1. 进程的亲和性
NAME
sched_setaffinity, sched_getaffinity - set and get a process's CPU affinity mask
SYNOPSIS
#define _GNU_SOURCE
#include <sched.h>
int sched_setaffinity(pid_t pid, size_t cpusetsize,
cpu_set_t *mask);
int sched_getaffinity(pid_t pid, size_t cpusetsize,
cpu_set_t *mask);
DESCRIPTION
A process's CPU affinity mask determines the set of CPUs on which it is eligible to run. On a multiprocessor system, setting the CPU affinity mask can be used to obtain performance benefits.
For example, by dedicating one CPU to a particular process (i.e., setting the affinity mask of that process to specify a single CPU, and setting the affinity mask of all other processes to
exclude that CPU), it is possible to ensure maximum execution speed for that process. Restricting a process to run on a single CPU also avoids the performance cost caused by the cache invalida-
tion that occurs when a process ceases to execute on one CPU and then recommences execution on a different CPU.
A CPU affinity mask is represented by the cpu_set_t structure, a "CPU set", pointed to by mask. A set of macros for manipulating CPU sets is described in CPU_SET(3).
sched_setaffinity() sets the CPU affinity mask of the process whose ID is pid to the value specified by mask. If pid is zero, then the calling process is used. The argument cpusetsize is the
length (in bytes) of the data pointed to by mask. Normally this argument would be specified as sizeof(cpu_set_t).
If the process specified by pid is not currently running on one of the CPUs specified in mask, then that process is migrated to one of the CPUs specified in mask.
sched_getaffinity() writes the affinity mask of the process whose ID is pid into the cpu_set_t structure pointed to by mask. The cpusetsize argument specifies the size (in bytes) of mask. If
pid is zero, then the mask of the calling process is returned.
RETURN VALUE
On success, sched_setaffinity() and sched_getaffinity() return 0. On error, -1 is returned, and errno is set appropriately.
2. 线程的亲和性
PTHREAD_SETAFFINITY_NP(3) Linux Programmer's Manual PTHREAD_SETAFFINITY_NP(3)
NAME
pthread_setaffinity_np, pthread_getaffinity_np - set/get CPU affinity of a thread
SYNOPSIS
#define _GNU_SOURCE
#include <pthread.h>
int pthread_setaffinity_np(pthread_t thread, size_t cpusetsize,
const cpu_set_t *cpuset);
int pthread_getaffinity_np(pthread_t thread, size_t cpusetsize,
cpu_set_t *cpuset);
Compile and link with -pthread.
DESCRIPTION
The pthread_setaffinity_np() sets the CPU affinity mask of the thread thread to the CPU set pointed to by cpuset. If the call is successful, and the thread is not currently running on one of the
CPUs in cpuset, then it is migrated to one of those CPUs.
The pthread_getaffinity_np() function returns the CPU affinity mask of the thread thread in the buffer pointed to by cpuset.
For more details on CPU affinity masks, see sched_setaffinity(2). For a description of a set of macros that can be used to manipulate and inspect CPU sets, see CPU_SET(3).
The argument cpusetsize is the length (in bytes) of the buffer pointed to by cpuset. Typically, this argument would be specified as sizeof(cpu_set_t). (It may be some other value, if using the
macros described in CPU_SET(3) for dynamically allocating a CPU set.)
RETURN VALUE
On success, these functions return 0; on error, they return a non-zero error number.
ERRORS
EFAULT A supplied memory address was invalid.
EINVAL (pthread_setaffinity_np()) The affinity bit mask mask contains no processors that are currently physically on the system and permitted to the thread according to any restrictions that may
be imposed by the "cpuset" mechanism described in cpuset(7).
EINVAL (pthread_setaffinity_np()) cpuset specified a CPU that was outside the set supported by the kernel. (The kernel configuration option CONFIG_NR_CPUS defines the range of the set supported
by the kernel data type used to represent CPU sets.)
EINVAL (pthread_getaffinity_np()) cpusetsize is smaller than the size of the affinity mask used by the kernel.
ESRCH No thread with the ID thread could be found.
VERSIONS
These functions are provided by glibc since version 2.3.4.