LXR linux/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 */
  25enum {
  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
  37enum {
  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 */
  52static 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 */
  61static 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 */
  74extern int ioprio_best(unsigned short aprio, unsigned short bprio);
  75
  76extern int set_task_ioprio(struct task_struct *task, int ioprio);
  77
  78#endif
  79