OT: renice jobs running for more than 5 minutes

[Ranjan Maitra]

On Mon, 22 Feb 2016 10:58:53 -0800 Rick Stevens <ricks at alldigital.com> wrote:

> On 02/22/2016 10:50 AM, Ranjan Maitra wrote:
> > On Mon, 22 Feb 2016 10:38:30 -0800 Rick Stevens <ricks at alldigital.com> wrote:
> >
> >> On 02/22/2016 10:19 AM, Ranjan Maitra wrote:
> >>> Hi,
> >>>
> >>> I am running a fully updated F23 box but this question does not have much to do with Fedora itself, hence the designator and the disclaimer.
> >>>
> >>> I am wanting to run a script which will look at all the jobs that are running and renice all of them which have been on for more than five minutes. (Then I can run the script as a cron job as root and be done with automating the process.)
> >>>
> >>> Are there any suggestions as to how to go about this task efficiently? Actually, before I reinvent the wheel, are there any standard options that already exist and which would be more suitable for me than just to do everything from scratch.
> >>
> >> Use the "-o pid,etimes=" options of ps to get the elapsed time of
> >> tasks in seconds. To get a full list, for example, as root:
> >>
> >> 	ps ax -o pid,uid,etimes=
> >> 	...
> >> 	21412     0     833
> >> 	21499     0  631433
> >> 	21541     0     773
> >> 	21597  1000     769
> >> 	21604  1000     769
> >> 	21605  1000     769
> >> 	21608  1000     769
> >> 	21610  1000     769
> >> 	21613  1000     769
> >> 	21681  1000     769
> >> 	21686  1000     769
> >> 	21697  1000     769
> >> 	21751  1000     742
> >> 	...
> >>
> >> (run it as root so you can see ALL of the processes)
> >>
> >> As you can see, you get three columns: the first is the PID of the
> >> task, the second is the EUID of the user running it, and the third is
> >> the elapsed time.
> >>
> >> So, pull that data into a shell array, look for stuff that has the
> >> second column equal to the user ID you're interested in and the third
> >> column >= 300 seconds and renice the PID in the first column. Note that
> >> I'd avoid renicing any tasks with UIDs < your lowest normal user ID
> >> (typically 100) to keep from starving system tasks.
> >>
> >> Hope that helps!
> >
> > Yes, this absolutely helps, thanks!! But is there a 2-d array in bash (or do we do array of arrays)? (I am presuming that I need to store this in a 2-d array and then look at columns 2 and 3  and renice the PIDs in column 1.) Also, how does one assign the output of the ps to a 2-d array?
> 
> Uhm, no. You can simulate them using associative arrays, but it gets
> rather hairy. You may want to try something like awk or PHP or Perl to
> do this more easily.

OK, thanks! I guess i will have to figure out one of awk, etc then. Separately, I have realized that I should also output nice as part of the ps options because there is no point in renicing jobs that are already niced.

Best wishes,
Ranjan

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