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CFS调度器之虚拟时钟...

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gatieme
2016-06-29 14:39:26 +08:00
parent 2c8ecd99bb
commit 9f850015c2
1 changed files with 2 additions and 3 deletions
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study/kernel/01-process/05-schedule/04-cfs/02-vruntime/README.md
+2 -3
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@@ -121,7 +121,7 @@ static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
忽略舍入和溢出检查, calc_delta_fair函数所做的就是根据下列公式计算:
$$ delta =delta \times \dfrac{NICE_0_LOAD}{curr->se->load.weight} ;(if curr.nice!=NICE_0_LOAD)$$
$$ delta =delta \times \dfrac{NICE\_0\_LOAD}{curr->se->load.weight}$$
@@ -134,10 +134,9 @@ $$ delta =delta \times \dfrac{NICE_0_LOAD}{curr->se->load.weight} ;(if curr.ni
| 条件 | 公式 |
|:-------:|:-------:|
| curr.nice != NICE_0_LOAD | $curr->vruntime += delta\\_exec \times \dfrac{NICE\\_0\\_LOAD}{curr->se->load.weight}$|
| curr.nice != NICE_0_LOAD | $curr->vruntime += delta\\_exec \times \dfrac{NICE\\_0\\_LOAD}{curr->se->load.weight}$ |
| curr.nice == NICE_0_LOAD | $ curr->vruntime += delta $ |
在该计算中可以派上用场了, 回想一下子,　可知越重要的进程会有越高的优先级(即, 越低的nice值), 会得到更大的权重, 因此累加的虚拟运行时间会小一点,
根据公式可知, nice = 0的进程(优先级120), 则虚拟时间和物理时间是相等的, 即current->se->load.weight等于NICE_0_LAD的情况.