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Special Forums News, Links, Events and Announcements Software Releases - RSS News Portable Linux Processor Affinity 1.1 (Default branch)
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Old 02-22-2008
Portable Linux Processor Affinity 1.1 (Default branch)
PLPA is an attempt to solve the problem ofmultiple API's for processor affinity withinLinux. Specifically, the functionssched_setaffinity() and sched_getaffinity() havenumbers and types of parameters depending on yourLinux vendor and/or version of GLibc. This isquite problematic for applications attempting touse processor affinity in Linux for compile-time,link-time, and run-time reasons. The PLPA providesa single processor affinity API that developerscan write to in order to get both consistentbehavior and binary compatibility across differentLinux installations (assuming that you have anexecutable that is otherwise binary Linux portable).License: BSD License (revised)Changes:
The ability to understand (socket,core) tuples forspecific process placement was added, as opposedto just specifying Linux virtual processor IDs.The plpa-taskset executable was also added, whichunderstands the same command line syntax as the"taskset" command, but also understands(core@socket) nomenclature.Image

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LEARN ABOUT CENTOS

taskset

TASKSET(1)							   User Commands							TASKSET(1)

NAME

       taskset - retrieve or set a process's CPU affinity

SYNOPSIS

       taskset [options] mask command [arg]...
       taskset [options] -p [mask] pid

DESCRIPTION

       taskset	is  used to set or retrieve the CPU affinity of a running process given its PID or to launch a new COMMAND with a given CPU affin-
       ity.  CPU affinity is a scheduler property that "bonds" a process to a given set of CPUs on the system.	The Linux scheduler will honor the
       given  CPU  affinity and the process will not run on any other CPUs.  Note that the Linux scheduler also supports natural CPU affinity: the
       scheduler attempts to keep processes on the same CPU as long as practical for performance  reasons.   Therefore,  forcing  a  specific  CPU
       affinity is useful only in certain applications.

       The  CPU  affinity  is represented as a bitmask, with the lowest order bit corresponding to the first logical CPU and the highest order bit
       corresponding to the last logical CPU.  Not all CPUs may exist on a given system but a mask may specify more  CPUs  than  are  present.	 A
       retrieved  mask	will  reflect only the bits that correspond to CPUs physically on the system.  If an invalid mask is given (i.e., one that
       corresponds to no valid CPUs on the current system) an error is returned.  The masks are typically given in hexadecimal.  For example,

       0x00000001
	      is processor #0

       0x00000003
	      is processors #0 and #1

       0xFFFFFFFF
	      is all processors (#0 through #31).

       When taskset returns, it is guaranteed that the given program has been scheduled to a legal CPU.

OPTIONS

       -a, --all-tasks
	      Set or retrieve the CPU affinity of all the tasks (threads) for a given PID.

       -p, --pid
	      Operate on an existing PID and do not launch a new task.

       -c, --cpu-list
	      Specify a numerical list of processors instead of a bitmask.  The numbers are separated by commas and may include ranges.  For exam-
	      ple: 0,5,7,9-11.

       -h, --help
	      Display usage information and exit.

       -V, --version
	      Display version information and exit.

USAGE

       The default behavior is to run a new command with a given affinity mask:
	      taskset mask command [arguments]

       You can also retrieve the CPU affinity of an existing task:
	      taskset -p pid

       Or set it:
	      taskset -p mask pid

PERMISSIONS

       A user can change the CPU affinity of a process belonging to the same user.  A user must possess CAP_SYS_NICE to change the CPU affinity of
       a process belonging to another user.  A user can retrieve the affinity mask of any process.

AUTHOR

       Written by Robert M. Love.

COPYRIGHT

       Copyright (C) 2004 Robert M. Love
       This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
       LAR PURPOSE.

SEE ALSO

       chrt(1), nice(1), renice(1), sched_setaffinity(2), sched_getaffinity(2)

       See sched_setscheduler(2) for a description of the Linux scheduling scheme.

AVAILABILITY

       The taskset command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux							    April 2003								TASKSET(1)