getrusage(3C) Standard C Library Functions getrusage(3C)NAMEgetrusage - get information about resource utilization
SYNOPSIS
#include <sys/resource.h>
int getrusage(int who, struct rusage *r_usage);
DESCRIPTION
The getrusage() function provides measures of the resources used by the
current process, its terminated and waited-for child processes, or the
current light weight process (LWP). If the value of the who argument
is RUSAGE_SELF, information is returned about resources used by the
current process. If the value of the who argument is RUSAGE_CHILDREN,
information is returned about resources used by the terminated and
waited-for children of the current process. If the child is never
waited for (for instance, if the parent has SA_NOCLDWAIT set or sets
SIGCHLD to SIG_IGN), the resource information for the child process is
discarded and not included in the resource information provided by
getrusage(). If the value of the who argument is RUSAGE_LWP, informa‐
tion is returned about resources used by the current LWP.
The r_usage argument is a pointer to an object of type struct rusage in
which the returned information is stored. The members of rusage are as
follows:
struct timeval ru_utime; /* user time used */
struct timeval ru_stime; /* system time used */
long ru_maxrss; /* maximum resident set size */
long ru_idrss; /* integral resident set size */
long ru_minflt; /* page faults not requiring physical I/O */
long ru_majflt; /* page faults requiring physical I/O */
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 structure members 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(3C) function). See the NOTES section of this
page.
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. It does not take
sharing into account. See the NOTES section of this
page.
ru_minflt The number of page faults serviced which did not
require any physical I/O activity. See the NOTES sec‐
tion of this page.
ru_majflt The number of page faults serviced which required phys‐
ical I/O activity. This could include page ahead opera‐
tions by the kernel. See the NOTES section of this
page.
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 out‐
put 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.
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
Upon successful completion, getrusage() returns 0. Otherwise, −1 is
returned and errno is set to indicate the error.
ERRORS
The getrusage() function will fail if:
EFAULT The address specified by the r_usage argument is not in
a valid portion of the process' address space.
EINVAL The who parameter is not a valid value.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOsar(1M), read(2), times(2), write(2), getpagesize(3C), gettimeof‐
day(3C), wait(3C), attributes(5), standards(5)NOTES
The ru_maxrss, ru_ixrss, ru_idrss, and ru_isrss members of the rusage
structure are set to 0 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 cache 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.
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 refer‐
ence 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) functions.
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(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.
SunOS 5.10 2 Jul 2004 getrusage(3C)
