android将线程绑定在指定CPU

linux下可以直接调用pthread_setaffinity_np，将当前线程绑定在具体的cpu上，而android该API被屏蔽了，需要调用sched这个系统API，详情见下面代码：

package nativelibs;

public class Affinity {
    static {
        System.loadLibrary("Affinity");
    }
    public static native void bindToCpu(int cpu);
}

void set_cur_thread_affinity(int mask) {
    int err, syscallres;
    pid_t pid = gettid();
    syscallres = syscall(__NR_sched_setaffinity, pid, sizeof(mask), &mask);
    if (syscallres) {
        err = errno;
        LOGE("Error in the syscall setaffinity: mask = %d, err=%d",mask,errno);
    }
    LOGD("tid = %d has setted affinity success",pid);
}

ok，具体的JNI代码如下：

#include <jni.h>
#include <android/log.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <pthread.h>
#include <sys/syscall.h>

#define TAG "Affinity"
#define DEBUG 1

#ifndef CPU_ZERO
#define CPU_SETSIZE 1024
#define __NCPUBITS  (8 * sizeof (unsigned long))
typedef struct
{
    unsigned long __bits[CPU_SETSIZE / __NCPUBITS];
} cpu_set_t;

#define CPU_SET(cpu, cpusetp) \
  ((cpusetp)->__bits[(cpu)/__NCPUBITS] |= (1UL << ((cpu) % __NCPUBITS)))
#define CPU_ZERO(cpusetp) \
  memset((cpusetp), 0, sizeof(cpu_set_t))
#else
#define CPU_SET(cpu,cpustep) ((void)0)
#define CPU_ZERO(cpu,cpustep) ((void)0)
#endif

#ifdef DEBUG
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG,TAG,__VA_ARGS__)
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,TAG,__VA_ARGS__)
#else
#define LOGD(...) ((void)0)
#define LOGE(...) ((void)0)
#endif

void set_cur_thread_affinity(int mask) {
    int err, syscallres;
    pid_t pid = gettid();
    syscallres = syscall(__NR_sched_setaffinity, pid, sizeof(mask), &mask);
    if (syscallres) {
        err = errno;
        LOGE("Error in the syscall setaffinity: mask = %d, err=%d",mask,errno);
    }
    LOGD("tid = %d has setted affinity success",pid);
}

static int getCores() {
    return sysconf(_SC_NPROCESSORS_CONF);
}

JNIEXPORT int JNICALL Java_nativelibs_Affinity_getCores(JNIEnv *env, jclass type) {
    return getCores();
}

JNIEXPORT void JNICALL Java_nativelibs_Affinity_bindToCpu(JNIEnv *env, jclass type, jint cpu) {
    int cores = getCores();
    LOGD("get cpu number = %d\n",cores);
    if (cpu >= cores) {
        LOGE("your set cpu is beyond the cores,exit...");
        return;
    }

    cpu_set_t mask;
    CPU_ZERO(&mask);
    CPU_SET(cpu,&mask);
    set_cur_thread_affinity((int)(&mask));
    LOGD("set affinity to %d success",cpu);
}