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_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 */
  26enum {
  27        IOPRIO_CLASS_NONE,
  28        IOPRIO_CLASS_RT,
  29        IOPRIO_CLASS_BE,
  30        IOPRIO_CLASS_IDLE,
  31};
  32
  33/*
  34 * 8 best effort priority levels are supported
  35 */
  36#define IOPRIO_BE_NR    (8)
  37
  38enum {
  39        IOPRIO_WHO_PROCESS = 1,
  40        IOPRIO_WHO_PGRP,
  41        IOPRIO_WHO_USER,
  42};
  43
  44/*
  45 * if process has set io priority explicitly, use that. if not, convert
  46 * the cpu scheduler nice value to an io priority
  47 */
  48#define IOPRIO_NORM     (4)
  49static inline int task_ioprio(struct io_context *ioc)
  50{
  51        if (ioprio_valid(ioc->ioprio))
  52                return IOPRIO_PRIO_DATA(ioc->ioprio);
  53
  54        return IOPRIO_NORM;
  55}
  56
  57static inline int task_ioprio_class(struct io_context *ioc)
  58{
  59        if (ioprio_valid(ioc->ioprio))
  60                return IOPRIO_PRIO_CLASS(ioc->ioprio);
  61
  62        return IOPRIO_CLASS_BE;
  63}
  64
  65static inline int task_nice_ioprio(struct task_struct *task)
  66{
  67        return (task_nice(task) + 20) / 5;
  68}
  69
  70/*
  71 * This is for the case where the task hasn't asked for a specific IO class.
  72 * Check for idle and rt task process, and return appropriate IO class.
  73 */
  74static inline int task_nice_ioclass(struct task_struct *task)
  75{
  76        if (task->policy == SCHED_IDLE)
  77                return IOPRIO_CLASS_IDLE;
  78        else if (task->policy == SCHED_FIFO || task->policy == SCHED_RR)
  79                return IOPRIO_CLASS_RT;
  80        else
  81                return IOPRIO_CLASS_BE;
  82}
  83
  84/*
  85 * For inheritance, return the highest of the two given priorities
  86 */
  87extern int ioprio_best(unsigned short aprio, unsigned short bprio);
  88
  89extern int set_task_ioprio(struct task_struct *task, int ioprio);
  90
  91#endif
  92