src/basic/ioprio.h

   1 #ifndef IOPRIO_H
   2 #define IOPRIO_H
   3
   4 /* This is minimal version of Linux' linux/ioprio.h header file, which
   5  * is licensed GPL2 */
   6
   7 #include <sys/syscall.h>
   8 #include <unistd.h>
   9
  10 /*
  11  * Gives us 8 prio classes with 13-bits of data for each class
  12  */
  13 #define IOPRIO_BITS             16
  14 #define IOPRIO_N_CLASSES        8
  15 #define IOPRIO_CLASS_SHIFT      13
  16 #define IOPRIO_PRIO_MASK        ((1UL << IOPRIO_CLASS_SHIFT) - 1)
  17
  18 #define IOPRIO_PRIO_CLASS(mask) ((mask) >> IOPRIO_CLASS_SHIFT)
  19 #define IOPRIO_PRIO_DATA(mask)  ((mask) & IOPRIO_PRIO_MASK)
  20 #define IOPRIO_PRIO_VALUE(class, data)  (((class) << IOPRIO_CLASS_SHIFT) | data)
  21
  22 #define ioprio_valid(mask)      (IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
  23
  24 /*
  25  * These are the io priority groups as implemented by CFQ. RT is the realtime
  26  * class, it always gets premium service. BE is the best-effort scheduling
  27  * class, the default for any process. IDLE is the idle scheduling class, it
  28  * is only served when no one else is using the disk.
  29  */
  30 enum {
  31         IOPRIO_CLASS_NONE,
  32         IOPRIO_CLASS_RT,
  33         IOPRIO_CLASS_BE,
  34         IOPRIO_CLASS_IDLE,
  35 };
  36
  37 /*
  38  * 8 best effort priority levels are supported
  39  */
  40 #define IOPRIO_BE_NR    (8)
  41
  42 enum {
  43         IOPRIO_WHO_PROCESS = 1,
  44         IOPRIO_WHO_PGRP,
  45         IOPRIO_WHO_USER,
  46 };
  47
  48 static inline int ioprio_set(int which, int who, int ioprio) {
  49         return syscall(__NR_ioprio_set, which, who, ioprio);
  50 }
  51
  52 static inline int ioprio_get(int which, int who) {
  53         return syscall(__NR_ioprio_get, which, who);
  54 }
  55
  56 #endif