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The function getrusage and the data type struct rusage
are used for examining the usage figures of a process. They are declared
in `sys/resource.h'.
- Function: int getrusage (int processes, struct rusage *rusage)
-
This function reports the 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 terminated already.
In the GNU system, you can also inquire about a particular child process
by specifying its process ID.
The return value of getrusage is zero for success, and -1
for failure.
EINVAL
-
The argument processes is not valid.
One way of getting usage figures for a particular child process is with
the function wait4, which returns totals for a child when it
terminates. See section BSD Process Wait Functions.
- Data Type: struct rusage
-
This data type records a collection usage amounts for various sorts of
resources. 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 that processes used in real memory 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 in data.
long int ru_isrss
-
An integral value expressed the same way, which is the amount of
unshared memory used in 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 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
the time slice expired, or another process of higher priority became
runnable).
An additional historical function for examining usage figures,
vtimes, is supported but not documented here. It is declared in
`sys/vtimes.h'.
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