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进程调度之优先级详解...

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gatieme
2016-06-19 21:00:20 +08:00
parent 6a56482ff9
commit fcf515c571
2 changed files with 71 additions and 2 deletions
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study/kernel/01-process/05-schedule/04-priority/README.md
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@@ -175,7 +175,10 @@ linux把进程区分为实时进程和非实时进程, 其中非实时进程进
````
| 宏 | 值 | 描述 |
| ------------- |:-------------:|
| ------------- |:-------------:|:-------------:|
| MIN_NICE | -20 | 对应于优先级100, 可以使用NICE_TO_PRIO和PRIO_TO_NICE转换 |
| MAX_NICE | 19 | 对应于优先级139, 可以使用NICE_TO_PRIO和PRIO_TO_NICE转换 |
| NICE_WIDTH | 40 | nice值得范围宽度, 即[-20, 19]共40个数字的宽度 |
| MAX_RT_PRIO, MAX_USER_RT_PRIO | 100 | 实时进程的最大优先级 |
| MAX_PRIO | 140 | 普通进程的最大优先级 |
| DEFAULT_PRIO | 120 | 进程的默认优先级, 对应于nice=0 |
study/kernel/01-process/05-schedule/05-nice/README.md
+67 -1
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@@ -78,7 +78,10 @@ linux优先级操作的系统调用有nice和getpriority, setpriority
````
| 宏 | 值 | 描述 |
| ------------- |:-------------:|
| ------------- |:-------------:|:-------------:|
| MIN_NICE | -20 | 对应于优先级100, 可以使用NICE_TO_PRIO和PRIO_TO_NICE转换 |
| MAX_NICE | 19 | 对应于优先级139, 可以使用NICE_TO_PRIO和PRIO_TO_NICE转换 |
| NICE_WIDTH | 40 | nice值得范围宽度, 即[-20, 19]共40个数字的宽度 |
| MAX_RT_PRIO, MAX_USER_RT_PRIO | 100 | 实时进程的最大优先级 |
| MAX_PRIO | 140 | 普通进程的最大优先级 |
| DEFAULT_PRIO | 120 | 进程的默认优先级, 对应于nice=0 |
@@ -307,13 +310,76 @@ clamp宏定义在[include/linux/kernel.h, L757](http://lxr.free-electrons.com/so
* 如果val大于hi, 即val > hi > lo, 则返回hi
##task_nice
-------
[task_nice](http://lxr.free-electrons.com/source/include/linux/sched.h?=4.6#L2409)定义在[include/linux/sched.h, L2409](http://lxr.free-electrons.com/source/include/linux/sched.h?=4.6#L2409), 如下所示
其实就是将进程的静态优先级static_prio通过PRIO_TO_NICE转换成nice值
```c
/**
* task_nice - return the nice value of a given task.
* @p: the task in question.
*
* Return: The nice value [ -20 ... 0 ... 19 ].
*/
static inline int task_nice(const struct task_struct *p)
{
return PRIO_TO_NICE((p)->static_prio);
}
```
##clamp_val
-------
clamp_val宏定义在[include/linux/kernel.h, L757](http://lxr.free-electrons.com/source/include/linux/kernel.h?v=4.6#L768), 其定义如下
```c
/*
* ..and if you can't take the strict
* types, you can specify one yourself.
*
* Or not use min/max/clamp at all, of course.
*/
#define min_t(type, x, y) ({ \
type __min1 = (x); \
type __min2 = (y); \
__min1 < __min2 ? __min1: __min2; })
#define max_t(type, x, y) ({ \
type __max1 = (x); \
type __max2 = (y); \
__max1 > __max2 ? __max1: __max2; })
/**
* clamp_t - return a value clamped to a given range using a given type
* @type: the type of variable to use
* @val: current value
* @lo: minimum allowable value
* @hi: maximum allowable value
*
* This macro does no typechecking and uses temporary variables of type
* 'type' to make all the comparisons.
*/
#define clamp_t(type, val, lo, hi) min_t(type, max_t(type, val, lo), hi)
/**
* clamp_val - return a value clamped to a given range using val's type
* @val: current value
* @lo: minimum allowable value
* @hi: maximum allowable value
*
* This macro does no typechecking and uses temporary variables of whatever
* type the input argument 'val' is. This is useful when val is an unsigned
* type and min and max are literals that will otherwise be assigned a signed
* integer type.
*/
#define clamp_val(val, lo, hi) clamp_t(typeof(val), val, lo, hi)
```
##can_nice
-------