NAME
getrusage
—
get information about resource
utilization
SYNOPSIS
#include
<sys/time.h>
#include <sys/resource.h>
#define RUSAGE_SELF 0
#define RUSAGE_CHILDREN -1
int
getrusage
(int
who, struct rusage
*rusage);
DESCRIPTION
getrusage
()
returns information describing the resources utilized by the current
process, or all its terminated child processes. The
who parameter is either
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.
- 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
Upon success, a value of zero is returned. Otherwise, -1 is returned and errno is set to indicate the error.
ERRORS
getrusage
() will fail if:
- [
EINVAL
] - The who parameter is not a valid value.
- [
EFAULT
] - The address specified by the rusage parameter is not in a valid part of the process address space.
SEE ALSO
HISTORY
The getrusage
() function call appeared in
4.2BSD.
BUGS
There is no way to obtain information about a child process that has not yet terminated.