utils.cpp

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

#include "cpu_types.hpp"

void init_cpu_threads_env(const std::string& cpu_ids) {
  bitmask* omp_cpu_mask = numa_parse_cpustring(cpu_ids.c_str());
  TORCH_CHECK(omp_cpu_mask->size > 0);
  std::vector<int> omp_cpu_ids;
  omp_cpu_ids.reserve(omp_cpu_mask->size);

  constexpr int group_size = 8 * sizeof(*omp_cpu_mask->maskp);

  for (int offset = 0; offset < omp_cpu_mask->size; offset += group_size) {
    unsigned long group_mask = omp_cpu_mask->maskp[offset / group_size];
    int i = 0;
    while (group_mask) {
      if (group_mask & 1) {
        omp_cpu_ids.emplace_back(offset + i);
      }
      ++i;
      group_mask >>= 1;
    }
  }

  // Memory node binding
  if (numa_available() != -1) {
    int mem_node_id = numa_node_of_cpu(omp_cpu_ids.front());
    bitmask* mask = numa_parse_nodestring(std::to_string(mem_node_id).c_str());
    bitmask* src_mask = numa_get_membind();

    int pid = getpid();

    // move all existing pages to the specified numa node.
    *(src_mask->maskp) = *(src_mask->maskp) ^ *(mask->maskp);
    int page_num = numa_migrate_pages(pid, src_mask, mask);
    if (page_num == -1) {
      TORCH_CHECK(false,
                  "numa_migrate_pages failed. errno: " + std::to_string(errno));
    }

    // restrict memory allocation node.
    numa_set_membind(mask);
    numa_set_strict(1);
  }

  // OMP threads binding
  omp_set_num_threads((int)omp_cpu_ids.size());
  torch::set_num_threads((int)omp_cpu_ids.size());
  TORCH_CHECK_EQ(omp_cpu_ids.size(), torch::get_num_threads());
  TORCH_CHECK_EQ(omp_cpu_ids.size(), omp_get_max_threads());
#pragma omp parallel for schedule(static, 1)
  for (size_t i = 0; i < omp_cpu_ids.size(); ++i) {
    cpu_set_t* mask = CPU_ALLOC(omp_cpu_mask->size);
    size_t size = CPU_ALLOC_SIZE(omp_cpu_mask->size);
    CPU_ZERO_S(size, mask);
    CPU_SET_S(omp_cpu_ids[i], size, mask);
    sched_setaffinity(0, sizeof(cpu_set_t), mask);
    CPU_FREE(mask);
  }

  numa_free_nodemask(omp_cpu_mask);
}