[slurm-users] Multifactor fair-share with single account

[Loris Bennett]

Hi Kamil,

Kamil Wilczek <kmwil at mimuw.edu.pl> writes:

> W dniu 4.01.2024 o 07:56, Loris Bennett pisze:
>> Hi Kamil,
>> Kamil Wilczek <kmwil at mimuw.edu.pl> writes:
>> 
>>> Dear All,
>>>
>>> I have a question regarding the fair-share factor of the multifactor
>>> priority algorithm. My current understanding is that the fair-share
>>> makes sure that different *accounts* have a fair share of the
>>> computational power.
>>>
>>> But what if my organisation structure is flat and I have only one
>>> account where all my user reside. Is fair-share algorithm working
>>> in this situation -- does it take into account users (associations)
>>> from this single account, and tries to assing a fair-factor to each
>>> user? Or each user from this account have the same fair-factor at
>>> each iteration?
>>>
>>> And what if I have, say 3 accounts, but I do not wan't to calculate
>>> fair-share between accounts, but between all associations from all
>>> 3 accounts? In other words, is there a fair-share factor for
>>> users/associations instead of accounts?
>>>
>>> Kind regards
>> We have a similar situation.  We do in fact have an account for each
>> research group and the groups are associated with institutes and
>> departments, but we use FairShare=parent so that all users are given the
>> same number of shares and thus treated equally by the fair-share
>> mechanism.
>> 
>
> Hi Loris,
>
> but is the "FairShare=parent" still works for the Fair Tree, which is
> the default algorithm since 19.05? I can find this option only for the
> Classic Fair Share.

We have used this for a long time and when the change from Classic Fair
Share to Fair Tree Fairshare nothing changed for us.

> And I'm trying to differentiate between users, so that they are not
> treated equally by the algorithm. Heavy users should have a lower
> factor.

I am not sure what you mean. Treating users equally and lowering the
priority for heavy users do not contradict each other. 

All our users have the same number of normalised shares, but obviously,
when a user consumes a large amount of resources, this is reflected in
his or her usage and the corresponding fairshare value for the user will
fall and thus so will the priority of his or her future jobs.

> I think I could create an account for each user, but is that a common
> practice and not an overkill?

Because of what I wrote above, I don't think you need this.

> I'm also trying to understand the Fair Tree, because there is a section
> when it says that users can have different factors if their common
> ancestor accounts have different factors. But what if they have only one
> single common ancestor? Would then association/users still be sorted by
> the fair-factor?

We don't use any specific features of Fair Tree Fairshare.  We just have
'parent' all the way down, which results in every user having 1 raw
share, regardless of the total number of users.

HTH

Loris

-- 
Dr. Loris Bennett (Herr/Mr)
FUB-IT (ex-ZEDAT), Freie Universität Berlin