/ 
BSD-Resource-1.06
River stage two • 16 direct dependents • 37 total dependents
/ BSD::Resource

NAME

BSD::Resource - BSD process resource limit and priority functions

SYNOPSIS

use BSD::Resource;

#
# the process resource consumption so far
#

($usertime, $systemtime,
 $maxrss, $ixrss, $idrss, $isrss, $minflt, $majflt, $nswap,
 $inblock, $oublock, $msgsnd, $msgrcv,
 $nsignals, $nvcsw, $nivcsw) = getrusage($ru_who);

$rusage = getrusage($ru_who);

#
# the process resource limits
#

($nowsoft, $nowhard) = getrlimit($resource);

$rlimit = getrlimit($resource);

$success = setrlimit($resource, $newsoft, $newhard);

#
# the process scheduling priority
#

$nowpriority = getpriority($pr_which, $pr_who);

$success = setpriority($pr_which, $pr_who, $priority);

# The following is not a BSD function.
# It is a Perlish utility for the users of BSD::Resource.

$rlimits = get_rlimits();

DESCRIPTION

getrusage

($usertime, $systemtime,
 $maxrss, $ixrss, $idrss, $isrss, $minflt, $majflt, $nswap,
 $inblock, $oublock, $msgsnd, $msgrcv,
 $nsignals, $nvcsw, $nivcsw) = getrusage($ru_who);

$rusage = getrusage($ru_who);

# $ru_who argument is optional; it defaults to RUSAGE_SELF

$rusage = getrusage();

The $ru_who argument is either RUSAGE_SELF (the current process) or RUSAGE_CHILDREN (all the child processes of the current process) or it maybe left away in which case RUSAGE_SELF is used.

The RUSAGE_CHILDREN is the total sum of all the so far terminated (either successfully or unsuccessfully) child processes: there is no way to find out information about child processes still running.

On some systems (those supporting both getrusage() and the POSIX threads) there is also RUSAGE_THREAD. The BSD::Resource supports the RUSAGE_THREAD if it is present but understands nothing more about the POSIX threads themselves.

In list context getrusage() returns the current resource usages as a list. On failure it returns an empty list.

The elements of the list are, in order:

	index	name		meaning usually (quite system dependent)

	 0	utime		user time
	 1	stime		system time
    	 2	maxrss		maximum shared memory
	 3	ixrss		integral shared memory
	 4	idrss		integral unshared data
	 5	isrss		integral unshared stack
	 6	minflt		page reclaims
	 7	majflt		page faults
    	 8	nswap		swaps
	 9	inblock		block input operations
	10	oublock		block output operations
	11	msgsnd		messages sent
	12	msgrcv		messaged received
	13	nsignals	signals received
	14	nvcsw		voluntary context switches
	15	nivcsw		involuntary context switches

In scalar context getrusage() returns the current resource usages as a an object. The object can be queried via methods named exactly like the middle column, name, in the above table.

$ru = getrusage();
print $ru->stime, "\n";

$total_context_switches = $ru->nvcsw + $ru->nivcsw;

For a detailed description about the values returned by getrusage() please consult your usual C programming documentation about getrusage() and also the header file <sys/resource.h>. (In Solaris, this might be <sys/rusage.h>).

Note 1: officially HP-UX does not support getrusage() at all but for the time being, it does seem to.

Note 2: Because not all kernels are BSD and also because of the sloppy support of getrusage() by many vendors many of the values may not be updated. For example Solaris 1 claims in <sys/rusage.h> that the ixrss and the isrss fields are always zero.

getrlimit

($nowsoft, $nowhard) = getrlimit($resource);

$rlimit = getrlimit($resource);

The $resource argument can be one of

	$resource		usual meaning		usual unit

	RLIMIT_CPU		CPU time		seconds

        RLIMIT_FSIZE		file size		bytes

	RLIMIT_DATA		data size		bytes
        RLIMIT_STACK		stack size		bytes
        RLIMIT_CORE		coredump size		bytes
        RLIMIT_RSS		resident set size	bytes
    	RLIMIT_MEMLOCK		memory locked data size	bytes

        RLIMIT_NPROC		number of processes	-

	RLIMIT_NOFILE		number of open files	-
        RLIMIT_OPEN_MAX		number of open files	-

	RLIMIT_AS		(virtual) address space	bytes
        RLIMIT_VMEM		virtual memory (space)	bytes

What limits are available depends on the operating system. See below for get_rlimits() on how to find out which limits are available. The last two pairs (NO_FILE, OPEN_MAX) and (AS, VMEM) are the same, the former being the BSD names and the latter SVR4 names.

Two meta-resource-symbols might exist

RLIM_NLIMITS
RLIM_INFINITY

RLIM_NLIMITS being the number of possible (but not necessarily fully supported) resource limits, see also the get_rlimits() call below. RLIM_INFINITY is useful in setrlimit(), the RLIM_INFINITY is represented as -1.

In list context getrlimit() returns the current soft and hard resource limits as a list. On failure it returns an empty list.

Processes have soft and hard resource limits. On crossing the soft limit they receive a signal (for example the XCPU or XFSZ, corresponding to the RLIMIT_CPU and RLIMIT_FSIZE, respectively). The processes can trap and handle some of these signals, please see "Signals" in perlipc. After the hard limit the processes will be ruthlessly killed by the KILL signal which cannot be caught.

NOTE: the level of 'support' for a resource varies. Not all the systems

a) even recognise all those limits
b) really track the consumption of a resource
c) care (send those signals) if a resource limit get exceeded

Again, please consult your usual C programming documentation.

One notable exception for the better: officially HP-UX does not support getrlimit() at all but for the time being, it does seem to.

In scalar context getrlimit() returns the current soft and hard resource limits as an object. The object can be queried via methods cur and max, the current and maximum resource limits for the $resource, respectively.

getpriority

$nowpriority = getpriority($pr_which, $pr_who);

# the default $pr_who is 0 (the current $pr_which)

$nowpriority = getpriority($pr_which);

# the default $pr_which is PRIO_PROCESS (the process priority)

$nowpriority = getpriority();

getpriority() returns the current priority. NOTE: getpriority() can return zero or negative values completely legally. On failure getpriority() returns undef (and $! is set as usual).

The priorities returned by getpriority() are in the (inclusive) range PRIO_MIN...PRIO_MAX. The $pr_which argument can be any of PRIO_PROCESS (a process) PRIO_USER (a user), or PRIO_PGRP (a process group). The $pr_who argument tells which process/user/process group, 0 signifying the current one.

Usual values for PRIO_MIN, PRIO_MAX, are -20, 20. A negative value means better priority (more impolite process), a positive value means worse priority (more polite process).

NOTE: in AIX if the BSD compatibility library is not installed or not found by the installation procedure of the BSD::Resource the PRIO_MIN is 0 (corresponding to -20) and PRIO_MAX is 39 (corresponding to 19, the BSD priority 20 is unreachable).

setrlimit

$success = setrlimit($resource, $newsoft, $newhard);

setrlimit() returns true on success and undef on failure.

NOTE: A normal user process can only lower its resource limits. Soft or hard limit RLIM_INFINITY means as much as possible, the real hard limits are normally buried inside the kernel and are very system-dependent.

setpriority

$success = setpriority($pr_which, $pr_who, $priority);

# NOTE! If there are two arguments the second one is
# the new $priority (not $pr_who) and the $pr_who is
# defaulted to 0 (the current $pr_which)

$success = setpriority($pr_which, $priority);

# The $pr_who defaults to 0 (the current $pr_which) and
# the $priority defaults to half of the PRIO_MAX, usually
# that amounts to 10 (being a nice $pr_which).

$success = setpriority($pr_which);

# The $pr_which defaults to PRIO_PROCESS, 

$success = setpriority();

setpriority() is used to change the scheduling priority. A positive priority means a more polite process/process group/user; a negative priority means a more impoite process/process group/user. The priorities handled by setpriority() are [PRIO_MIN,PRIO_MAX]. A normal user process can only lower its priority (make it more positive).

NOTE: A successful call returns 1, a failed one 0.

get_rlimits

$rlimits = get_rlimits();

NOTE: This is not a real BSD function. It is a convenience function.

get_rlimits() returns a reference to hash which has the names of the available resource limits as keys and their indices (those which are needed as the first argument to getrlimit() and setrlimit()) as values. For example:

$r = get_rlimits();
print "ok.\n" if ($r->{'RLIM_STACK'} == RLIM_STACK);

EXAMPLES

# the user and system times so far by the process itself

($usertime, $systemtime) = getrusage();

# ditto in OO way

$ru = getrusage();

$usertime   = $ru->utime;
$systemtime = $ru->stime;

# get the current priority level of this process

$currprio = getpriority();

VERSION

Release 1.06, June 1997

AUTHOR

Jarkko Hietaniemi, jhi@iki.fi