getrusage and the data type
are used to examine the resource usage of a process. They are declared
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
This function reports resource usage totals for processes specified by
processes, storing the information in
In most systems, processes has only two valid values:
Just the current process.
All child processes (direct and indirect) that have already terminated.
The return value of
getrusage is zero for success, and
The argument processes is not valid.
One way of getting resource usage for a particular child process is with
wait4, which returns totals for a child when it
terminates. See BSD Process Wait Function.
This data type stores various resource usage statistics. It has the following members, and possibly others:
struct timeval ru_utime
Time spent executing user instructions.
struct timeval ru_stime
Time spent in operating system code on behalf of processes.
long int ru_maxrss
The maximum resident set size used, in kilobytes. That is, the maximum number of kilobytes of physical memory that processes used simultaneously.
long int ru_ixrss
An integral value expressed in kilobytes times ticks of execution, which indicates the amount of memory used by text that was shared with other processes.
long int ru_idrss
An integral value expressed the same way, which is the amount of unshared memory used for data.
long int ru_isrss
An integral value expressed the same way, which is the amount of unshared memory used for stack space.
long int ru_minflt
The number of page faults which were serviced without requiring any I/O.
long int ru_majflt
The number of page faults which were serviced by doing I/O.
long int ru_nswap
The number of times processes was swapped entirely out of main memory.
long int ru_inblock
The number of times the file system had to read from the disk on behalf of processes.
long int ru_oublock
The number of times the file system had to write to the disk on behalf of processes.
long int ru_msgsnd
Number of IPC messages sent.
long int ru_msgrcv
Number of IPC messages received.
long int ru_nsignals
Number of signals received.
long int ru_nvcsw
The number of times processes voluntarily invoked a context switch (usually to wait for some service).
long int ru_nivcsw
The number of times an involuntary context switch took place (because a time slice expired, or another process of higher priority was scheduled).