- VERSION INCOMPABILITY
- Get Affinity object
- Processors' mask manipulation
- SEE ALSO
BSD::Process::Affinity - Manipulate CPU affinities on FreeBSD
use BSD::Process::Affinity; BSD::Process::Affinity->get_process_mask()->set(0x2)->update();
Version 0.4 has API partly incompatible with previous releases. Here are differences:
Functional interface is removed, only OO is available now
Lighten API - no more Bit::Vector object manipulations
from_nummethod is renamed to
set, but for one more release is available under it's old name.
Ability to manage CPU affinities from userland was a long-awaited feature in FreeBSD, and it is finally available since 7.1 release. This module allows you to programmatically manipulate them from perl level.
FreeBSD gives you three levels of restricting CPUs for a single process/thread:
'Root' sets - they are set either for a whole system (and containing all processors), or for a jail. You can get root set to see at which processors can your process theoretically run.
Effetive process set - each process is a member of some set (otherwise, it wouldnt't be able run at all, heh). Many processes can be members of a single set, so altering such set - you alter many processes. These sets are only for processes, not for threads - threads can only manipulate with anonymous masks, and has effective set of parent process.
Per-process and per-thread anonymous masks. Each process can get/set it's own (or not own at all) mask, restricting available processors. Manipulating these masks is recommended way in manpages for application developers, when you want to set affinity just for a single process.
Beware, when manipulating affinities, you may degrade performance instead of gaining it.
To operate with this module, you should do three steps:
Fetch an Affinity object for interesting kernel object (either old or new one)
Update it's internal state (or just fetch it)
If required, write changes back to the kernel using
Here is an example that makes current thread NOT to run on 2nd processor in system:
use BSD::Process::Affinity; my $obj = BSD::Process::Affinity->get_thread_mask(); $obj->set($obj->get() & ~0x2)->update();
Note the chainable ability of
Whenever any error occurs, this module croaks.
All these methods (except for
clone) expects one parameter - an id of object you want to fetch affinity of. You can just ommit it - this means 'give data for the current process/thread/whatever'.
Clones current process'es effective set, and makes current process member of just created set.
Gets 'root' set for a given set id.
Gets 'root' set for a given process id.
Gets set content by given set id.
Gets effetive set for a given process id.
Get anonymous mask for a given thread id (not perl's thread id, but a system thread id).
Get anonymous mask for a given process id.
Here are existing Affinity object methods.
Writes back to kernel changes made in set content. Without this call, your changes does not affect anything.
Assigns set specifiyed in $affinity object to be an effective set for process $pid.
It is an error to apply this method to anonymous masks.
my $n = $affinity->get_cpusetid();
Returns cpu set internal id - for usage with rootof_set/current_set. Returns zero for anonymous masks.
my $value = $affinity->get();
Returns usigned integer representing current mask. Then you can perform any actions with it, and set it back using
set method. Lowest (rightmost) bit represents CPU0, and so on.
$affinity->set(0x5); #run on CPU0 and CPU2
Loads mask represented by $mask into object. Note that you have to call
update to save changes to kernel, that is not done automatically.
Mask is treated as an unsigned integer, so number of processor it can represent depends on OS arccitecture - 32 or 64 bits.
This method is chainable with
Sergey Aleynikov <firstname.lastname@example.org>
Copyright (c) 2009, 2011 by Sergey Aleynikov. All rights reserved.
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