toys/taskset.c

/* vi: set sw=4 ts=4:
 *
 * taskset.c - Retrieve or set the CPU affinity of a process.
 *
 * Copyright 2012 Elie De Brauwer <eliedebrauwer@gmail.com>
 *
 * Not in SUSv4.

USE_TASKSET(NEWTOY(taskset, "<1>2a", TOYFLAG_BIN|TOYFLAG_NEEDROOT))

config TASKSET
	bool "taskset"
	default y
	help
	  usage: taskset [-a] [mask] PID

	  When mask is present the CPU affinity mask of a given PID will
	  be set to this mask. When a mask is not given, the mask will
	  be printed. A mask is a hexadecimal string where the bit position
	..matches the cpu number.
	  -a	Set/get the affinity of all tasks of a PID.
*/

#define _GNU_SOURCE
#include "toys.h"

static int str_to_cpu_set(char * mask, cpu_set_t *set)
{
	int size = strlen(mask);
	char *ptr = mask + size - 1;
	int cpu = 0;

	CPU_ZERO(set);
	if (size > 1 && mask[0] == '0' && mask[1] == 'x')
		mask += 2;

	while(ptr >= mask)
	{
		char val = 0;
		if ( *ptr >= '0' && *ptr <= '9')
			val = *ptr - '0';
		else if (*ptr >= 'a' && *ptr <= 'f')
			val = 10 + (*ptr - 'a');
		else
			return -1;

		if (val & 1) CPU_SET(cpu,  set);
		if (val & 2) CPU_SET(cpu + 1, set);
		if (val & 4) CPU_SET(cpu + 2, set);
		if (val & 8) CPU_SET(cpu + 3, set);

		ptr--;
		cpu += 4;
	}
	return 0;
}

static char * cpu_set_to_str(cpu_set_t *set)
{
	int cpu;
	char * ptr = toybuf;
	for (cpu=(8*sizeof(cpu_set_t) - 4); cpu >= 0; cpu -= 4)
	{
		char val = 0;
		if (CPU_ISSET(cpu, set))	 val |= 1;
		if (CPU_ISSET(cpu + 1, set)) val |= 2;
		if (CPU_ISSET(cpu + 2, set)) val |= 4;
		if (CPU_ISSET(cpu + 3, set)) val |= 8;
		if (ptr != toybuf || val != 0)
		{
			if (val < 10)
				*ptr = '0' + val;
			else
				*ptr = 'a' + (val - 10);
			ptr++;
		}
	}
	*ptr = 0;
	return toybuf;
}

static void do_taskset(pid_t pid)
{
	cpu_set_t mask;
	if (sched_getaffinity(pid, sizeof(mask), &mask))
		perror_exit("failed to get %d's affinity", pid);

	printf("pid %d's current affinity mask: %s\n", pid, cpu_set_to_str(&mask));

	if (toys.optc == 2)
	{
		if (str_to_cpu_set(toys.optargs[0], &mask))
			perror_exit("failed to parse CPU mask: %s", toys.optargs[0]);

		if (sched_setaffinity(pid, sizeof(mask), &mask))
			perror_exit("failed to set %d's affinity", pid);

		if (sched_getaffinity(pid, sizeof(mask), &mask))
			perror_exit("failed to get %d's affinity", pid);

		printf("pid %d's new affinity mask: %s\n", pid, cpu_set_to_str(&mask));
	}
}

static int task_cb(struct dirtree *new)
{
	if (S_ISDIR(new->st.st_mode))
	{
		if (strstr(new->name,"/task/\0") != NULL)
			return DIRTREE_RECURSE;

		pid_t tid = atoi(new->name);
		if (tid)
			do_taskset(tid);
	}
	return 0;
}

void taskset_main(void)
{
	char * pidstr = (toys.optc==1)?toys.optargs[0]:toys.optargs[1];

	if ( toys.optflags & 0x1 )
	{
		sprintf(toybuf, "/proc/%s/task/", pidstr);
		dirtree_read(toybuf, task_cb);
	}
	else
	{
		pid_t tid = atoi(pidstr);
		if (tid)
			do_taskset(tid);
	}
}