1/* ionice.c - set or get process I/O scheduling class and priority
2 *
3 * Copyright 2015 Rob Landley <rob@landley.net>
4 *
5 * It would be really nice if there was a standard, but no. There is
6 * Documentation/block/ioprio.txt in the linux source.
7
8USE_IONICE(NEWTOY(ionice, "^tc#<0>3=2n#<0>7=5p#", TOYFLAG_USR|TOYFLAG_BIN))
9USE_IORENICE(NEWTOY(iorenice, "?<1>3", TOYFLAG_USR|TOYFLAG_BIN))
10
11config IONICE
12  bool "ionice"
13  default y
14  help
15    usage: ionice [-t] [-c CLASS] [-n LEVEL] [COMMAND...|-p PID]
16
17    Change the I/O scheduling priority of a process. With no arguments
18    (or just -p), display process' existing I/O class/priority.
19
20    -c	CLASS = 1-3: 1(realtime), 2(best-effort, default), 3(when-idle)
21    -n	LEVEL = 0-7: (0 is highest priority, default = 5)
22    -p	Affect existing PID instead of spawning new child
23    -t	Ignore failure to set I/O priority
24
25    System default iopriority is generally -c 2 -n 4.
26
27config IORENICE
28  bool "iorenice"
29  default y
30  help
31    usage: iorenice PID [CLASS] [PRIORITY]
32
33    Display or change I/O priority of existing process. CLASS can be
34    "rt" for realtime, "be" for best effort, "idle" for only when idle, or
35    "none" to leave it alone. PRIORITY can be 0-7 (0 is highest, default 4).
36*/
37
38#define FOR_ionice
39#include "toys.h"
40#include <sys/syscall.h>
41
42GLOBALS(
43  long pid;
44  long level;
45  long class;
46)
47
48static int ioprio_get(void)
49{
50  return syscall(__NR_ioprio_get, 1, (int)TT.pid);
51}
52
53static int ioprio_set(void)
54{
55  int prio = ((int)TT.class << 13) | (int)TT.level;
56
57  return syscall(__NR_ioprio_set, 1, (int)TT.pid, prio);
58}
59
60void ionice_main(void)
61{
62  if (!TT.pid && !toys.optc) error_exit("Need -p or COMMAND");
63  if (toys.optflags == FLAG_p) {
64    int p = ioprio_get();
65    xprintf("%s: prio %d\n",
66      (char *[]){"unknown", "Realtime", "Best-effort", "Idle"}[(p>>13)&3],
67      p&7);
68  } else {
69    if (-1 == ioprio_set() && !(toys.optflags&FLAG_t)) perror_exit("set");
70    if (!TT.pid) xexec(toys.optargs);
71  }
72}
73
74void iorenice_main(void)
75{
76  char *classes[] = {"none", "rt", "be", "idle"};
77
78  TT.pid = atolx(*toys.optargs);
79  if (toys.optc == 1) {
80    int p = ioprio_get();
81
82    if (p == -1) perror_exit("read priority");
83    TT.class = (p>>13)&3;
84    p &= 7;
85    xprintf("Pid %ld, class %s (%ld), prio %d\n",
86            TT.pid, classes[TT.class], TT.class, p);
87    return;
88  }
89
90  for (TT.class = 0; TT.class<4; TT.class++)
91    if (!strcmp(toys.optargs[toys.optc-1], classes[TT.class])) break;
92  if (toys.optc == 3 || TT.class == 4) TT.level = atolx(toys.optargs[1]);
93  else TT.level = 4;
94  TT.class &= 3;
95
96  if (-1 == ioprio_set()) perror_exit("set");
97}
98