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 
8 USE_IONICE(NEWTOY(ionice, "^tc#<0>3=2n#<0>7=5p#", TOYFLAG_USR|TOYFLAG_BIN))
9 USE_IORENICE(NEWTOY(iorenice, "?<1>3", TOYFLAG_USR|TOYFLAG_BIN))
10 
11 config 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 
27 config 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 
42 GLOBALS(
43   long pid;
44   long level;
45   long class;
46 )
47 
48 static int ioprio_get(void)
49 {
50   return syscall(__NR_ioprio_get, 1, (int)TT.pid);
51 }
52 
53 static 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 
60 void 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 
74 void 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