1 /* vi: set sw=4 ts=4: */
3 * taskset - retrieve or set a processes' CPU affinity
4 * Copyright (c) 2006 Bernhard Reutner-Fischer
6 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
8 //config:config TASKSET
9 //config: bool "taskset (4.1 kb)"
12 //config: Retrieve or set a processes's CPU affinity.
13 //config: This requires sched_{g,s}etaffinity support in your libc.
15 //config:config FEATURE_TASKSET_FANCY
16 //config: bool "Fancy output"
18 //config: depends on TASKSET
20 //config: Needed for machines with more than 32-64 CPUs:
21 //config: affinity parameter 0xHHHHHHHHHHHHHHHHHHHH can be arbitrarily long
22 //config: in this case. Otherwise, it is limited to sizeof(long).
24 //applet:IF_TASKSET(APPLET_NOEXEC(taskset, taskset, BB_DIR_USR_BIN, BB_SUID_DROP, taskset))
26 //kbuild:lib-$(CONFIG_TASKSET) += taskset.o
28 //usage:#define taskset_trivial_usage
29 //usage: "[-p] [HEXMASK] PID | PROG ARGS"
30 //usage:#define taskset_full_usage "\n\n"
31 //usage: "Set or get CPU affinity\n"
32 //usage: "\n -p Operate on an existing PID"
34 //usage:#define taskset_example_usage
35 //usage: "$ taskset 0x7 ./dgemm_test&\n"
36 //usage: "$ taskset -p 0x1 $!\n"
37 //usage: "pid 4790's current affinity mask: 7\n"
38 //usage: "pid 4790's new affinity mask: 1\n"
39 //usage: "$ taskset 0x7 /bin/sh -c './taskset -p 0x1 $$'\n"
40 //usage: "pid 6671's current affinity mask: 1\n"
41 //usage: "pid 6671's new affinity mask: 1\n"
42 //usage: "$ taskset -p 1\n"
43 //usage: "pid 1's current affinity mask: 3\n"
45 * Not yet implemented:
46 * -a/--all-tasks (affect all threads)
47 * needs to get TIDs from /proc/PID/task/ and use _them_ as "pid" in sched_setaffinity(pid)
48 * -c/--cpu-list (specify CPUs via "1,3,5-7")
54 typedef unsigned long ul;
55 #define SZOF_UL (unsigned)(sizeof(ul))
56 #define BITS_UL (unsigned)(sizeof(ul)*8)
57 #define MASK_UL (unsigned)(sizeof(ul)*8 - 1)
59 #if ENABLE_FEATURE_TASKSET_FANCY
60 #define TASKSET_PRINTF_MASK "%s"
61 /* craft a string from the mask */
62 static char *from_mask(const ul *mask, unsigned sz_in_bytes)
64 char *str = xzalloc((sz_in_bytes+1) * 2); /* we will leak it */
69 p += sprintf(p, "%08lx", v);
71 p += sprintf(p, "%016lx", v);
73 p += sprintf(p, "%032lx", v); /* :) */
74 sz_in_bytes -= SZOF_UL;
75 if ((int)sz_in_bytes <= 0)
78 while (str[0] == '0' && str[1])
83 #define TASKSET_PRINTF_MASK "%lx"
84 static unsigned long long from_mask(ul *mask, unsigned sz_in_bytes UNUSED_PARAM)
90 static unsigned long *get_aff(int pid, unsigned *sz)
93 unsigned long *mask = NULL;
94 unsigned sz_in_bytes = *sz;
97 mask = xrealloc(mask, sz_in_bytes);
98 r = sched_getaffinity(pid, sz_in_bytes, (void*)mask);
102 if (errno == EINVAL && (int)sz_in_bytes > 0)
104 bb_perror_msg_and_die("can't %cet pid %d's affinity", 'g', pid);
106 //bb_error_msg("get mask[0]:%lx sz_in_bytes:%d", mask[0], sz_in_bytes);
111 int taskset_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
112 int taskset_main(int argc UNUSED_PARAM, char **argv)
115 unsigned mask_size_in_bytes;
118 const char *current_new;
121 /* NB: we mimic util-linux's taskset: -p does not take
122 * an argument, i.e., "-pN" is NOT valid, only "-p N"!
123 * Indeed, util-linux-2.13-pre7 uses:
124 * getopt_long(argc, argv, "+pchV", ...), not "...p:..." */
126 opt_p = getopt32(argv, "^+" "p" "\0" "-1" /* at least 1 arg */);
132 if (*argv) { /* "-p <aff> <pid> ...rest.is.ignored..." */
133 pid_str = *argv; /* NB: *argv != NULL in this case */
135 /* else it was just "-p <pid>", and *argv == NULL */
136 pid = xatoul_range(pid_str, 1, ((unsigned)(pid_t)ULONG_MAX) >> 1);
143 mask_size_in_bytes = SZOF_UL;
144 current_new = "current";
146 mask = get_aff(pid, &mask_size_in_bytes);
148 printf("pid %d's %s affinity mask: "TASKSET_PRINTF_MASK"\n",
149 pid, current_new, from_mask(mask, mask_size_in_bytes));
151 /* Either it was just "-p <pid>",
152 * or it was "-p <aff> <pid>" and we came here
153 * for the second time (see goto below) */
159 memset(mask, 0, mask_size_in_bytes);
161 /* Affinity was specified, translate it into mask */
162 /* it is always in hex, skip "0x" if it exists */
163 if (aff[0] == '0' && (aff[1]|0x20) == 'x')
166 if (!ENABLE_FEATURE_TASKSET_FANCY) {
167 mask[0] = xstrtoul(aff, 16);
172 i = 0; /* bit pos in mask[] */
174 /* aff is ASCII hex string, accept very long masks in this form.
175 * Process hex string AABBCCDD... to ulong mask[]
176 * from the rightmost nibble, which is least-significant.
177 * Bits not fitting into mask[] are ignored: (example: 1234
178 * in 12340000000000000000000000000000000000000ff)
180 last_char = strchrnul(aff, '\0');
181 while (last_char > aff) {
189 else if ((c|0x20) >= 'a' && (c|0x20) <= 'f')
190 val = (c|0x20) - ('a' - 10);
192 bb_error_msg_and_die("bad affinity '%s'", aff);
194 if (i < mask_size_in_bytes * 8) {
195 mask[i / BITS_UL] |= val << (i & MASK_UL);
196 //bb_error_msg("bit %d set", i);
199 * We can error out here, but we don't.
200 * For one, kernel itself ignores bits in mask[]
201 * which do not map to any CPUs:
202 * if mask[] has one 32-bit long element,
203 * but you have only 8 CPUs, all bits beyond first 8
204 * are ignored, silently.
205 * No point in making bits past 31th to be errors.
211 /* Set pid's or our own (pid==0) affinity */
212 if (sched_setaffinity(pid, mask_size_in_bytes, (void*)mask))
213 bb_perror_msg_and_die("can't %cet pid %d's affinity", 's', pid);
214 //bb_error_msg("set mask[0]:%lx", mask[0]);
216 if (!argv[0]) /* "-p <aff> <pid> [...ignored...]" */
217 goto print_aff; /* print new affinity and exit */
219 BB_EXECVP_or_die(argv);