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TASKSET


Section: Linux User’s Manual (1)
Updated: Apr 2003
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NAME

taskset – retrieve or set a process’s CPU affinity
 

SYNOPSIS

taskset

[optionsmask

command [arg]…


taskset

[options]

-p

[maskpid

 

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 affinity. 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


-p–pid


operate on an existing PID and not launch a new task
-c–cpu-list


specify a numerical list of processors instead of a bitmask. The list may
contain multiple items, separated by comma, and ranges. For example,
0,5,7,9-11.

-h–help


display usage information and exit
-V–version


output 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 must possess
CAP_SYS_NICE

to change the CPU affinity of a process. Any user can retrieve the affinity
mask.
 

AUTHOR

Written by Robert M. Love.
 

COPYRIGHT

Copyright © 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 PARTICULAR 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-ng package and is available from
ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.



 

Index



NAME

SYNOPSIS

DESCRIPTION

OPTIONS

USAGE

PERMISSIONS

AUTHOR

COPYRIGHT

SEE ALSO

AVAILABILITY



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