len | parseCPUInfo() | HWTopoLinux.cpp

[MohsenKoohi]

The buffer size for reading topology in https://github.com/IntelligentSoftwareSystems/Galois/blob/master/libgalois/src/HWTopoLinux.cpp#L103 is small on some architectures. The flags line on /proc/cpuinfo can contain more than 1024 chars.

[askoldvilkha]

a comment from a Galois user, NOT a developer. I happened to run into the same issue quite recently. Here's the fix that worked for me. It also provides more information on what was parsed from /proc/cpuinfo into the number of available cores in Galois.

Fix:

Inside Galois/libgalois/src/HWTopoLinux.cpp after line 99 (//! Parse /proc/cpuinfo), change the original parseCPUInfo() function to:

std::vector<cpuinfo> parseCPUInfo() {
  std::vector<cpuinfo> vals;

  std::ifstream procInfo("/proc/cpuinfo");
  if (!procInfo)
    GALOIS_SYS_DIE("failed opening /proc/cpuinfo");

  int cur = -1;
  std::string line;

  while (std::getline(procInfo, line)) {
    int num;
    if (sscanf(line.c_str(), "processor : %d", &num) == 1) {
      assert(cur < num);
      cur = num;
      vals.resize(cur + 1);
      vals.at(cur).proc = num;
    } else if (sscanf(line.c_str(), "physical id : %d", &num) == 1) {
      vals.at(cur).physid = num;
    } else if (sscanf(line.c_str(), "siblings : %d", &num) == 1) {
      vals.at(cur).sib = num;
    } else if (sscanf(line.c_str(), "core id : %d", &num) == 1) {
      vals.at(cur).coreid = num;
    } else if (sscanf(line.c_str(), "cpu cores : %d", &num) == 1) {
      vals.at(cur).cpucores = num;
    }
  }

  for (auto& c : vals)
    c.numaNode = getNumaNode(c);

  return vals;
}

Optional (if you want to see what Galois parsed): add cout after calling parseCPUInfo() in line 218. Replace lines 219-221 with:

 std::cout << "[HWTopo] parseCPUInfo returned " << info.size() << " entries\n";

  std::sort(info.begin(), info.end());
  markSMT(info);
  markValid(info);

  size_t validCount = std::count_if(info.begin(), info.end(), [](const cpuinfo& c){ return c.valid; });
  std::cout << "[HWTopo] after markValid: " << validCount << "/" << info.size() << " valid\n";

  // print cpuset
  auto cpuset = parseCPUSet();
  std::cout << "[HWTopo] cpuset size=" << cpuset.size() << ": ";
  for (int x : cpuset) std::cout << x << " ";
  std::cout << "\n";

And add this line before the return line 260:
std::cout << "[HWTopo] maxThreads=" << retMTI.maxThreads << " maxCores=" << retMTI.maxCores << "\n";

Example output:

[HWTopo] parseCPUInfo returned 16 entries
[HWTopo] after markValid: 16/16 valid
[HWTopo] cpuset size=16: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 
[HWTopo] maxThreads=16 maxCores=8