message: resctrl: be more verbose in case of file read error
diff: @@ -116,6 +116,16 @@ namespace pcm
  {
  result += atoll(data.c_str());
  }
  + else
  + {
  + static std::mutex lock;
  + std::lock_guard<std::mutex> _(lock);
  + std::cerr << "Error reading " << f << ". Error: " << strerror(errno) << "\n";
  + if (errno == 24)
  + {
  + std::cerr << "try executing 'ulimit -n 10000' to increase the limit on the number of open files.\n";
  + }
  + }
  }
  return result;
  }
  