lib/libsys/getrusage.2

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.Dd May 1, 2010
.Dt GETRUSAGE 2
.Os
.Sh NAME
.Nm getrusage
.Nd get information about resource utilization
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/types.h
.In sys/time.h
.In sys/resource.h
.Fd "#define    RUSAGE_SELF      0"
.Fd "#define    RUSAGE_CHILDREN -1"
.Fd "#define    RUSAGE_THREAD   1"
.Ft int
.Fn getrusage "int who" "struct rusage *rusage"
.Sh DESCRIPTION
The
.Fn getrusage
system call
returns information describing the resources utilized by the current
thread, the current process, or all its terminated child processes.
The
.Fa who
argument is either
.Dv RUSAGE_THREAD ,
.Dv RUSAGE_SELF ,
or
.Dv RUSAGE_CHILDREN .
The buffer to which
.Fa rusage
points will be filled in with
the following structure:
.Bd -literal
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 */
};
.Ed
.Pp
The fields are interpreted as follows:
.Bl -tag -width ru_minfltaa
.It Fa ru_utime
the total amount of time spent executing in user mode.
.It Fa ru_stime
the total amount of time spent in the system executing on behalf
of the process(es).
.It Fa ru_maxrss
the maximum resident set size utilized (in kilobytes).
.It Fa ru_ixrss
an
.Dq 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.
Ticks are statistics clock ticks.
The statistics clock has a frequency of
.Fn sysconf _SC_CLK_TCK
ticks per second.
.It Fa 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).
.It Fa 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).
.It Fa ru_minflt
the number of page faults serviced without any I/O activity; here
I/O activity is avoided by
.Dq reclaiming
a page frame from
the list of pages awaiting reallocation.
.It Fa ru_majflt
the number of page faults serviced that required I/O activity.
.It Fa ru_nswap
the number of times a process was
.Dq swapped
out of main
memory.
.It Fa ru_inblock
the number of times the file system had to perform input.
.It Fa ru_oublock
the number of times the file system had to perform output.
.It Fa ru_msgsnd
the number of IPC messages sent.
.It Fa ru_msgrcv
the number of IPC messages received.
.It Fa ru_nsignals
the number of signals delivered.
.It Fa 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).
.It Fa 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.
.El
.Sh NOTES
The numbers
.Fa ru_inblock
and
.Fa 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.
.Sh RETURN VALUES
.Rv -std getrusage
.Sh ERRORS
The
.Fn getrusage
system call will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa who
argument is not a valid value.
.It Bq Er EFAULT
The address specified by the
.Fa rusage
argument is not in a valid part of the process address space.
.El
.Sh SEE ALSO
.Xr gettimeofday 2 ,
.Xr wait 2 ,
.Xr clocks 7
.Sh HISTORY
The
.Fn getrusage
system call appeared in
.Bx 4.2 .
The
.Dv RUSAGE_THREAD
facility first appeared in
.Fx 8.1 .
.Sh BUGS
There is no way to obtain information about a child process
that has not yet terminated.