LinuxProcData.h

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#ifndef art_Utilities_LinuxProcData_h
#define art_Utilities_LinuxProcData_h

//===================================================================
//
// LinuxProcData
//
//-----------------------------------------------
//
// This is a helper class for storing information that is available
// via 'cat /proc/PID/stat'.  As of SLF6.5 (Ramsey), the values from
// that command correspond to (see 'man 5 proc'):
//
//        Property              type   C++ type
//     ===============================================
//     1. pid                    %d    int
//     2. comm                   %s    char[400]
//     3. state                  %c    char
//     4. ppid                   %d    int
//     5. pgrp                   %d    int
//     6. session                %d    int
//     7. tty_nr                 %d    int
//     8. tpgid                  %d    int
//     9. flags                  %u    unsigned
//    10. minflt                 %lu   unsigned long
//    11. cminflt                %lu   unsigned long
//    12. majflt                 %lu   unsigned long
//    13. cmajflt                %lu   unsigned long
//    14. utime                  %lu   unsigned long
//    15. stime                  %lu   unsigned long
//    16. cutime                 %ld   long
//    17. cstime                 %ld   long
//    18. priority               %ld   long
//    19. nice                   %ld   long
//    20. num_threads            %ld   long
//    21. itrealvalue            %ld   long
//    22. starttime              %llu  unsigned long long
//    23. vsize                  %lu   unsigned long
//    24. rss                    %ld   long
//    25. rsslim                 %lu   unsigned long
//    26. startcode              %lu   unsigned long
//    27. endcode                %lu   unsigned long
//    28. startstack             %lu   unsigned long
//    29. kstkesp                %lu   unsigned long
//    30. kstkeip                %lu   unsigned long
//    31. signal                 %lu   unsigned long
//    32. blocked                %lu   unsigned long
//    33. sigignore              %lu   unsigned long
//    34. sigcatch               %lu   unsigned long
//    35. wchan                  %lu   unsigned long
//    36. nswap                  %lu   unsigned long
//    37. cnswap                 %lu   unsigned long
//    38. exit_signal            %d    int
//    39. processor              %d    int
//    40. rt_priority            %u    unsigned
//    41. policy                 %u    unsigned
//    42. delayacct_blkio_ticks  %llu  unsigned long long
//    43. guest_time             %lu   unsigned long
//    44. cguest_time            %ld   long
//
// Currently, we are interested only in 'vsize' and 'rss'.
//
//===================================================================

#include <sstream>
#include <tuple>
#include <type_traits>

namespace art {

  struct LinuxProcData {

    // supported procfs types
    enum procfs_type { VSIZE, RSS, ntypes };

    // aliases
    struct proc_type {};
    struct vsize_t : proc_type {
      using value_type = unsigned long;
      explicit vsize_t(value_type const v) : value{v} {}
      value_type value;
    };

    struct rss_t : proc_type {
      using value_type = long;
      explicit rss_t(value_type const v) : value{v} {}
      value_type value;
    };

    using proc_tuple = std::tuple<vsize_t, rss_t>;

    static auto
    make_proc_tuple(vsize_t::value_type const vsize = {},
                    rss_t::value_type const rss = {})
    {
      return proc_tuple{vsize_t{vsize}, rss_t{rss}};
    }

    template <typename T>
    static std::enable_if_t<std::is_base_of<proc_type, T>::value, double>
    getValueInMB(proc_tuple const& t)
    {
      // Info from proc is in bytes; convert to base-10 MB.
      return std::get<T>(t).value / MB;
    }

    // constants
    static constexpr double KB{1000.};
    static constexpr double KiB{1.024 * KB};
    static constexpr double MB{KB * KB};
    static constexpr double MiB{KiB * KiB};
  };

} // namespace art
#endif /* art_Utilities_LinuxProcData_h */

// Local variables:
// mode:c++
// End: