getrusage - get resource usage
Standard C library (
libc,
-lc)
#include <sys/resource.h>
int getrusage(int who, struct rusage *usage);
getrusage() returns resource usage measures for
who, which can be
one of the following:
- RUSAGE_SELF
- Return resource usage statistics for the calling process,
which is the sum of resources used by all threads in the process.
- 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.
-
RUSAGE_THREAD (since Linux 2.6.26)
- Return resource usage statistics for the calling thread.
The _GNU_SOURCE feature test macro must be defined (before
including any header file) in order to obtain the definition of
this constant from <sys/resource.h>.
The resource usages are returned in the structure pointed to by
usage,
which has the following form:
struct rusage {
struct timeval ru_utime; /* user CPU time used */
struct timeval ru_stime; /* system CPU 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 (soft page faults) */
long ru_majflt; /* page faults (hard page faults) */
long ru_nswap; /* swaps */
long ru_inblock; /* block input operations */
long ru_oublock; /* block output operations */
long ru_msgsnd; /* IPC messages sent */
long ru_msgrcv; /* IPC messages received */
long ru_nsignals; /* signals received */
long ru_nvcsw; /* voluntary context switches */
long ru_nivcsw; /* involuntary context switches */
};
Not all fields are completed; unmaintained fields are set to zero by the kernel.
(The unmaintained fields are provided for compatibility with other systems,
and because they may one day be supported on Linux.) The fields are
interpreted as follows:
- ru_utime
- This is the total amount of time spent executing in user
mode, expressed in a timeval structure (seconds plus
microseconds).
- ru_stime
- This is the total amount of time spent executing in kernel
mode, expressed in a timeval structure (seconds plus
microseconds).
-
ru_maxrss (since Linux 2.6.32)
- This is the maximum resident set size used (in kilobytes).
For RUSAGE_CHILDREN, this is the resident set size of the largest
child, not the maximum resident set size of the process tree.
-
ru_ixrss (unmaintained)
- This field is currently unused on Linux.
-
ru_idrss (unmaintained)
- This field is currently unused on Linux.
-
ru_isrss (unmaintained)
- This field is currently unused on Linux.
- 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 (unmaintained)
- This field is currently unused on Linux.
-
ru_inblock (since Linux 2.6.22)
- The number of times the filesystem had to perform
input.
-
ru_oublock (since Linux 2.6.22)
- The number of times the filesystem had to perform
output.
-
ru_msgsnd (unmaintained)
- This field is currently unused on Linux.
-
ru_msgrcv (unmaintained)
- This field is currently unused on Linux.
-
ru_nsignals (unmaintained)
- This field is currently unused on Linux.
-
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).
-
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.
On success, zero is returned. On error, -1 is returned, and
errno is set
to indicate the error.
- EFAULT
-
usage points outside the accessible address
space.
- EINVAL
-
who is invalid.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
getrusage () |
Thread safety |
MT-Safe |
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. POSIX.1 specifies
getrusage(),
but specifies only the fields
ru_utime and
ru_stime.
RUSAGE_THREAD is Linux-specific.
Resource usage metrics are preserved across an
execve(2).
Before Linux 2.6.9, if the disposition of
SIGCHLD is set to
SIG_IGN then the resource usages of child processes are automatically
included in the value returned by
RUSAGE_CHILDREN, although
POSIX.1-2001 explicitly prohibits this. This nonconformance is rectified in
Linux 2.6.9 and later.
The structure definition shown at the start of this page was taken from 4.3BSD
Reno.
Ancient systems provided a
vtimes() function with a similar purpose to
getrusage(). For backward compatibility, glibc (up until Linux 2.32)
also provides
vtimes(). All new applications should be written using
getrusage(). (Since Linux 2.33, glibc no longer provides an
vtimes() implementation.)
See also the description of
/proc/pid
/stat in
proc(5).
clock_gettime(2),
getrlimit(2),
times(2),
wait(2),
wait4(2),
clock(3)