shared pool. This may even completely hang

your instance until the query has finished! You probably do not want to run this in production!

Press ENTER to continue, CTRL+C to cancel...

LOC KSMCHPTR KSMCHIDX KSMCHDUR KSMCHCOM KSMCHSIZ KSMCHCLS KSMCHTYP KSMCHPAR

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

SGA 000000007C956FB8 1 1 KGLHD 560 recr 80 00

--//執行如下,也可以獲得類似結果:

SELECT * FROM x$ksmsp WHERE TO_NUMBER ('000000007C957128', 'xxxxxxxxxxxxxxxx') between TO_NUMBER(KSMCHPTR, 'xxxxxxxxxxxxxxxx') and TO_NUMBER(KSMCHPTR, 'xxxxxxxxxxxxxxxx')+KSMCHSIZ -1;

ADDR INDX INST_ID KSMCHIDX KSMCHDUR KSMCHCOM KSMCHPTR KSMCHSIZ KSMCHCLS KSMCHTYP KSMCHPAR

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

00007F3CEDE1A5B8 16459 1 1 1 KGLHD 000000007C956FB8 560 recr 80 00

SYS@book> @ sharepool/shp4 a31kd5tkdvvmm 0

TEXT KGLHDADR KGLHDPAR C40 KGLHDLMD KGLHDPMD KGLHDIVC KGLOBHD0 KGLOBHD6 KGLOBHS0 KGLOBHS6 KGLOBT16 N0_6_16 N20 KGLNAHSH KGLOBT03 KGLOBT09

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

子游標控制程式碼地址 000000007C7F8B90 000000007C956FE8 SELECT DEPTNO FROM DEPT WHERE DEPTNO=10 0 0 0 000000007C4468D8 000000007C88E3D8 4528 8088 3072 15688 15688 1692266099 a31kd5tkdvvmm 0

父遊標控制程式碼地址 000000007C956FE8 000000007C956FE8 SELECT DEPTNO FROM DEPT WHERE DEPTNO=10 0 0 0 000000007CA7BFE8 00 4720 0 0 4720 4720 1692266099 a31kd5tkdvvmm 65535

--//可以發現MUTEX_ADDR='000000007C957128'的地址與父遊標控制程式碼的地址比較接近.實際上從KSMCHCOM=KGLHD也可以確定,

SYS@book> @ fcha 000000007C956FE8

Find in which heap (UGA, PGA or Shared Pool) the memory address 000000007C956FE8 resides...

WARNING!!! This script will query X$KSMSP, which will cause heavy shared pool latch contention

in systems under load and with large shared pool. This may even completely hang

your instance until the query has finished! You probably do not want to run this in production!

Press ENTER to continue, CTRL+C to cancel...

LOC KSMCHPTR KSMCHIDX KSMCHDUR KSMCHCOM KSMCHSIZ KSMCHCLS KSMCHTYP KSMCHPAR

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

SGA 000000007C956FB8 1 1 KGLHD 560 recr 80 00

SELECT * FROM x$ksmsp WHERE TO_NUMBER ('000000007C956FE8', 'xxxxxxxxxxxxxxxx') between TO_NUMBER(KSMCHPTR, 'xxxxxxxxxxxxxxxx') and TO_NUMBER(KSMCHPTR, 'xxxxxxxxxxxxxxxx')+KSMCHSIZ-1;

ADDR INDX INST_ID KSMCHIDX KSMCHDUR KSMCHCOM KSMCHPTR KSMCHSIZ KSMCHCLS KSMCHTYP KSMCHPAR

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

00007F3CEDDFBC00 12611 1 1 1 KGLHD 000000007C956FB8 560 recr 80 00

--//library cache mutex結構體在父遊標控制程式碼地址裡面.

--//0x7C957128=2090168616 0x7C956FB8=2090168248 2090168616-2090168248 = 368,在父遊標控制程式碼地址偏移368位元組處.

3.知道地址就可以模擬問題產生:

--//session 1:

SCOTT@book> @ spid

SID SERIAL# PROCESS SERVER SPID PID P_SERIAL# C50

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

32 35 10708 DEDICATED 10709 26 84 alter system kill session '32,35' immediate;

--//32=0x20

--//session 2:

SYS@book> oradebug setmypid

Statement processed.

SYS@book> oradebug peek 0x000000007C957128 8

[07C957128, 07C957130) = 00000000 00000000

SYS@book> oradebug poke 0x000000007C957128 8 0x0000004400000020

BEFORE: [07C957128, 07C957130) = 00000000 00000000

AFTER: [07C957128, 07C957130) = 00000020 00000044

--//session 1:

SCOTT@book> @ m2.txt 1 c1 0

1 row created.

Commit complete.

--//掛起!!注第一次執行會掛起,第2次就不會了.

--//session 2:

SYS@book> @ wait

P1RAW P2RAW P3RAW P1 P2 P3 SID SERIAL# SEQ# EVENT STATUS STATE WAIT_TIME_MICRO SECONDS_IN_WAIT WAIT_CLASS

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

0000000064DDEE73 0000004400000020 0000000000000039 1692266099 2.9206E+11 57 32 33 38 library cache: mutex X ACTIVE WAITING 35878972 36 Concurrency

--//出現library cache: mutex X 等待.

SYS@book> oradebug poke 0x000000007C957128 8 0x0

BEFORE: [07C957128, 07C957130) = 00000020 00000044

AFTER: [07C957128, 07C957130) = 00000000 00000000

--//再次執行,因為該游標已經cache. PL/sql語句中的sql語句與sqlplus執行的sql語句方式不同.

SYS@book> select * from v$open_cursor where sql_id='a31kd5tkdvvmm';

SADDR SID USER_NAME ADDRESS HASH_VALUE SQL_ID SQL_TEXT LAST_SQL_ACTIVE_TIM SQL_EXEC_ID CURSOR_TYPE

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

000000008635DE10 32 SCOTT 000000007C956FE8 1692266099 a31kd5tkdvvmm SELECT DEPTNO FROM DEPT WHERE DEPTNO=10 PL/SQL CURSOR CACHED

--//第一次執行就cache了.第2次執行不會在library cache上出現阻塞.

SYS@book> oradebug poke 0x000000007C957128 8 0x0000004400000020

BEFORE: [07C957128, 07C957130) = 00000000 00000000

AFTER: [07C957128, 07C957130) = 00000020 00000044

SCOTT@book> @ m2.txt 1 c1 0

1 row created.

Commit complete.

PL/SQL procedure successfully completed.

11 rows updated.

Commit complete.

--//可以正常執行.但是退出會出現問題.

SCOTT@book> quit

--//掛起!!

SYS@book> @ wait

P1RAW P2RAW P3RAW P1 P2 P3 SID SERIAL# SEQ# EVENT STATUS STATE WAIT_TIME_MICRO SECONDS_IN_WAIT WAIT_CLASS

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

0000000064DDEE73 0000004400000020 0000000000000055 1692266099 2.9206E+11 85 32 35 57 library cache: mutex X ACTIVE WAITING 17103974 17 Concurrency

--//還有1個情況是阻塞無法查詢x$mutex_sleep_history檢視,

SYS@book> @ mutexy 6 a31kd5tkdvvmm

--//掛起!!取消後正常!!

SYS@book> oradebug poke 0x000000007C957128 8 0x00

BEFORE: [07C957128, 07C957130) = 00000020 00000044

AFTER: [07C957128, 07C957130) = 00000000 00000000

----