[20190423]那个更快的疑问3.txt

痛定思痛。 2022-01-05 22:04 242阅读 0赞

\[20190423\]那个更快的疑问3.txt  
  
\--//前一阵子,做了11g在单表单条记录唯一索引扫描的测试,摘要如下:  
\--//参考链接:  
http://blog.itpub.net/267265/viewspace-2636321/  
http://blog.itpub.net/267265/viewspace-2636342/  
  
\--//在链接中我解析唯一索引查询的情况，为什么10g快于11g，链接：http://blog.itpub.net/267265/viewspace-2639920/  
\--//差异在于10g很少做times的系统调用上.10g下仅仅116次.而11g高达200179.(getrusage与times调用次数比大约是7:2)  
\--//我当时的感觉10g漏写times系统函数调用，导致这样的情况，11g把它补上了。  
\--//实际上有网友提出疑问.我的测试下的结论有问题.当时测试的情况如下:  
\--//11g的测试:  
$ strace -f -c sqlplus -s -l scott/book @m1.txt 1e5 id=1\_unique\_index 0 >/dev/null  
...  
% time     seconds  usecs/call     calls    errors syscall  
\------ ----------- ----------- --------- --------- ----------------  
 72.78    0.043919           0    700708           getrusage  
 19.80    0.011947           0    200179           times  
  6.67    0.004024         671         6         3 wait4  
  0.24    0.000147          29         5           clone  
  0.18    0.000106           0       375         2 read  
  0.16    0.000096           0       264       106 open  
...  
\------ ----------- ----------- --------- --------- ----------------  
100.00    0.060341                902967       206 total  
  
\--//1e5次执行times调用消耗0.011947秒,放大10倍(我每个session执行次数是1e6)也就是0.119470秒,什么可能产生这么大的差异.  
\--//仔细查看,我觉得strace跟踪记录的syscallsyscall.linux标准C函数.看不出oracle内部函数调用次数.  
\--//我当时的解析是这增加的times调用一定是11g版本唯一索引扫描中增加几个oracle内部函数调用,导致11g的唯一索引  
\--//扫描更慢,如何验证我当时确实不知道? 最近shared latch测试,建立一些gdb脚本,有了这些脚本可以latch获得释放的情况.  
  
1.环境:  
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  
  
2.建立测试脚本:  
  
create table t as select rownum id from dual ;  
create unique index pk\_t on t(id);  
alter table t modify id  not null ;  
create table job\_times (sid number, time\_ela number,method varchar2(20));  
\--//分析表略.  
  
$ cat z1.txt  
set verify off  
host sleep $(echo &&3/50 | bc -l )  
variable vmethod varchar2(20);  
exec :vmethod := '&&2';  
insert into job\_times values ( sys\_context ('userenv', 'sid') ,dbms\_utility.get\_time ,:vmethod) ;  
commit ;  
declare  
v\_id number;  
v\_d date;  
begin  
    for i in 1 .. &&1 loop  
        select /\*+  &&3 \*/ count (\*) into v\_id from t where id=1 ;  
    end loop;  
end ;  
/  
update job\_times set time\_ela = dbms\_utility.get\_time - time\_ela where sid=sys\_context ('userenv', 'sid') and method=:vmethod;  
commit;  
quit  
  
3.分别测试:  
$ sqlplus -s -l scott/book @z1.txt 1e6 id=unindex 0 >/dev/null  
  
SCOTT@book> Select method,count(\*),round(avg(TIME\_ELA),0),sum(TIME\_ELA) from job\_times group by method order by 3 ;  
METHOD                 COUNT(\*) ROUND(AVG(TIME\_ELA),0) SUM(TIME\_ELA)  
\-------------------- ---------- ---------------------- -------------  
id=unindex                    1                   2723          2723  
  
\--//在10g下重复测试:  
SCOTT@test> @ &r/ver1  
PORT\_STRING                    VERSION        BANNER  
\------------------------------ -------------- ----------------------------------------------------------------  
x86\_64/Linux 2.4.xx            10.2.0.4.0     Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bi  
  
SCOTT@test> select method,count(\*),round(avg(TIME\_ELA),0),sum(TIME\_ELA) from job\_times group by method order by 3 ;  
METHOD                 COUNT(\*) ROUND(AVG(TIME\_ELA),0) SUM(TIME\_ELA)  
\-------------------- ---------- ---------------------- -------------  
id=unindex                    1                   1591          1591  
\--//即使单用户执行10g下比11g快许多.  
  
3.通过gdb脚本分析:  
\--//11g:  
SCOTT@book> @ spid  
       SID    SERIAL\# PROCESS                  SERVER    SPID       PID  P\_SERIAL\# C50  
\---------- ---------- ------------------------ --------- ------ ------- ---------- --------------------------------------------------  
        88         89 65066                    DEDICATED 65067       30         65 alter system kill session '88,89' immediate;  
  
\--//执行多次3次以上避免递归.  
select count(\*) from t where id=1;  
\--//打开window 2:  
$ gdb -p 65067 -x latch11g.gdb  
(gdb) c  
Continuing.  
ksl\_get\_shared\_latch laddr:85f7fe28, willing:1, where:-2050764096, why:95, mode:8  
ksl\_get\_shared\_latch laddr:85f7fe28, willing:1, where:-2050764096, why:96, mode:16  
ksl\_get\_shared\_latch laddr:85f7fe28, willing:1, where:-2050764096, why:95, mode:8  
kslgetl 844ed538, 0, 49, 2062  
kslgetl 8353a258, 1, 16777771, 2053  
ksl\_get\_shared\_latch laddr:85f7fe28, willing:1, where:-2050764096, why:96, mode:16  
ksl\_get\_shared\_latch laddr:85f7fe28, willing:1, where:-2050764096, why:95, mode:8  
ksl\_get\_shared\_latch laddr:85f7fe28, willing:1, where:-2050764096, why:96, mode:16  
  
\--//看到ksl\_get\_shared\_latch 6次,kslgetl 2次,看看是什么latch.  
> select addr,name,level\#,latch\#,gets,misses,sleeps,immediate\_gets,immediate\_misses,waiters\_woken,waits\_holding\_latch,spin\_gets,wait\_time from v$latch\_children where addr=lpad(upper('85f7fe28'),'16','0')  
ADDR             NAME             LEVEL\#     LATCH\#       GETS     MISSES     SLEEPS IMMEDIATE\_GETS IMMEDIATE\_MISSES WAITERS\_WOKEN WAITS\_HOLDING\_LATCH  SPIN\_GETS  WAIT\_TIME  
\---------------- ---------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------  
0000000085F7FE28 session idle bit      1         14       1095          0          0              0                0             0                   0          0          0  
  
\--//session idle bit 第一次看见,我看了我的测试机器,一共24次children latch.估计跟CPU数量有关.我在另外的会话重复测试  
\--//ksl\_get\_shared\_latch的地址不一样,而kslgetl 也是2次都是一样.  
  
> select addr,name,level\#,latch\#,gets,misses,sleeps,immediate\_gets,immediate\_misses,waiters\_woken,waits\_holding\_latch,spin\_gets,wait\_time from v$latch\_children where addr=lpad(upper('844ed538'),'16','0')  
ADDR             NAME                LEVEL\#     LATCH\#       GETS     MISSES     SLEEPS IMMEDIATE\_GETS IMMEDIATE\_MISSES WAITERS\_WOKEN WAITS\_HOLDING\_LATCH  SPIN\_GETS  WAIT\_TIME  
\---------------- ------------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------  
00000000844ED538 simulator lru latch      6        185        560          1          0       72795239          3207148             0                   0          1          0  
  
> select addr,name,level\#,latch\#,gets,misses,sleeps,immediate\_gets,immediate\_misses,waiters\_woken,waits\_holding\_latch,spin\_gets,wait\_time from v$latch\_children where addr=lpad(upper('8353a258'),'16','0')  
ADDR             NAME                 LEVEL\#     LATCH\#       GETS     MISSES     SLEEPS IMMEDIATE\_GETS IMMEDIATE\_MISSES WAITERS\_WOKEN WAITS\_HOLDING\_LATCH  SPIN\_GETS  WAIT\_TIME  
\---------------- -------------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------  
000000008353A258 simulator hash latch      7        186   72792634          0          0              0                0             0                   0          0          0  
  
\--//奇怪这两个latch我从来没有过,而且奇怪的是根本看不到cbc latch.  
\--//在10g下重复测试看看(注10g shared latch 的函数是kslgetsl )  
  
Breakpoint 1 at 0x7a0644  
Breakpoint 2 at 0x7a0a44  
Breakpoint 3 at 0x3bccd52  
Breakpoint 4 at 0x3be9a04  
Breakpoint 5 at 0x3181cd6400  
Breakpoint 6 at 0x78ef44  
Function "ksl\_get\_shared\_latch" not defined.  
Make breakpoint pending on future shared library load? (y or \[n\]) \[answered N; input not from terminal\]  
Breakpoint 7 at 0x78f4bc  
Breakpoint 8 at 0x79054c  
\--//奇怪10g没有ksl\_get\_shared\_latchoracle内部函数.注解这部分内容.  
  
(gdb) c  
Continuing.  
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:80, mode:8  
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:81, mode:16  
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:80, mode:8  
kslgetl 7a10aaa0, 1, 0, 2741  
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:81, mode:16  
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:80, mode:8  
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:81, mode:16  
\--//看到kslgetsl 6次,kslgetl 1次,看看是什么latch.  
SYS@test> select addr,name,level\#,latch\#,gets,misses,sleeps,immediate\_gets,immediate\_misses,waiters\_woken,waits\_holding\_latch,spin\_gets,wait\_time from v$latch\_children where addr=lpad(upper('7cfb24f8'),'16','0');  
ADDR             NAME                 LEVEL\#     LATCH\#       GETS     MISSES     SLEEPS IMMEDIATE\_GETS IMMEDIATE\_MISSES WAITERS\_WOKEN WAITS\_HOLDING\_LATCH  SPIN\_GETS  WAIT\_TIME  
\---------------- -------------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------  
000000007CFB24F8 session idle bit          1          7       7112          0          0              0                0             0                   0          0          0  
  
SYS@test> select addr,name,level\#,latch\#,gets,misses,sleeps,immediate\_gets,immediate\_misses,waiters\_woken,waits\_holding\_latch,spin\_gets,wait\_time from v$latch\_children where addr=lpad(upper('7a10aaa0'),'16','0');  
ADDR             NAME                   LEVEL\#     LATCH\#       GETS     MISSES     SLEEPS IMMEDIATE\_GETS IMMEDIATE\_MISSES WAITERS\_WOKEN WAITS\_HOLDING\_LATCH  SPIN\_GETS  WAIT\_TIME  
\---------------- ---------------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------  
000000007A10AAA0 shared pool simulator       8        241     146325          1          0              0                0             0                   0          1          0  
  
\--//你可以再次执行sql语句看看gets的变化:  
SYS@test> select addr,name,level\#,latch\#,gets,misses,sleeps,immediate\_gets,immediate\_misses,waiters\_woken,waits\_holding\_latch,spin\_gets,wait\_time from v$latch\_children where addr=lpad(upper('7cfb24f8'),'16','0');  
ADDR             NAME             LEVEL\#     LATCH\#       GETS     MISSES     SLEEPS IMMEDIATE\_GETS IMMEDIATE\_MISSES WAITERS\_WOKEN WAITS\_HOLDING\_LATCH  SPIN\_GETS  WAIT\_TIME  
\---------------- ---------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------  
000000007CFB24F8 session idle bit      1          7       7118          0          0              0                0             0                   0          0          0  
  
SYS@test> select addr,name,level\#,latch\#,gets,misses,sleeps,immediate\_gets,immediate\_misses,waiters\_woken,waits\_holding\_latch,spin\_gets,wait\_time from v$latch\_children where addr=lpad(upper('7a10aaa0'),'16','0');  
ADDR             NAME                  LEVEL\#     LATCH\#       GETS     MISSES     SLEEPS IMMEDIATE\_GETS IMMEDIATE\_MISSES WAITERS\_WOKEN WAITS\_HOLDING\_LATCH  SPIN\_GETS  WAIT\_TIME  
\---------------- --------------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------  
000000007A10AAA0 shared pool simulator      8        241     146326          1          0              0                0             0                   0          1          0  
  
\--//说明跟踪到的get变化没有问题.我在11g看了latch的变化,只不过simulator lru latch 变成了IMMEDIATE\_GETS数量增加:  
> select addr,name,level\#,latch\#,gets,misses,sleeps,immediate\_gets,immediate\_misses,waiters\_woken,waits\_holding\_latch,spin\_gets,wait\_time from v$latch\_children where addr=lpad(upper('8353a258'),'16','0')  
ADDR             NAME                                         LEVEL\#     LATCH\#       GETS     MISSES     SLEEPS IMMEDIATE\_GETS IMMEDIATE\_MISSES WAITERS\_WOKEN WAITS\_HOLDING\_LATCH  SPIN\_GETS  WAIT\_TIME  
\---------------- ---------------------------------------- ---------- ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------  
000000008353A258 simulator hash latch                              7        186   72792639          0          0              0                0             0                   0          0          0  
  
> select addr,name,level\#,latch\#,gets,misses,sleeps,immediate\_gets,immediate\_misses,waiters\_woken,waits\_holding\_latch,spin\_gets,wait\_time from v$latch\_children where addr=lpad(upper('844ed538'),'16','0')  
ADDR             NAME                                         LEVEL\#     LATCH\#       GETS     MISSES     SLEEPS IMMEDIATE\_GETS IMMEDIATE\_MISSES WAITERS\_WOKEN WAITS\_HOLDING\_LATCH  SPIN\_GETS  WAIT\_TIME  
\---------------- ---------------------------------------- ---------- ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------  
00000000844ED538 simulator lru latch                               6        185        563          1          0       72795248          3207148             0                   0          1          0  
  
\--//执行sql语句再查看.  
> select addr,name,level\#,latch\#,gets,misses,sleeps,immediate\_gets,immediate\_misses,waiters\_woken,waits\_holding\_latch,spin\_gets,wait\_time from v$latch\_children where addr=lpad(upper('8353a258'),'16','0')  
ADDR             NAME                                         LEVEL\#     LATCH\#       GETS     MISSES     SLEEPS IMMEDIATE\_GETS IMMEDIATE\_MISSES WAITERS\_WOKEN WAITS\_HOLDING\_LATCH  SPIN\_GETS  WAIT\_TIME  
\---------------- ---------------------------------------- ---------- ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------  
000000008353A258 simulator hash latch                              7        186   72792640          0          0              0                0             0                   0          0          0  
  
> select addr,name,level\#,latch\#,gets,misses,sleeps,immediate\_gets,immediate\_misses,waiters\_woken,waits\_holding\_latch,spin\_gets,wait\_time from v$latch\_children where addr=lpad(upper('844ed538'),'16','0')  
ADDR             NAME                                         LEVEL\#     LATCH\#       GETS     MISSES     SLEEPS IMMEDIATE\_GETS IMMEDIATE\_MISSES WAITERS\_WOKEN WAITS\_HOLDING\_LATCH  SPIN\_GETS  WAIT\_TIME  
\---------------- ---------------------------------------- ---------- ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------  
00000000844ED538 simulator lru latch                               6        185        563          1          0       72795249          3207148             0                   0          1          0  
  
\--//我估计跟一些参数有关:  
kslgetl 844ed538, 0, 49, 2062  
kslgetl 8353a258, 1, 16777771, 2053  
\--//我猜测0表示no willing等待. 1表示willing等待.  
\--//我最后猜测也许正是11g下代码改动使用ksl\_get\_shared\_latch,多了1次kslgetl调用,使用导致11g下每次执行多了2次times syscall,  
\--//可以讲11g下唯一索引扫描是一个退步.  
\--//至于为什么没有阻塞看不到cbc latch获取和释放,我给再探究看看...  
  
4.我加入1个字段看看:  
drop table t purge ;  
create table t as select rownum id,'test' name  from dual ;  
create unique index pk\_t on t(id);  
alter table t modify id  not null ;  
  
$ cat z1.txt  
set verify off  
host sleep $(echo &&3/50 | bc -l )  
variable vmethod varchar2(20);  
exec :vmethod := '&&2';  
insert into job\_times values ( sys\_context ('userenv', 'sid') ,dbms\_utility.get\_time ,:vmethod) ;  
commit ;  
declare  
v\_id number;  
v\_d date;  
v\_name varchar2(4) ;  
begin  
    for i in 1 .. &&1 loop  
        select /\*+  &&3 \*/ name  into v\_name from t where id=1 ;  
    end loop;  
end ;  
/  
update job\_times set time\_ela = dbms\_utility.get\_time - time\_ela where sid=sys\_context ('userenv', 'sid') and method=:vmethod;  
commit;  
quit  
  
\--//重复测试:  
\--//11g:  
SCOTT@book> Select method,count(\*),round(avg(TIME\_ELA),0),sum(TIME\_ELA) from job\_times group by method order by 3 ;  
METHOD                 COUNT(\*) ROUND(AVG(TIME\_ELA),0) SUM(TIME\_ELA)  
\-------------------- ---------- ---------------------- -------------  
id=unindex\_name               1                   2135          2135  
id=unindex                    1                   2723          2723  
  
\--//10g:  
SCOTT@test> select method,count(\*),round(avg(TIME\_ELA),0),sum(TIME\_ELA) from job\_times group by method order by 3 ;  
METHOD                 COUNT(\*) ROUND(AVG(TIME\_ELA),0) SUM(TIME\_ELA)  
\-------------------- ---------- ---------------------- -------------  
id=unindex\_name               1                   1359          1359  
id=unindex                    1                   1591          1591  
  
\--//真心搞不懂,回表反而更快一些.oracle许多东西真心搞不懂....  
\--//感觉如果访问数据块缓存数据块,没有阻塞无需要获取cbc latch吗?  
  
5.附上gdb脚本:  
\--//11g版本:  
$ cat latch11g.gdb  
break kslgetl  
  commands  
    silent  
    printf "kslgetl %x, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
break kslges  
  commands  
    silent  
    printf "kslges %x, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
break skgpwwait  
  commands  
    silent  
    printf "skgpwwait %d, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
break sskgpwwait  
  commands  
    silent  
    printf "sskgpwwait %d, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
break semop  
  commands  
    silent  
    printf "semop %d, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
\#break \*0x93f9ddc  
\#  commands  
\#    silent  
\#    printf " spin count loop: %d %d %x\\n", $rax,$rcx,$rip  
\#    c  
\#  end  
  
\#\#  
break kslgetsl\_w  
  commands  
    silent  
    printf "kslgetsl\_w laddr:%x, willing:%d, where:%d, why:%d, mode:%d\\n", $rdi, $rsi, $rdx, $rcx, $r8  
    c  
  end  
  
break ksl\_get\_shared\_latch  
  commands  
    silent  
    printf "ksl\_get\_shared\_latch laddr:%x, willing:%d, where:%d, why:%d, mode:%d\\n", $rdi, $rsi, $rdx, $rcx, $r8  
    c  
  end  
  
break kslgess  
  commands  
    silent  
    printf "kslgess %x, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
break kslskgs  
  commands  
    silent  
    printf "kslskgs %x, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
break kslfre  
  commands  
    silent  
    printf "kslfre %x, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
\#break \*0xa875be  
\#  commands  
\#    silent  
\#    printf " spin count loop: %d %x\\n", $r13,$rip  
\#    c  
\#  end  
  
\--//10g版本:  
$ cat latch10g.gdb  
break kslgetl  
  commands  
    silent  
    printf "kslgetl %x, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
break kslges  
  commands  
    silent  
    printf "kslges %x, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
break skgpwwait  
  commands  
    silent  
    printf "skgpwwait %d, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
break sskgpwwait  
  commands  
    silent  
    printf "sskgpwwait %d, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
break semop  
  commands  
    silent  
    printf "semop %d, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
\#break \*0x93f9ddc  
\#  commands  
\#    silent  
\#    printf " spin count loop: %d %d %x\\n", $rax,$rcx,$rip  
\#    c  
\#  end  
  
\#\#  
break kslgetsl  
  commands  
    silent  
    printf "kslgetsl laddr:%x, willing:%d, where:%d, why:%d, mode:%d\\n", $rdi, $rsi, $rdx, $rcx, $r8  
    c  
  end  
  
\#break ksl\_get\_shared\_latch  
\#  commands  
\#    silent  
\#    printf "ksl\_get\_shared\_latch laddr:%x, willing:%d, where:%d, why:%d, mode:%d\\n", $rdi, $rsi, $rdx, $rcx, $r8  
\#    c  
\#  end  
  
break kslgess  
  commands  
    silent  
    printf "kslgess %x, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
break kslskgs  
  commands  
    silent  
    printf "kslskgs %x, %d, %d, %d\\n", $rdi, $rsi, $rdx, $rcx  
    c  
  end  
  
\#break \*0xa875be  
\#  commands  
\#    silent  
\#    printf " spin count loop: %d %x\\n", $r13,$rip  
\#    c  
\#  end

转载于:https://www.cnblogs.com/lfree/p/10755324.html

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