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Resource(3) User Contributed Perl Documentation Resource(3)
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() with the POSIX threads) there can also be "RUSAGE_THREAD". The
BSD::Resource supports the "RUSAGE_THREAD" if it is present but understands nothing more about the POSIX threads
themselves. Similarly for "RUSAGE_BOTH": some systems support retrieving the sums of the self and child resource
consumptions simultaneously.
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 or current resident set
3 ixrss integral shared memory
4 idrss integral or current unshared data
5 isrss integral or current 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 + $ru->nivcsw;
For a detailed description about the values returned by getrusage() please consult your usual C programming documentation
about getrusage() and also the header file "<sys/resource.h>". (In Solaris, this might be "<sys/rusage.h>").
See also "KNOWN ISSUES".
getrlimit
($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 1
RLIMIT_NOFILE number of open files 1
RLIMIT_OFILE number of open files 1
RLIMIT_OPEN_MAX number of open files 1
RLIMIT_LOCKS number of file locks 1
RLIMIT_AS (virtual) address space bytes
RLIMIT_VMEM virtual memory (space) bytes
RLIMIT_TCACHE maximum number of 1
cached threads
RLIMIT_AIO_MEM maximum memory locked bytes
for POSIX AIO
RLIMIT_AIO_OPS maximum number 1
for POSIX AIO ops
What limits are available depends on the operating system. See below for "get_rlimits()" on how to find out which limits
are available, for the exact documentation consult the documentation of your operatgiing system. The two groups
("NOFILE", C"OFILE", <OPEN_MAX>) and ("AS", "VMEM") are aliases within themselves.
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 often represented as minus
one (-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
"SIGXCPU" or "SIGXFSZ", 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 is 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 limit. On failure it returns "undef".
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).
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.
NOTE: Even the soft limit that is actually set might be lower than what requested for various reasons. One possibility
is that the actual limit on a resource might be controlled by some system variable (e.g. in BSD systems the RLIMIT_NPROC
can be capped by the system variable "maxprocperuid", try "sysctl -a kern.maxprocperuid"), or in many environments core
dumping has been disabled from normal user processes. Another possibility is that a limit is rounded down to some
alignment or granularity, for example the memory limits might be rounded down to the closest 4 kilobyte boundary. In
other words, do not expect to be able to setrlimit() a limit to a value and then be able to read back the same value with
getrlimit().
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.
$success = setpriority();
setpriority() is used to change the scheduling priority. A positive priority means a more polite process/process
group/user; a negative priority means a more impoite process/process group/user. The priorities handled by setpriority()
are ["PRIO_MIN","PRIO_MAX"]. A normal user process can only lower its priority (make it more positive).
NOTE: A successful call returns 1, a failed one 0.
See also "KNOWN ISSUES".
times
use BSD::Resource qw(times);
($user, $system, $child_user, $child_system) = times();
The BSD::Resource module offers a times() implementation that has usually slightly better time granularity than the
times() by Perl core. The time granularity of the latter is usually 1/60 seconds while the former may achieve
submilliseconds.
NOTE: The current implementation uses two getrusage() system calls: one with RUSAGE_SELF and one with RUSAGE_CHILDREN.
Therefore the operation is not `atomic': the times for the children are recorded a little bit later.
NOTE: times() is not imported by default by BSD::Resource. You need to tell that you want to use it.
NOTE: times() is not a "real BSD" function. It is older UNIX.
get_rlimits
use BSD::Resource qw{get_rlimits};
my $limits = get_rlimits();
NOTE: This is not a real BSD function. It is a convenience function introduced by BSD::Resource.
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:
use BSD::Resource qw{get_rlimits};
my $limits = get_rlimits();
for my $name (keys %$limits) {
my ($soft, $hard) = BSD::Resource::getrlimit($limits->{$name});
print "$name soft $soft hard $hard\n";
}
Note that a limit of -1 means unlimited.
ERRORS
o
Your vendor has not defined BSD::Resource macro ...
The code tried to call getrlimit/setrlimit for a resource limit that your operating system vendor/supplier does not
support. Portable code should use get_rlimits() to check which resource limits are defined.
EXAMPLES
# the user and system times so far by the process itself
($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();
KNOWN ISSUES
In AIX (at least version 3, maybe later also releases) if the BSD compatibility library is not installed or not found by
the BSD::Resource installation procedure and when using the getpriority() or setpriority(), the "PRIO_MIN" is 0
(corresponding to -20) and "PRIO_MAX" is 39 (corresponding to 19, the BSD priority 20 is unreachable).
In HP-UX the getrusage() is not Officially Supported at all but for the time being, it does seem to be.
In Mac OS X a normal user cannot raise the RLIM_NPROC over the maxprocperuid limit (the default value is 266, try the
command "sysctl -a kern.maxprocperuid").
In NetBSD RLIMIT_STACK calls fail.
Because not all UNIX kernels are BSD and also because of the sloppy support of getrusage() by many vendors many of the
getrusage() values may not be correctly updated. For example Solaris 1 claims in "<sys/rusage.h>" that the "ixrss" and
the "isrss" fields are always zero. In SunOS 5.5 and 5.6 the getrusage() leaves most of the fiels zero and therefore
getrusage() is not even used, instead of that the /proc interface is used. The mapping is not perfect: the "maxrss"
field is really the current resident size instead of the maximum, the "idrss" is really the current heap size instead of
the integral data, and the "isrss" is really the current stack size instead of the integral stack. The ixrss has no
sensible counterpart at all so it stays zero.
COPYRIGHT AND LICENSE
Copyright 1995-2010 Jarkko Hietaniemi All Rights Reserved
This library is free software; you may redistribute it and/or modify it under the same terms as Perl itself.
AUTHOR
Jarkko Hietaniemi, "jhiATiki.fi"
perl v5.12.0 2010-03-15 Resource(3)
