Comments on: Linux Setting processor affinity for a certain task or process

By: Cyenne

Cyenne — Tue, 07 Feb 2012 08:38:27 +0000

Hi Tony,I have a CentOS 5.7 w/ cPanel 11.30 + ngxcinp plugin. I want to move over to CloudLinux + LiteSpeed. What would you suggest me:a) setup a new server with CentOS 6 -> Install cPanel -> Move customers over -> Upgrade to CloudLinux 6 orb) stay with CentOS 5.7 and upgrade to CloudLinux directly from there?I’ve read that theres no upgrade path between RHEL5 -> RHEL6 and as such nor for CentOS or CloudLinux. Which version do you run on your servers? 5.x or 6.x?Thanks in advance

By: JM

JM — Fri, 05 Aug 2011 13:23:34 +0000

I hawe quad core cpu, and if i want to all linux processes use only 2 cores? What is the right syntax?
Now i have in /etc/init.d/rcS:

/usr/bin/taskset -p 1 1
/usr/bin/taskset -p 1 $$

this sett all proccess to first core, but now i want alocate 2 cores for all proccess

By: Anderson

Anderson — Mon, 27 Jun 2011 13:15:44 +0000

Thanks nixcraft!
Very useful!
Congrats!

By: sobrier

sobrier — Wed, 21 Jul 2010 08:27:44 +0000

Hi,
Could you tell how you change proc affinity, I have found a long time.
Thank you.

By: kannan

kannan — Mon, 09 Nov 2009 09:41:05 +0000

taskset -p option pid
option 1 means 1st processor
option 2 means 2nd processor
option 0xffffffff means all the processor

By: JuanPablo

JuanPablo — Sun, 08 Nov 2009 02:03:32 +0000

how asign a processor to specific user ?

many thanks.

By: chango

chango — Thu, 22 Oct 2009 04:56:43 +0000

I hava a proccess with forks, child process will have the same affinity ??.

Thanks :D

By: mahes

mahes — Tue, 15 Sep 2009 12:03:25 +0000

kool stuff – it helped me a lot .thankx in advance
i am in need of running a application wit the same cofnfig file , but in different processor .
even though i run both pairs in different proccessor (as per ur taskset commands) . both are crashin in the sense if i change something in 1 pair it gets reflected in other..can t they be prevented.

pls help me throu

By: Bernardo B.L.

Bernardo B.L. — Wed, 18 Mar 2009 15:42:42 +0000

Just found the solution
ps -eo psr,pid

this gives the processor in each the pid is current assigned to.

By: Bernardo B.L.

Bernardo B.L. — Wed, 18 Mar 2009 15:29:14 +0000

Nixcraft,

This was a very helpful post. It solved part of my problems. But I still have another problem:
How do I know in each processor a current process is running into.
For instance I have a quadcore machine and want to know if the process with pid 999 is running in the cpu 0, 1, 2 or 3.
top command shows only the processor average utilization by this pid but don’t show each cpu is this.
Taskset let me bound a task to a CPU, but yet i don’t know each cpu this process was previously running into.

thanks

By: Jakob Engblom

Jakob Engblom — Wed, 28 Jan 2009 20:55:34 +0000

What are the key guts needed to make this work? I want to put this into a busybox-based embedded system… where apt-get won’t help me at all. I need to statically get it compiled onto the never-changing initrd…

By: reavers

reavers — Mon, 05 Jan 2009 15:37:12 +0000

How you can unbind a process from the selected processor affinity?
I mean, if you don’t want keep the affinity on a process all time, how can you unbind the established affinity between the processor and the process?
Something like:
taskset -c -p Idprocess?
or
taskset -c * -p Idprocess?
or
taskset -c 0,1,2,3 -p Idprocess?

By: Ankit Singh

Ankit Singh — Mon, 15 Dec 2008 09:06:41 +0000

Ramanath
when you run the command
ankit@hover2:~$ taskset -c -p 0 6369
pid 6369′s current affinity list: 0,1
pid 6369′s new affinity list: 0

0 & 1 is the two cores of my dual core CPU which I changed the affinity to core 0. The above mesg. clearly shows the the affinity was changed to core 0 from core 0,1.

A great article. Keep it up.

Ankit Singh

By: Thiru

Thiru — Fri, 12 Dec 2008 00:46:57 +0000

This is very cool!
One question though: Once you bind a process to certain processors, are those processors dedicated for this process alone? Do other processes use these processors?

By: vivek

vivek — Sat, 08 Nov 2008 16:03:12 +0000

Angelina,

Try following for 2 cpu
taskset -c 0,1 /etc/init.d/oracle-xe start
OR
su - oracle taskset -c 0,1 lsnrctl start taskset -c 0,1 dbstart

OR
taskset -c 0,1 sqlplus '/ as sysdba'
And at SQL prompt type:
startup

HTH

By: Angelina

Angelina — Sat, 08 Nov 2008 14:17:11 +0000

Hi,

How to use task set before the process started?

Example: when I start oracle db, I want to use only 2 CPU2 for oracle DB processes. In this point I do not know what is PID.

Oracle says, if you use 4 CPUs at ANY point of time, you should pay oracle license for 4 CPUs.

Please help me … I do not want to setup kernel maxcpus parameter because I will loose CPUs …I want to use them for some other processes.

Regards,
Angelina

By: franchisu

franchisu — Tue, 29 Jul 2008 14:35:11 +0000

Actually, it evidently works especially when I set a process’ affinity before running the process. I noticed that while running a cpu or memory intensive task such as Virtual box or VMware, alternating/changing processor affinity doesn’t seem as evident as my previous example. Anyone noticed this? Perhaps it has something to do with the Linux kernel overriding the manual affinity changing since the kernel knows how to better handle processes and it probably knows that there will be performance hits when moving processes such as VMware/Virtualbox from one proc to another (e.g. cache hit rate etc) ?

By: anuu

anuu — Tue, 29 Jul 2008 14:19:44 +0000

anu@el[~]$ taskset -c -p 1 11574
pid 11574′s current affinity list: 0,1
pid 11574′s new affinity list: 1

it works to me
debian etch

great tool to look what proceses are running is
htop

By: franchisu

franchisu — Sun, 06 Jul 2008 03:53:41 +0000

hi guys,
I tried using taskset and schedtool interchangeably, and I noticed that when I’m running virtualbox, which is a cpu intensive process, then I change proc affinity which doesn’t seem to have that big an effect in ‘top’. I change from one proc to another and the output of ‘top’ seems unchanged, while the process is already running. However, if I begin a new cpu intensive process and assign it an affinity before running it, then I can see changes in the output of ‘top’. any clues to this? perhaps my already running virtualbox is too ‘attached’ to its original proc that the linux kernel decides to override/not pay attention to my schedtool/taskset commands?

By: InQuest

InQuest — Tue, 06 May 2008 23:07:19 +0000

Does the taskset do its job on already running processes. I tried but it didn’t work. First I ran 2 identical processes without taskset. They were homogeneously running on all 8 cpus I had. Now, when I tried assigning 2 cpus to 1 and 6 to another, it didn’t work.
I killed the process where I assigned 6 cpus. Still the other was using all 8 cpus.