third_party/grpc/src/core/support/cpu_linux.c

/*
 *
 * Copyright 2015, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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 */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif /* _GNU_SOURCE */

#include <grpc/support/port_platform.h>

#ifdef GPR_CPU_LINUX

#include <sched.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>

#include <grpc/support/cpu.h>
#include <grpc/support/log.h>
#include <grpc/support/sync.h>

static int ncpus = 0;

static void init_num_cpus() {
  /* This must be signed. sysconf returns -1 when the number cannot be
     determined */
  ncpus = (int)sysconf(_SC_NPROCESSORS_ONLN);
  if (ncpus < 1) {
    gpr_log(GPR_ERROR, "Cannot determine number of CPUs: assuming 1");
    ncpus = 1;
  }
}

unsigned gpr_cpu_num_cores(void) {
  static gpr_once once = GPR_ONCE_INIT;
  gpr_once_init(&once, init_num_cpus);
  return (unsigned)ncpus;
}

unsigned gpr_cpu_current_cpu(void) {
  int cpu = sched_getcpu();
  if (cpu < 0) {
    gpr_log(GPR_ERROR, "Error determining current CPU: %s\n", strerror(errno));
    return 0;
  }
  return (unsigned)cpu;
}

#endif /* GPR_CPU_LINUX */