getrusage2

Usage

Library

Standard C Library (libc, -lc)

Overview

The getrusage() system call returns information describing the resources utilized by the current thread, the current process, or all its terminated child processes. The who argument is either RUSAGE_THREAD, 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 utilized (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. Ticks are statistics clock ticks. The statistics clock has a frequency of sysconf(_SC_CLK_TCK) ticks per second.

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.

Notes

The numbers ru_inblock and ru_oublock account only for real I/O; data supplied by the caching mechanism is charged only to the first process to read or write the data.

Return values

The getrusage() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

Errors

The getrusage() system call will fail if:

[EINVAL]

The who argument is not a valid value.

[EFAULT]

The address specified by the rusage argument is not in a valid part of the process address space.