getrusage.2: Description of maintained fields

[thirdparty/man-pages.git] / man2 / getrusage.2

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.\" 2004-11-16 -- mtk: the getrlimit.2 page, which formerly included
.\" coverage of getrusage(2), has been split, so that the latter is
.\" now covered in its own getrusage.2.  For older details of change
.\" history, etc., see getrlimit.2
.\"
.\" Modified 2004-11-16, mtk, Noted that the nonconformance
.\"	when SIGCHLD is being ignored is fixed in 2.6.9.
.\" 2008-02-22, Sripathi Kodi <sripathik@in.ibm.com>: Document RUSAGE_THREAD
.\" 2008-05-25, mtk, clarify RUSAGE_CHILDREN + other clean-ups.
.\"
.TH GETRUSAGE 2 2009-08-25 "Linux" "Linux Programmer's Manual"
.SH NAME
getrusage \- get resource usage
.SH SYNOPSIS
.B #include <sys/time.h>
.br
.B #include <sys/resource.h>
.sp
.BI "int getrusage(int " who ", struct rusage *" usage );
.SH DESCRIPTION
.PP
.BR getrusage ()
returns resource usage measures for
.IR who ,
which can be one of the following:
.TP
.B RUSAGE_SELF
Return resource usage statistics for the calling process,
which is the sum of resources used by all threads in the process.
.TP
.B RUSAGE_CHILDREN
Return resource usage statistics for all children of the
calling process that have terminated and been waited for.
These statistics will include the resources used by grandchildren,
and further removed descendants,
if all of the intervening descendants waited on their terminated children.
.TP
.BR RUSAGE_THREAD " (since Linux 2.6.26)"
Return resource usage statistics for the calling thread.
.PP
The resource usages are returned in the structure pointed to by
.IR usage ,
which has the following form:
.PP
.in +4n
.nf
struct rusage {
    struct timeval ru_utime; /* user time used */
    struct timeval ru_stime; /* system time used */
    long   ru_maxrss;        /* maximum resident set size */
    long   ru_ixrss;         /* integral shared 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 */
};
.fi
.in
.PP
Not all fields are completed; unmaintained fields are set to zero by
the kernel. The fields are interpreted as follows:
.TP
.I ru_utime
the total amount of time spent executing in user mode.
.TP
.I ru_stime
the total amount of time spent in the system executing on behalf
of the process(es).
.TP
.IR ru_maxrss " (unmaintained)"
.TP
.IR ru_ixrss " (unmaintained)"
.TP
.IR ru_idrss " (unmaintained)"
.TP
.IR ru_isrss " (unmaintained)"
.TP
.I ru_minflt
the number of page faults serviced without any I/O activity; here
I/O activity is avoided by \*(lqreclaiming\*(rq a page frame from
the list of pages awaiting reallocation.
.TP
.I ru_majflt
the number of page faults serviced that required I/O activity.
.TP
.IR ru_nswap  " (unmaintained)"
.TP
.IR ru_inblock " (since Linux 2.6.22)"
the number of times the file system had to perform input.
.TP
.IR ru_oublock " (since Linux 2.6.22)"
the number of times the file system had to perform output.
.TP
.IR ru_msgsnd " (unmaintained)"
.TP
.IR ru_msgrcv " (unmaintained)"
.TP
.IR ru_nsignals " (unmaintained)"
.TP
.IR ru_nvcsw " (since Linux 2.6)"
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).
.TP
.IR ru_nivcsw " (since Linux 2.6)"
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.
.PP
.SH "RETURN VALUE"
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EFAULT
.I usage
points outside the accessible address space.
.TP
.B EINVAL
.I who
is invalid.
.SH "CONFORMING TO"
SVr4, 4.3BSD.
POSIX.1-2001 specifies
.BR getrusage (),
but only specifies the fields
.I ru_utime
and
.IR ru_stime .

.B RUSAGE_THREAD
is Linux-specific.
.SH NOTES
Resource usage metrics are preserved across an
.BR execve (2).

Including
.I <sys/time.h>
is not required these days, but increases portability.
(Indeed,
.I struct timeval
is defined in
.IR <sys/time.h> .)
.PP
In Linux kernel versions before 2.6.9, if the disposition of
.B SIGCHLD
is set to
.B SIG_IGN
then the resource usages of child processes
are automatically included in the value returned by
.BR RUSAGE_CHILDREN ,
although POSIX.1-2001 explicitly prohibits this.
This nonconformance is rectified in Linux 2.6.9 and later.
.\" See the description of getrusage() in XSH.
.\" A similar statement was also in SUSv2.
.LP
The structure definition shown at the start of this page
was taken from 4.3BSD Reno.

See also the description of
.IR /proc/PID/stat
in
.BR proc (5).
.SH "SEE ALSO"
.BR clock_gettime (2),
.BR getrlimit (2),
.BR times (2),
.BR wait (2),
.BR wait4 (2),
.BR clock (3)