Resource(3) User Contributed Perl Documentation Resource(3)NAMEBSD::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.
$success = setpriority();
setpriority() is used to change the scheduling priority. A positive
priority means a more polite process/process group/user; a negative
priority means a more impoite process/process group/user. The
priorities handled by setpriority() are ["PRIO_MIN","PRIO_MAX"]. A
normal user process can only lower its priority (make it more
positive).
NOTE: A successful call returns 1, a failed one 0.
See also "KNOWN ISSUES".
times
use BSD::Resourceqw(times);
($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 $hard\n";
}
Note that a limit of -1 means unlimited.
ERRORS
ยท
Your vendor has not defined BSD::Resource macro ...
The code tried to call getrlimit/setrlimit for a resource limit
that your operating system vendor/supplier does not support.
Portable code should use get_rlimits() to check which resource
limits are defined.
EXAMPLES
# the user and system times so far by the process itself
($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, "jhi@iki.fi"
perl v5.14.2 2010-03-15 Resource(3)
