getrusage(3BSD) (BSD System Compatibility) getrusage(3BSD)
NAME
getrusage - (BSD) get information about resource utilization
SYNOPSIS
/usr/ucb/cc [flag . . . ] file . . .
#include <sys/time.h>
#include <sys/resource.h>
getrusage(int who, struct rusage *rusage);
DESCRIPTION
getrusage returns information about the resources utilized by
the current process, or all its terminated child processes.
The interpretation for some values reported, such as ru_idrss,
are dependent on the clock tick interval. This interval is an
implementation dependent value.
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.
Copyright 1994 Novell, Inc. Page 1
getrusage(3BSD) (BSD System Compatibility) getrusage(3BSD)
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 getpagesize(3BSD) system call).
Also, see NOTICES.
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 NOTICES.
ru_isrss Currently returns 0.
ru_minflt The number of page faults serviced which did
not require any physical I/O activity. Also,
see NOTICES.
ru_majflt The number of page faults serviced which
required physical I/O activity. This could
include page ahead operations by the kernel.
Also, see NOTICES.
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(2) request.
ru_oublock The number of times the file system had to
perform output in servicing a write(2) 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.
Copyright 1994 Novell, Inc. Page 2
getrusage(3BSD) (BSD System Compatibility) getrusage(3BSD)
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 VALUE
If successful, the value of the appropriate structure is
filled in, and 0 is returned. If the call fails, a -1 is
returned.
ERRORS
getrusage will fail if:
EINVAL The who parameter is not a valid value.
EFAULT The address specified by the rusage argument is not
in a valid portion of the process's address space.
Since System V Release 4 does not implement this function
directly as a system call, an invalid address (rusage)
argument may result in a core dump as opposed to returning
EFAULT.
REFERENCES
gettimeofday(3BSD), read(2), sar(1M), times(2), wait(3BSD),
write(2)
NOTICES
Only the timeval fields of struct rusage are supported in this
implementation.
The numbers ru_inblock and ru_oublock account only for real
I/O, and are approximate measures at best. Data supplied by
the caching mechanism 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.
Copyright 1994 Novell, Inc. Page 3
getrusage(3BSD) (BSD System Compatibility) getrusage(3BSD)
Page faults can be generated from a variety of sources and for
a variety of reasons. The customary cause for a page fault is
a direct reference 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(2) and
write(2) 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 physical 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 references 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(2) or write(2) to something that is in the page cache
will get a minor page fault(s) as well.
There is no way to obtain information about a child process
which has not yet terminated.
Copyright 1994 Novell, Inc. Page 4