Re: System Panic Makes My Life Easier

On Thu, Jul 28, 2016 at 5:14 PM, Steve Litt <[email protected]>
wrote:

> On Thu, 28 Jul 2016 20:58:25 +0000 (UTC)
> Daniel Gimpelevich <daniel-R/[email protected]> wrote:
>
> > On Thu, 28 Jul 2016 13:34:59 -0400, Steve Litt wrote:
> > > My prime number generator hits the processor and RAM hard, and also
> > > exercises the hard disk. It's pretty easy to compile and run it on a
> > > live CD:
> > >
> > > http://www.troubleshooters.com/codecorn/primenumbers/
> > primenumbers.htm#_Implementation:_Scalability_Through_Paging
> > >
> > > If you run my prime number generator, watch your processor
> > > temperature like a hawk.
> >
> > It may have hit the processor hard in a desirable way when you wrote
> > it, but today, SMP is the norm, and the code above is
> > single-threaded, and due to its other resource usage, you can't just
> > run multiple instances.
>
> What if I run four of them, and three of them are piped to /dev/null?


You can use taskset to pin a process to a given cpu. Here is a simple
example:

# ./foo.sh  & ./foo.sh & ./foo.sh & ./foo.sh &
[1] 28840
[2] 28841
[3] 28842
[4] 28843
[root@ip-172-16-6-116 ~]# taskset -c 0 -p 28840
taskset: failed to execute -p: No such file or directory
[root@ip-172-16-6-116 ~]# taskset -p -c 0 28840
pid 28840's current affinity list: 0-15
pid 28840's new affinity list: 0
[root@ip-172-16-6-116 ~]# taskset -p -c 1 28841
pid 28841's current affinity list: 0-15
pid 28841's new affinity list: 1
[root@ip-172-16-6-116 ~]# taskset -p -c 2 28842
pid 28842's current affinity list: 0-15
pid 28842's new affinity list: 2
[root@ip-172-16-6-116 ~]# taskset -p -c 3 28843
pid 28843's current affinity list: 0-15
pid 28843's new affinity list: 3

Using top you can see that the four processes are running on CPUs 0-3:

# top -bn1 | grep foo.sh
 28840 root      20   0  110m 2972 2776 S  0.0  0.0   0:00.03  0 foo.sh
 28841 root      20   0  110m 2928 2728 S  0.0  0.0   0:00.03  1 foo.sh
 28842 root      20   0  110m 2956 2760 S  0.0  0.0   0:00.03  2 foo.sh
 28843 root      20   0  110m 2932 2736 S  0.0  0.0   0:00.03  3 foo.sh

David Colon
[email protected]
https://tech.dcolon.org

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