Java-Thread-Affinity/affinity/src/main/c/software_chronicle_enterprise_internals_impl_NativeAffinity.cpp at 7e93aa7ab4bca5727513c54134259cf028c2ab9f · OpenHFT/Java-Thread-Affinity · GitHub

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/**
 * Copyright 2013-2026 chronicle.software; SPDX-License-Identifier: Apache-2.0
 */
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif

#include <jni.h>
#ifdef __linux__
  #include <sched.h>
  #include <sys/syscall.h>
  #include <sys/types.h>
  #include <unistd.h>
  #include <string.h>
#endif
#include <stdexcept>
#include "software_chronicle_enterprise_internals_impl_NativeAffinity.h"

/*
 * Class:     software_chronicle_enterprise_internals_impl_NativeAffinity
 * Method:    getAffinity0
 * Signature: ()J
 */
JNIEXPORT jbyteArray JNICALL Java_software_chronicle_enterprise_internals_impl_NativeAffinity_getAffinity0
  (JNIEnv *env, jclass c)
{
#ifdef __linux__
    // The default size of the structure supports 1024 CPUs, should be enough
    // for now In the future we can use dynamic sets, which can support more
    // CPUs, given OS can handle them as well
    cpu_set_t mask;
    const size_t size = sizeof(mask);

    int res = sched_getaffinity(0, size, &mask);
    if (res < 0)
    {
        return NULL;
    }

    jbyteArray ret = env->NewByteArray(size);
    jbyte* bytes = env->GetByteArrayElements(ret, 0);
    memcpy(bytes, &mask, size);
    env->SetByteArrayRegion(ret, 0, size, bytes);

    return ret;
#else
    throw std::runtime_error("Not supported");
#endif
}

/*
 * Class:     software_chronicle_enterprise_internals_NativeAffinity
 * Method:    setAffinity0
 * Signature: (J)V
 */
JNIEXPORT void JNICALL Java_software_chronicle_enterprise_internals_impl_NativeAffinity_setAffinity0
  (JNIEnv *env, jclass c, jbyteArray affinity)
{
#ifdef __linux__
    cpu_set_t mask;
    const size_t size = sizeof(mask);
    CPU_ZERO(&mask);

    jbyte* bytes = env->GetByteArrayElements(affinity, 0);
    memcpy(&mask, bytes, size);

    sched_setaffinity(0, size, &mask);
#else
    throw std::runtime_error("Not supported");
#endif
}

/*
 * Class:     software_chronicle_enterprise_internals_impl_NativeAffinity
 * Method:    getProcessId0
 * Signature: ()I
 */
JNIEXPORT jint JNICALL Java_software_chronicle_enterprise_internals_impl_NativeAffinity_getProcessId0
  (JNIEnv *env, jclass c) {
#ifndef __linux__
    throw std::runtime_error("Not supported");
#else

  return (jint) getpid();
#endif
}

/*
 * Class:     software_chronicle_enterprise_internals_impl_NativeAffinity
 * Method:    getThreadId0
 * Signature: ()I
 */
JNIEXPORT jint JNICALL Java_software_chronicle_enterprise_internals_impl_NativeAffinity_getThreadId0
  (JNIEnv *env, jclass c) {
#ifndef __linux__
    throw std::runtime_error("Not supported");
#else

    return (jint) (pid_t) syscall (SYS_gettid);
#endif
}

/*
 * Class:     software_chronicle_enterprise_internals_impl_NativeAffinity
 * Method:    getCpu0
 * Signature: ()I
 */
JNIEXPORT jint JNICALL Java_software_chronicle_enterprise_internals_impl_NativeAffinity_getCpu0
  (JNIEnv *env, jclass c) {
#ifndef __linux__
    throw std::runtime_error("Not supported");
#else

  return (jint) sched_getcpu();
#endif
}