CPU assignment bash script Post: 302422956

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Top Forums Shell Programming and Scripting CPU assignment bash script Post 302422956 by mcky on Wednesday 19th of May 2010 09:50:57 PM

05-19-2010

Registered User

CPU assignment bash script

Hi guys,

I'm basically looking for some help with a bash script I've written. It's purpose is to assign process to individual CPU cores once that process hits 15% CPU usage or more. If it drops below 15%, it's unassigned again (using taskset).

My problem is that I can't think of a way to make the script check if the process is already assigned to an invidividual core, and if so to make it skip the assigning process and remove that core from the array of available cores (there is only enough cores in the array to allow each core to have two processes assigned each [there won't be more than that many processes on the machine so it won't ever go over the limit]). As it currently works, a process might be over 15% and already assigned to one CPU, but if another process' status has changed it could be moved from one CPU to another. I'd like this not to happen, so it doesn't switch processes between CPUs all the time.

Keep in mind I'm pretty basic in my knowledge of this stuff so some parts of the script might be a bit iffy as well. Any suggestions to fix other parts would be appreciated too.

This is what I have so far (for a quad core [you can see it's only for processes with ds_i in them]):

Code:

CPUS=( 1 2 3 0 1 2 3 0 )

PIDS=( `top -b -n 1 | grep ds_i | egrep '[SDR]   ( [0-9]|1[1-4]) ' | sed -e "s/^ *//" -e "s/ .*$//"` )

# Processes with 14% or less usage
for (( e = 0 ; e < ${#PIDS[@]} ; e++ ))
do
taskset -cp 0-3 ${PIDS[$e]}
chrt -o -p 0 ${PIDS[$e]}
done

unset PIDS


PIDS=( `top -b -n 1 | grep ds_i | egrep '[SDR]   ([1][5-9]|[2-9][0-9]) ' | sed -e "s/^ *//" -e "s/ .*$//"` )
# Processes with 15%+ CPU usage
for (( p = 0 ; p < ${#PIDS[@]} ; p++ ))
do
AFF=`taskset -cp ${PIDS[$p]} | sed -e "s/.* current affinity list: //"`

len=`echo $AFF | wc -c`
len=`expr $len - 1`

if [ $len -lt "2" ]
then

        if [ $AFF -lt "4" ]
        then
                for (( e = 0 ; e < ${#CPUS[@]} ; e++ ))
                do

                        if [[ $AFF == ${CPUS[$e]} ]]
                        then
                        unset CPUS[$e] #Remove used CPU from array
                        CPUS=( ${CPUS[*]} )
                        unset PIDS[$p] #Remove PID from array
                        break
                        fi
                done
        fi
fi
done

PIDS=( ${PIDS[*]} )

for (( p = 0 ; p < ${#PIDS[@]} ; p++ ))
do

taskset -cp ${CPUS[0]} ${PIDS[$p]}
chrt -f -p 59 ${PIDS[$p]}
unset CPUS[0]
CPUS=( ${CPUS[*]} )

done

mcky

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LEARN ABOUT OPENDARWIN

taskset

TASKSET(1)							   User Commands							TASKSET(1)

NAME

       taskset - set or retrieve a process's CPU affinity

SYNOPSIS

       taskset [options] mask command [argument...]
       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 may be specified in hexadecimal  (with  or	without  a
       leading "0x"), or as a CPU list with the --cpu-list option.  For example,

	   0x00000001  is processor #0,

	   0x00000003  is processors #0 and #1,

	   0xFFFFFFFF  is processors #0 through #31,

	   32	       is processors #1, #4, and #5,

	   --cpu-list 0-2,6
		       is processors #0, #1, #2, and #6.

       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.

       -c, --cpu-list
	      Interpret  mask  as numerical list of processors instead of a bitmask.  Numbers are separated by commas and may include ranges.  For
	      example: 0,5,8-11.

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

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

       -h, --help
	      Display help text 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.

SEE ALSO

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

       See sched(7) for a description of the Linux scheduling scheme.

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 MER-
       CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

AVAILABILITY

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

util-linux							    August 2014 							TASKSET(1)