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GETRUSAGE(2)                  System Calls Manual                 GETRUSAGE(2)



NAME
       getrusage - get information about resource utilization

SYNOPSIS
       #include <&lt;sys/time.h>&gt;
       #include <&lt;sys/resource.h>&gt;

       int getrusage(who, rusage)
       int who;
       struct rusage *rusage;

DESCRIPTION
       getrusage()  returns  information  about  the resources utilized by the
       current process, or all its terminated child processes.  The  interpre-
       tation for some values reported, such as ru_idrss, are dependent on the
       clock tick interval.  This  interval  is  an  implementation  dependent
       value;  for example, on Sun-3 sytems the clock tick interval is 1/50 of
       a second, while on Sun-4 systems the clock tick interval is 1/100 of  a
       second.

       The who parameter is one of RUSAGE_SELF or RUSAGE_CHILDREN.  The buffer
       to which rusage points will be filled in with the following structure:

              struct    rusage {
                   struct timeval ru_utime;      /* user time used */
                   struct timeval ru_stime;      /* system time used */
                   int  ru_maxrss;          /* maximum resident set size */
                   int  ru_ixrss;      /* currently 0 */
                   int  ru_idrss;      /* integral resident set size */
                   int  ru_isrss;      /* currently 0 */
                   int  ru_minflt;          /* page faults not requiring physical I/O */
                   int  ru_majflt;          /* page faults requiring physical I/O */
                   int  ru_nswap;      /* swaps */
                   int  ru_inblock;         /* block input operations */
                   int  ru_oublock;         /* block output operations */
                   int  ru_msgsnd;          /* messages sent */
                   int  ru_msgrcv;          /* messages received */
                   int  ru_nsignals;        /* signals received */
                   int  ru_nvcsw;      /* voluntary context switches */
                   int  ru_nivcsw;          /* involuntary context switches */
              };

       The fields are interpreted as follows:

       ru_utime       The total amount of time spent executing in  user  mode.
                      Time is given in seconds and microseconds.

       ru_stime       The total amount of time spent executing in system mode.
                      Time is given in seconds and microseconds.

       ru_maxrss      The maximum resident set size.  Size is given  in  pages
                      (the  size of a page, in bytes, is given by the getpage-
                      size(2) system call).  Also, see WARNINGS.

       ru_ixrss       Currently returns 0.

       ru_idrss       An "integral" value indicating the amount of  memory  in
                      use  by  a  process  while the process is running.  This
                      value is the sum  of  the  resident  set  sizes  of  the
                      process  running when a clock tick occurs.  The value is
                      given in pages times clock ticks.   Note:  it  does  not
                      take sharing into account.  Also, see WARNINGS.

       ru_isrss       Currently returns 0.

       ru_minflt      The number of page faults serviced which did not require
                      any physical I/O activity.  Also, see WARNINGS.

       ru_majflt      The number of page faults serviced which required physi-
                      cal  I/O activity.  This could include page ahead opera-
                      tions by the kernel.  Also, see WARNINGS.

       ru_nswap       The number of times a process was swapped  out  of  main
                      memory.

       ru_inblock     The number of times the file system had to perform input
                      in servicing a read(2V) request.

       ru_oublock     The number of times the file system had to perform  out-
                      put in servicing a write(2V) request.

       ru_msgsnd      The number of messages sent over sockets.

       ru_msgrcv      The number of messages received from sockets.

       ru_nsignals    The number of signals delivered.

       ru_nvcsw       The  number  of times a context switch resulted due to a
                      process voluntarily giving up the processor  before  its
                      time  slice was completed (usually to await availability
                      of a resource).

       ru_nivcsw      The number of times a context switch resulted due  to  a
                      higher priority process becoming runnable or because the
                      current process exceeded its time slice.

RETURN VALUES
       getrusage() returns:

       0      on success.

       -1     on failure and sets errno to indicate the error.

ERRORS
       EFAULT         The address specified by the rusage argument is not in a
                      valid portion of the process's address space.

       EINVAL         The who parameter is not a valid value.

SEE ALSO
       gettimeofday(2), read(2V), wait(2V), write(2V)

WARNINGS
       The  numbers  ru_inblock  and ru_oublock account only for real I/O, and
       are approximate measures at best.  Data supplied by the caching  mecha-
       nism  is charged only to the first process to read and the last process
       to write the data.

       The way resident set size is calculated is an approximation, and  could
       misrepresent the true resident set size.

       Page  faults can be generated from a variety of sources and for a vari-
       ety of reasons.  The customary cause for a page fault is a direct  ref-
       erence  by the program to a page which is not in memory.  Now, however,
       the kernel can generate page faults on behalf of the user, for example,
       servicing  read(2V) and write(2V) system calls.  Also, a page fault can
       be caused by an absent hardware translation to a page, even though  the
       page is in physical memory.

       In  addition  to  hardware  detected  page faults, the kernel may cause
       pseudo page faults in order to perform some housekeeping.  For example,
       the  kernel may generate page faults, even if the pages exist in physi-
       cal memory, in order to lock down pages involved in a raw I/O request.

       By definition, major page faults require physical I/O, while minor page
       faults  do  not require physical I/O.  For example, reclaiming the page
       from the free list would avoid I/O and generate  a  minor  page  fault.
       More commonly, minor page faults occur during process startup as refer-
       ences to pages which are already in memory.  For example, if an address
       space  faults  on some "hot" executable or shared library, this results
       in a minor page fault for the address space.  Also,  any  one  doing  a
       read(2V) or write(2V) to something that is in the page cache will get a
       minor page fault(s) as well.

BUGS
       There is no way to obtain information about a child process  which  has
       not yet terminated.



                                21 January 1990                   GETRUSAGE(2)