以下这段伪代码来自于OraPub的Craig A. Shallahamer，这段代码并不长但基本对获取latch、spin、sleep的行为都描述清楚了，如果你对latch仍不甚了了，那么这段代码会对你很有帮助: 
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Function Get_Latch(latch_name,mode){ If Mode eq ‘immediate’ {
If Fast_Get(latch_name) {
return TRUE
Else {
return FALSE
}
}
Else {
If Fast_Get(latch_name)
Then {
v$latch.gets++
return TRUE
}
Else {
v$latch.misses++
for try = 0 .. large_number
{
if Spin_Get(latch_name)
Then {
return TRUE
}
Else {
T0 = time
Sleep(try)
T1=time
Register_Event("latch free",T1-T0)
}
} -- spin/sleep loop
}
}
}Function Fast_Get(latch_name){ If try_to_get_latch(latch_name)
Then {
return TRUE
}
Else {
return FALSE
}
}Function Spin_Get(latch_name){ v$latch.spin_get++
for i = 1 to _spin_count
{
If Fast_Get(latch_name)
Then {
return TRUE
}
}
}Function Sleep(try)
{ v$latch.sleeps++
v$latch.sleep[try]++
sleeptime =
decode(try,0,0,1,10,2,20,3,~40,4,~80,...~2000)
sleep(sleeptime)
} |
本文转自maclean_007 51CTO博客，原文链接:http://blog.51cto.com/maclean/1277799