pistal pistal - 5 days ago 5
Python Question

taskset - python

I have a dual quad core machine. so, the cpu list for me 0-7.

I am trying to run the taskset from python

mapping = [2,2,2,2,2]
for i in range(0,len(mapping)):
cmd = "taskset -c" + str(mapping[r]) + "python <path>/run-apps.py" + thr[r] + "&"
os.system(cmd)


and it says:

taskset: invalid option -- '2'
taskset (util-linux-ng 2.17.2)
usage: taskset [options] [mask | cpu-list] [pid | cmd [args...]]
set or get the affinity of a process

-p, --pid operate on existing given pid
-c, --cpu-list display and specify cpus in list format
-h, --help display this help
-V, --version output version information

The default behavior is to run a new command:
taskset 03 sshd -b 1024
You can retrieve the mask of an existing task:
taskset -p 700
Or set it:
taskset -p 03 700
List format uses a comma-separated list instead of a mask:
taskset -pc 0,3,7-11 700
Ranges in list format can take a stride argument:
e.g. 0-31:2 is equivalent to mask 0x55555555


But the core 2 is available and I am to run the same thing from
commandline
.

taskset -c 2 python <path>/run-apps.py lbm &


not a clue what the issue is..

any hints?

Answer

compared to the commandline you posted, you're missing a couple spaces ... e.g.:

cmd = "taskset -c " +  str(mapping[r]) + " python <path>/run-apps.py " + thr[r] + " &"

In your code, when parsing the "commandline", taskset is seeing the string -c2 which according to many commandline parsing libraries is the same thing as -c -2 which would explain the error that you're seeing.

Sometimes these things are easier to read if you use string interpolation instead:

cmd = "taskset -c %s python <path>/run-apps.py %s &" % (mapping[r],thr[r])

Or new style .format:

cmd = "taskset -c {0} python <path>/run-apps.py {1} &".format(mapping[r],thr[r])

And finally, no solution using os.system should go by without at least a mention of the python subprocess module.

process = subprocess.Popen(['taskset',
                            '-c',
                            str(mapping[r]),
                            'python',
                            '<path>/run-apps.py',
                            str(thr[r]) ] )

It'll avoid the shell altogether which is slightly more efficient and makes you safer from shell injection types of attacks.

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