mergerfs/libfuse/lib/cpu.cpp

/*
  ISC License

  Copyright (c) 2024, Antonio SJ Musumeci <trapexit@spawn.link>

  Permission to use, copy, modify, and/or distribute this software for any
  purpose with or without fee is hereby granted, provided that the above
  copyright notice and this permission notice appear in all copies.

  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

#include "cpu.hpp"
#include "fmt/core.h"

#include <pthread.h>
#include <sched.h>

#include <filesystem>
#include <fstream>


int
CPU::getaffinity(cpu_set_t *cpuset_)
{
  const pid_t pid = 0;
  CPU_ZERO(cpuset_);
  return sched_getaffinity(pid,
                           sizeof(cpu_set_t),
                           cpuset_);
}

int
CPU::setaffinity(const pthread_t  thread_id_,
                 cpu_set_t       *cpuset_)
{
  return pthread_setaffinity_np(thread_id_,
                                sizeof(cpu_set_t),
                                cpuset_);
}

int
CPU::setaffinity(const pthread_t thread_id_,
                 const int       cpu_)
{
  cpu_set_t cpuset;

  CPU_ZERO(&cpuset);
  CPU_SET(cpu_,&cpuset);

  return CPU::setaffinity(thread_id_,&cpuset);
}

int
CPU::setaffinity(const pthread_t     thread_id_,
                 const std::set<int> cpus_)
{
  cpu_set_t cpuset;

  CPU_ZERO(&cpuset);
  for(auto const cpu : cpus_)
    CPU_SET(cpu,&cpuset);

  return CPU::setaffinity(thread_id_,&cpuset);
}

static
std::filesystem::path
generate_cpu_core_id_path(const int cpu_id_)
{
  const std::filesystem::path basepath{"/sys/devices/system/cpu"};

  return basepath / fmt::format("cpu{}",cpu_id_) / "topology" / "core_id";
}

int
CPU::count()
{
  int rv;
  cpu_set_t cpuset;

  rv = CPU::getaffinity(&cpuset);
  if(rv < 0)
    return rv;

  return CPU_COUNT(&cpuset);
}

CPU::CPUVec
CPU::cpus()
{
  cpu_set_t cpuset;
  CPU::CPUVec cpuvec;

  CPU::getaffinity(&cpuset);

  for(int i = 0; i < CPU_SETSIZE; i++)
    {
      if(!CPU_ISSET(i,&cpuset))
        continue;

      cpuvec.push_back(i);
    }

  return cpuvec;
}

CPU::CPU2CoreMap
CPU::cpu2core()
{
  cpu_set_t cpuset;
  CPU::CPU2CoreMap c2c;

  CPU::getaffinity(&cpuset);

  for(int i = 0; i < CPU_SETSIZE; i++)
    {
      int core_id;
      std::ifstream ifs;
      std::filesystem::path path;

      if(!CPU_ISSET(i,&cpuset))
        continue;

      path = ::generate_cpu_core_id_path(i);

      ifs.open(path);
      if(!ifs)
        break;

      ifs >> core_id;

      c2c[i] = core_id;

      ifs.close();
    }

  return c2c;
}

CPU::Core2CPUsMap
CPU::core2cpus()
{
  cpu_set_t cpuset;
  CPU::Core2CPUsMap c2c;

  CPU::getaffinity(&cpuset);

  for(int i = 0; i < CPU_SETSIZE; i++)
    {
      int core_id;
      std::ifstream ifs;
      std::filesystem::path path;

      if(!CPU_ISSET(i,&cpuset))
        continue;

      path = ::generate_cpu_core_id_path(i);

      ifs.open(path);
      if(!ifs)
        break;

      ifs >> core_id;

      c2c[core_id].insert(i);

      ifs.close();
    }

  return c2c;
}