Originální popis anglicky:
sched_setaffinity, sched_getaffinity - set and get a process's CPU affinity mask
Návod, kniha: Linux Programmer's Manual
#include <sched.h>
int sched_setaffinity(pid_t pid, unsigned int
len, unsigned long *mask);
int sched_getaffinity(pid_t pid, unsigned int
len, unsigned long *mask);
sched_setaffinity sets the CPU affinity mask of the process denoted by
pid. If
pid is zero, then the current process is used.
The affinity mask is represented by the bitmask stored in
mask. The least
significant bit corresponds to the first logical processor number on the
system, while the most significant bit corresponds to the last logical
processor number on the system. A set bit corresponds to a legally schedulable
CPU while an unset bit corresponds to an illegally schedulable CPU. In other
words, a process is bound to and will only run on processors whose
corresponding bit is set. Usually, all bits in the mask are set.
The argument
len is the length (in bytes) of the data pointed to by
mask. Normally this is the size of a word on the system. For
compatibility with future versions of the Linux kernel, since this size can
change, the bitmask supplied must be at least as large as the affinity mask
stored in the kernel.
The function
sched_getaffinity writes into the pointer supplied by
mask that has size
len the affinity mask of process
pid.
If
pid is zero, then the mask of the current process is returned.
On success,
sched_setaffinity returns 0. On error, -1 is returned, and
errno is set appropriately.
On success,
sched_getaffinity always returns the size (in bytes) of the
affinity mask used by the kernel. On error, -1 is returned, and
errno
is set appropriately.
- EFAULT
- A supplied memory address was invalid.
- EINVAL
- The affinity bitmask mask contains no processors
that are physically on the system, or the length len is smaller
than the size of the affinity mask used by the kernel.
- EPERM
- The calling process does not have appropriate privileges.
The process calling sched_setaffinity needs an effective user ID
equal to the user ID or effective user ID of the process identified by
pid, or it must possess the CAP_SYS_NICE capability.
- ESRCH
- The process whose ID is pid could not be found.
The affinity syscalls were introduced in Linux kernel 2.5.8. The library calls
were introduced in glibc 2.3, and are still in glibc 2.3.2. Later glibc 2.3.2
development versions changed this interface to one without the
len
field, and still later versions reverted again. The glibc prototype is now
/* Set the CPU affinity for a task */
extern int sched_setaffinity (pid_t pid, size_t cpusetsize,
const cpu_set_t *cpuset);
/* Get the CPU affinity for a task */
extern int sched_getaffinity (pid_t pid, size_t cpusetsize,
cpu_set_t *cpuset);
getpriority(2),
nice(2),
sched_get_priority_max(2),
sched_get_priority_min(2),
sched_getscheduler(2),
sched_setscheduler(2),
setpriority(2),
capabilities(7)
sched_setscheduler(2) has a description of the Linux scheduling
scheme.
