tools

Official reference

See below for a sample ionice tool. Usage::

# ionice -c<class> -n<level> -p<pid>

If pid isn’t given, the current process is assumed. IO priority settings are inherited on fork, so you can use ionice to start the process at a given level::

# ionice -c2 -n0 /bin/ls

will run ls at the best-effort scheduling class at the highest priority. For a running process, you can give the pid instead::

# ionice -c1 -n2 -p100

will change pid 100 to run at the realtime scheduling class, at priority 2.

ionice.c tool::

#include #include #include #include #include #include <sys/ptrace.h> #include <asm/unistd.h>

extern int sys_ioprio_set(int, int, int); extern int sys_ioprio_get(int, int);

#if defined(i386) #define NR_ioprio_set 289 #define __NR_ioprio_get 290 #elif defined(__ppc) #define NR_ioprio_set 273 #define __NR_ioprio_get 274 #elif defined(__x86_64) #define __NR_ioprio_set 251 #define __NR_ioprio_get 252 #else #error “Unsupported arch” #endif

static inline int ioprio_set(int which, int who, int ioprio) { return syscall(__NR_ioprio_set, which, who, ioprio); }

static inline int ioprio_get(int which, int who) { return syscall(__NR_ioprio_get, which, who); }

enum { IOPRIO_CLASS_NONE, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE, };

enum { IOPRIO_WHO_PROCESS = 1, IOPRIO_WHO_PGRP, IOPRIO_WHO_USER, };

#define IOPRIO_CLASS_SHIFT 13

const char *to_prio[] = { “none”, “realtime”, “best-effort”, “idle”, };

int main(int argc, char *argv[]) { int ioprio = 4, set = 0, ioprio_class = IOPRIO_CLASS_BE; int c, pid = 0;

while ((c = getopt(argc, argv, "+n:c:p:")) != EOF) {
	switch (c) {
	case 'n':
		ioprio = strtol(optarg, NULL, 10);
		set = 1;
		break;
	case 'c':
		ioprio_class = strtol(optarg, NULL, 10);
		set = 1;
		break;
	case 'p':
		pid = strtol(optarg, NULL, 10);
		break;
	}
}

switch (ioprio_class) {
	case IOPRIO_CLASS_NONE:
		ioprio_class = IOPRIO_CLASS_BE;
		break;
	case IOPRIO_CLASS_RT:
	case IOPRIO_CLASS_BE:
		break;
	case IOPRIO_CLASS_IDLE:
		ioprio = 7;
		break;
	default:
		printf("bad prio class `%d`\n", ioprio_class);
		return 1;
}

if (!set) {
	if (!pid && argv[optind])
		pid = strtol(argv[optind], NULL, 10);

	ioprio = ioprio_get(IOPRIO_WHO_PROCESS, pid);

	printf("pid=`%d`, `%d`\n", pid, ioprio);

	if (ioprio == -1)
		perror("ioprio_get");
	else {
		ioprio_class = ioprio >> IOPRIO_CLASS_SHIFT;
		ioprio = ioprio & 0xff;
		printf("`%s`: prio `%d`\n", to_prio[ioprio_class], ioprio);
	}
} else {
	if (ioprio_set(IOPRIO_WHO_PROCESS, pid, ioprio | ioprio_class << IOPRIO_CLASS_SHIFT) == -1) {
		perror("ioprio_set");
		return 1;
	}

	if (argv[optind])
		execvp(argv[optind], &argv[optind]);
}

return 0;   }

March 11 2005, Jens Axboe jens.axboe@oracle.com