Resource Usage (The GNU C Library)

22.1 Resource Usage

The function getrusage and the data type struct rusage are used to examine the resource usage of a process. They are declared in sys/resource.h.

Function: int getrusage (int processes, struct rusage *rusage) ¶

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 *rusage.

In most systems, processes has only two valid values:

RUSAGE_SELF ¶: Just the current process.
RUSAGE_CHILDREN ¶: All child processes (direct and indirect) that have already terminated.

The return value of getrusage is zero for success, and -1 for failure.

EINVAL: The argument processes is not valid.

One way of getting resource usage for a particular child process is with the function wait4, which returns totals for a child when it terminates. See BSD Process Wait Function.

Data Type: struct rusage ¶

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).