getrusage() returns information describing the resources used by the current process, or all its terminated child processes. The
who parameter is either
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 */
long ru_maxrss; /* max resident set size */
long ru_ixrss; /* integral shared text memory size */
long ru_idrss; /* integral unshared data size */
long ru_isrss; /* integral unshared stack size */
long ru_minflt; /* page reclaims */
long ru_majflt; /* page faults */
long ru_nswap; /* swaps */
long ru_inblock; /* block input operations */
long ru_oublock; /* block output operations */
long ru_msgsnd; /* messages sent */
long ru_msgrcv; /* messages received */
long ru_nsignals; /* signals received */
long ru_nvcsw; /* voluntary context switches */
long ru_nivcsw; /* involuntary context switches */
};
The fields are interpreted as follows:
ru_utime
the total amount of time spent executing in user mode.
ru_stime
the total amount of time spent in the system executing on behalf of the process(es).
ru_maxrss
the maximum resident set size used (in kilobytes).
ru_ixrss
an “integral” value indicating the amount of memory used by the text segment that was also shared among other processes. This value is expressed in units of kilobytes * ticks-of-execution.
ru_idrss
an integral value of the amount of unshared memory residing in the data segment of a process (expressed in units of kilobytes * ticks-of-execution).
ru_isrss
an integral value of the amount of unshared memory residing in the stack segment of a process (expressed in units of kilobytes * ticks-of-execution).
ru_minflt
the number of page faults serviced without any I/O activity; here I/O activity is avoided by “reclaiming” a page frame from the list of pages awaiting reallocation.
ru_majflt
the number of page faults serviced that required I/O activity.
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.
ru_oublock
the number of times the file system had to perform output.
ru_msgsnd
the number of IPC messages sent.
ru_msgrcv
the number of IPC messages received.
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.