Hi Beatrice and Bjørn-Helge,
I can sign, that it works with 18.08.7. We additionally use
TRESBillingWeights together with PriorityFlags=MAX_TRES. For example:
TRESBillingWeights="CPU=1.0,Mem=0.1875G,gres/gpu=12.0"
We use the billing factor for our external accounting. We do this to do
a fair accounting of the nodes. But we do have a similar effect due to
--exclusive.
In Beatrice case, the billingweight would be:
TRESBillingWeights="CPU=1.0,Mem=0.21875G"
So, a 10 cpu job with 1 GB per cpu would be billed 10.
An 1 cpu job with 10 GB would be billed 2 (0.21875*10, floor).
An exclusive 10 cpu job with 1 GB per cpu would be billed 28 (all 28
cores are for the job).
An exclusive 1 cpu job with 30GB (Beatrice' example) would be billed
28(cores)*30(GB)*0.21875 => 118.125 => 118 cores.
Best
Marcus
On 12/12/19 9:47 AM, Bjørn-Helge Mevik wrote:
Beatrice Charton <beatrice.char...@criann.fr> writes:
Hi,
We have a strange behaviour of Slurm after updating from 18.08.7 to
18.08.8, for jobs using --exclusive and --mem-per-cpu.
Our nodes have 128GB of memory, 28 cores.
$ srun --mem-per-cpu=30000 -n 1 --exclusive hostname
=> works in 18.08.7
=> doesn’t work in 18.08.8
I'm actually surprised it _worked_ in 18.08.7. At one time - long before
v 18.08, the behaviour was changed when using --exclusive: In order to
account the job for all cpus on the node, the number of
cpus asked for with --ntasks would simply be multiplied with with
"#cpus-on-node / --ntasks" (so in your case: 28). Unfortunately, that
also means that the memory the job requires per node is "#cpus-on-node /
--ntasks" multiplied with --mem-per-cpu (in your case 28 * 30000 MiB ~=
820 GiB). For this reason, we tend to ban --exclusive on our clusters
(or at least warn about it).
I haven't looked at the code for a long time, so I don't know whether
this is still the current behaviour, but every time I've tested, I've
seen the same problem. I believe I've tested on 19.05 (but I might
remember wrong).
--
Marcus Wagner, Dipl.-Inf.
IT Center
Abteilung: Systeme und Betrieb
RWTH Aachen University
Seffenter Weg 23
52074 Aachen
Tel: +49 241 80-24383
Fax: +49 241 80-624383
wag...@itc.rwth-aachen.de
www.itc.rwth-aachen.de
