Is getrusage broken in Linux (2.6.30)

Question

This code

 void print_usage(char * msg)
{
    struct rusage usage;
    getrusage(RUSAGE_SELF, &usage);
    printf("Limits: %s\n", msg);
    printf("  %s, %li\n",  " maximum resident set size "    , usage.ru_maxrss  );
    printf("  %s, %li\n",  " integral shared memory size "  , usage.ru_ixrss   );
    printf("  %s, %li\n",  " integral unshared data size "  , usage.ru_idrss   );
    printf("  %s, %li\n",  " integral unshared stack size " , usage.ru_isrss   );
    printf("  %s, %li\n",  " page reclaims "                , usage.ru_minflt  );
    printf("  %s, %li\n",  " page faults "                  , usage.ru_majflt  );
    printf("  %s, %li\n",  " swaps "                        , usage.ru_nswap   );
    printf("  %s, %li\n",  " block input operations "       , usage.ru_inblock );
    printf("  %s, %li\n",  " block output operations "      , usage.ru_oublock );
    printf("  %s, %li\n",  " messages sent "                , usage.ru_msgsnd  );
    printf("  %s, %li\n",  " messages received "            , usage.ru_msgrcv  );
    printf("  %s, %li\n",  " signals received "             , usage.ru_nsignals);
    printf("  %s, %li\n",  " voluntary context switches "   , usage.ru_nvcsw   );
    printf("  %s, %li\n",  " involuntary context switches " , usage.ru_nivcsw  );

}

reports only zeroes for many fields, even if I use it in rather big program (after jvm start)

   maximum resident set size , 0
   integral shared memory size , 0
   integral unshared data size , 0
   integral unshared stack size , 0
   page reclaims , 2514
   page faults , 0
   swaps , 0
   block input operations , 0
   block output operations , 0
   messages sent , 0
   messages received , 0
   signals received , 0
   voluntary context switches , 137
   involuntary context switches , 1

The non-zero fields are "*vcsw", "*flt".

All *rss, *swap, msg*, *block, *signals are Zero.

Is there something broken?

Linux is x86 2.6.30.

Trophy

Answer 1

Yes it is partly broken. Not all fields are filled by kernel. http://www.kernel.org/doc/man-pages/online/pages/man2/getrusage.2.html

Working fields:

   ru_utime
   ru_stime
   ru_maxrss (since Linux 2.6.32)
   ru_minflt
   ru_majflt
   ru_inblock (since Linux 2.6.22)
   ru_oublock (since Linux 2.6.22)
   ru_nvcsw (since Linux 2.6)
   ru_nivcsw (since Linux 2.6)

Unused fields:

   ru_ixrss (unmaintained)
   ru_idrss (unmaintained)
   ru_isrss (unmaintained)
   ru_nswap (unmaintained)
   ru_msgsnd (unmaintained)
   ru_msgrcv (unmaintained)
   ru_nsignals (unmaintained)

Trophy

But what function(s) should one use, then, to track memory usage under Linux? – Greenbrier

something like system("cat /proc/pid/stat") (or manually open and read files in /proc/pid/, e.g. maps or smaps), as ps` uses. Also, maxrss works in newer kernel. Also, there is a malloc_stats and external tracers. – Trophy