include/linux/ioprio.h

   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_CLASS_SHIFT      (13)
  11 #define IOPRIO_PRIO_MASK        ((1UL << IOPRIO_CLASS_SHIFT) - 1)
  12
  13 #define IOPRIO_PRIO_CLASS(mask) ((mask) >> IOPRIO_CLASS_SHIFT)
  14 #define IOPRIO_PRIO_DATA(mask)  ((mask) & IOPRIO_PRIO_MASK)
  15 #define IOPRIO_PRIO_VALUE(class, data)  (((class) << IOPRIO_CLASS_SHIFT) | data)
  16
  17 #define ioprio_valid(mask)      (IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
  18
  19 /*
  20  * These are the io priority groups as implemented by CFQ. RT is the realtime
  21  * class, it always gets premium service. BE is the best-effort scheduling
  22  * class, the default for any process. IDLE is the idle scheduling class, it
  23  * is only served when no one else is using the disk.
  24  */
  25 enum {
  26         IOPRIO_CLASS_NONE,
  27         IOPRIO_CLASS_RT,
  28         IOPRIO_CLASS_BE,
  29         IOPRIO_CLASS_IDLE,
  30 };
  31
  32 /*
  33  * 8 best effort priority levels are supported
  34  */
  35 #define IOPRIO_BE_NR    (8)
  36
  37 enum {
  38         IOPRIO_WHO_PROCESS = 1,
  39         IOPRIO_WHO_PGRP,
  40         IOPRIO_WHO_USER,
  41 };
  42
  43 /*
  44  * Fallback BE priority
  45  */
  46 #define IOPRIO_NORM     (4)
  47
  48 /*
  49  * if process has set io priority explicitly, use that. if not, convert
  50  * the cpu scheduler nice value to an io priority
  51  */
  52 static inline int task_nice_ioprio(struct task_struct *task)
  53 {
  54         return (task_nice(task) + 20) / 5;
  55 }
  56
  57 /*
  58  * This is for the case where the task hasn't asked for a specific IO class.
  59  * Check for idle and rt task process, and return appropriate IO class.
  60  */
  61 static inline int task_nice_ioclass(struct task_struct *task)
  62 {
  63         if (task->policy == SCHED_IDLE)
  64                 return IOPRIO_CLASS_IDLE;
  65         else if (task->policy == SCHED_FIFO || task->policy == SCHED_RR)
  66                 return IOPRIO_CLASS_RT;
  67         else
  68                 return IOPRIO_CLASS_BE;
  69 }
  70
  71 /*
  72  * For inheritance, return the highest of the two given priorities
  73  */
  74 extern int ioprio_best(unsigned short aprio, unsigned short bprio);
  75
  76 extern int set_task_ioprio(struct task_struct *task, int ioprio);
  77
  78 #endif