Linux Kernel  3.7.1
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ioprio.h
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1 #ifndef IOPRIO_H
2 #define IOPRIO_H
3 
4 #include <linux/sched.h>
5 #include <linux/iocontext.h>
6 
7 /*
8  * Gives us 8 prio classes with 13-bits of data for each class
9  */
10 #define IOPRIO_BITS (16)
11 #define IOPRIO_CLASS_SHIFT (13)
12 #define IOPRIO_PRIO_MASK ((1UL << IOPRIO_CLASS_SHIFT) - 1)
13 
14 #define IOPRIO_PRIO_CLASS(mask) ((mask) >> IOPRIO_CLASS_SHIFT)
15 #define IOPRIO_PRIO_DATA(mask) ((mask) & IOPRIO_PRIO_MASK)
16 #define IOPRIO_PRIO_VALUE(class, data) (((class) << IOPRIO_CLASS_SHIFT) | data)
17 
18 #define ioprio_valid(mask) (IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
19 
20 /*
21  * These are the io priority groups as implemented by CFQ. RT is the realtime
22  * class, it always gets premium service. BE is the best-effort scheduling
23  * class, the default for any process. IDLE is the idle scheduling class, it
24  * is only served when no one else is using the disk.
25  */
26 enum {
31 };
32 
33 /*
34  * 8 best effort priority levels are supported
35  */
36 #define IOPRIO_BE_NR (8)
37 
38 enum {
42 };
43 
44 /*
45  * Fallback BE priority
46  */
47 #define IOPRIO_NORM (4)
48 
49 /*
50  * if process has set io priority explicitly, use that. if not, convert
51  * the cpu scheduler nice value to an io priority
52  */
53 static inline int task_nice_ioprio(struct task_struct *task)
54 {
55  return (task_nice(task) + 20) / 5;
56 }
57 
58 /*
59  * This is for the case where the task hasn't asked for a specific IO class.
60  * Check for idle and rt task process, and return appropriate IO class.
61  */
62 static inline int task_nice_ioclass(struct task_struct *task)
63 {
64  if (task->policy == SCHED_IDLE)
65  return IOPRIO_CLASS_IDLE;
66  else if (task->policy == SCHED_FIFO || task->policy == SCHED_RR)
67  return IOPRIO_CLASS_RT;
68  else
69  return IOPRIO_CLASS_BE;
70 }
71 
72 /*
73  * For inheritance, return the highest of the two given priorities
74  */
75 extern int ioprio_best(unsigned short aprio, unsigned short bprio);
76 
77 extern int set_task_ioprio(struct task_struct *task, int ioprio);
78 
79 #endif