How to limit users to N cores?

Question

I have an SSH server where users login to do various tasks. The problem is I have 4 cores, and one user is running tasks on 4. How can I limit the number of cores any given user can use?

This is not a virtual machine.

UPDATE: I was reading /etc/security/limits.conf and saw

#*               soft    core            0
#root            hard    core            100000
#*               hard    rss             10000
#@student        hard    nproc           20
#@faculty        soft    nproc           20
#@faculty        hard    nproc           50
#ftp             hard    nproc           0
#ftp             -       chroot          /ftp
#@student        -       maxlogins       4

I tried setting this up so that a user is limited to 3 processes. but the user gets

 -bash: fork: retry: No child processes

in their terminal.

I have started looking into ulimit, and quota

score 1 · Accepted Answer · edited Feb 09 '14 at 16:13

1

taskset(1) may help you. It can set the core number for one process. You can use ps(1) to get all the process of target user. For example,

housezet@arch: ~
$ ps aux | awk '/^housezet/{print $2}' | xargs -l taskset -p 0x00000001

This wil limit housezet's current process only use one core. And if limiting cpu usage is also acceptable, you can also consider using cpulimit(1).

edited Feb 09 '14 at 16:13

Avinash Raj

78,556

answered Feb 09 '14 at 01:33

House Zet

457
3
8

I am going back and forth with this solution. How would I set this to run when the user logs in? – j0h Feb 10 '14 at 00:58
1

@j0h For systemwide, create a service under /etc/systemd/system/multi-user.target.wants/ or startup script under /etc/init.d/ with something like watch(1) to repeat this command. Putting script under /etc/profile.d/ will make it works when user logs in. You can look at here for more about autostarting. – House Zet Feb 10 '14 at 01:15
If a have 8 cores and do this for 2 users limiting to 4 cores each. would it mean that when they run the desktop (mate ) and chrome in mate, that chrome could use between 1 and 4 cores per user? That's what I want to do. They would log in via vnc. – ycomp Jul 10 '17 at 19:54

score 0 · Answer 2 · answered Feb 09 '14 at 01:10

I don't believe there is any existing tool that would handle what you're after, as it's not a particularly easy thing to do. Handling of which process goes where isn't done in userspace.

The only way I can think of to kind of do what you're after is to use ulimit to set the maximum amount of CPU time, which would prevent a user from hogging everything too much. You can also change a user's nice level, so if a particular user is slamming the CPU you can lower their prority.

How to limit users to N cores?

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