NAME BSD::Process::Affinity - Manipulate CPU affinities on FreeBSD SYNOPSIS use BSD::Process::Affinity qw(:all); cpuset_get_process_mask()->from_num(0x2)->update(); DESCRIPTION Ability to manage CPU affinities from userland was a long-awaited feature in FreeBSD, and it is finally available since 7.1 release. But there's a lack of both documentation and affinity manipulation utilities. In "SEE ALSO" section you'll find links to man pages. First, you should answer to yourself - do you really need such low-level management? Most of the time, answer would be 'no'. Your task must be either really cpu-bounds (not io-bound or network-bound), or you're system administrator and want to restrict users/servies/whatever to be running only on part of all available CPUs. 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. INTERFACE This modules supports functional and object-oriented way to deliver you an Affinity object. You can import any function with cpuset_ prefix into your namespace, or call same function as package method without prefix - result would be the same, an Affinity object. Import can be done using individual names, or all at one once using :all tag. So, the following is the same: use BSD::Process::Affinity qw(cpuset_get_process_mask); cpuset_get_process_mask()->from_num(0x5)->update(); ...and... BSD::Process::Affinity->get_process_mask()->from_num(0x5)->update(); Whenever any error occurs, this module croaks. Get Affinity object All these methods (except for "clone") expects one parameter - an id of object you want to fetch affinity of. You can ommit it - this means 'give data for the current process/thread/whatever'. "cpuset_clone" "clone" Clones current process'es effective set, and makes current process member of just created set. "cpuset_rootof_set" "rootof_set" Gets 'root' set for a given set id. "cpuset_rootof_pid" "rootof_pid" Gets 'root' set for a given process id. "cpuset_current_set" "current_set" Gets set content by given set id. "cpuset_current_pid" "current_pid" Gets effetive set for a given process id. "cpuset_get_thread_mask" "get_thread_mask" Get anonymous mask for a given thread id (not perl's thread id, but a system thread id). "cpuset_get_process_mask" "get_process_mask" Get anonymous mask for a given process id. Processors' mask manipulation These methods can be called only on an already fetched Affinity object. "update" $affinity->update(); Writes back to kernel changes made in set content. Without this call, your changes does not affect anything. "assign" $affinity->assign($pid); Sets set specifiyed in $affinity object as effective set for process $pid. It is an error to apply this method for anonymous masks. "get_cpusetid" $n = $affinity->get_cpusetid(); Returns cpu set internal id - for usage with cpuset_rootof_set/cpuset_current_set. Returns zero for anonymous masks. "to_bits" my $vector = $affinity->to_bits(); Returns "Bit::Vector" object, representing internal state. Then you can perform any actions with that object, and set it back using "from_bits" method. Lowest (rightmost) bit represents CPU0, and so on. "from_bits" $affinity->from_bits($vector); Loads mask represented by $vector into object. Note that you have to call "update" to save changes to kernel, that is not done automatically. Also, see "to_bits" for vector format. This method is chainable with "update". "from_num" my $mask = 0x5; $affinity->from_num($mask); 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 unsigned number, so number of processor it can represent depends on your OS type - 32 or 64 bits. This method is chainable with "update". "SEE ALSO" AUTHOR Sergey Aleynikov LICENSE Copyright (c) 2009 by Sergey Aleynikov. All rights reserved. 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