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;spin count loop: 1 a875be
skgpwwait -331400584, 202182304, 0, 70000
kslskgs 60009a18, 0, -331400368, -331399824
spin count loop: 2000 a875be
spin count loop: 1999 a875be
spin count loop: 1998 a875be
...
spin count loop: 1 a875be
skgpwwait -331400584, 202182304, 0, 50000
kslskgs 60009a18, 0, -331400368, -331399824
spin count loop: 2000 a875be
spin count loop: 1999 a875be
...
spin count loop: 2 a875be
spin count loop: 1 a875be
skgpwwait -331400584, 202182304, 0, 50000
kslskgs 60009a18, 0, -331400368, -331399824
spin count loop: 2000 a875be
spin count loop: 1999 a875be
...
spin count loop: 1963 a875be
spin count loop: 1962 a875be
spin count loop: 1961 a875be
---Type <return> to continue, or q <return> to quit---q
Quit
--//注意看skgpwwait最后参数,实际上就是sleep的时间,单位微秒.spin count不是10,而是2000.
(gdb) info br 10
Num Type Disp Enb Address What
10 breakpoint keep y 0x0000000000a875be <kslskgs+200>
breakpoint already hit 18041 times
silent
printf " spin count loop: %d %x\n", $r13,$rip
c
--//使用跟踪可以发现如下:
$ strace -fttT -p 31247
Process 31247 attached - interrupt to quit
11:06:41.497253 select(0, [], [], [], {0, 40191}) = 0 (Timeout) <0.040333>
11:06:41.537915 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050145>
11:06:41.588209 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050140>
11:06:41.638518 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050108>
11:06:41.688774 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050146>
11:06:41.739070 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050147>
11:06:41.789366 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050110>
11:06:41.839640 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050141>
11:06:41.889947 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050143>
11:06:41.940240 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050121>
11:06:41.990509 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050153>
11:06:42.040831 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050145>
11:06:42.091124 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050151>
11:06:42.141462 select(0, [], [], [], {0, 50000}) = 0 (Timeout) <0.050161>
...
总结:
1.不要在生产系统做这样测试.
2.shared latch 持有X 模式,申请 X 模式阻塞,spin_count=_spin_count.与exclusive latch不同.
3.对于修改latch类的参数仅仅sleepN参数有效.
4.其它模式比如SX,XS.另外写一篇blog测试.我看了连接,我还忘记考虑Blocking mode下的情况.
--//链接:http://andreynikolaev.wordpress.com/2011/01/14/spin-tales-part-2-shared-latches-in-oracle-9-2-11g/
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
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