[slurm-users] FairShare

[Renfro, Michael]

Yesterday, I posted https://docs.rc.fas.harvard.edu/kb/fairshare/<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.rc.fas.harvard.edu%2Fkb%2Ffairshare%2F&data=04%7C01%7Crenfro%40tntech.edu%7Cc23f89dcb97743ee5eda08d8960679ed%7C66fecaf83dc04d2cb8b8eff0ddea46f0%7C1%7C1%7C637424301864169250%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=%2FnB4ivZeDNrVZiaeupFnAj86oQLOhMu1%2FK6YiuBxTB8%3D&reserved=0> in response to a similar question. If you want the simplest general explanation for FairShare values, it's that they range from 0.0 to 1.0, values above 0.5 indicate that account or user has used less than their share of the resource, and values below 0.5 indicate that that account or user has used more than their share of the resource.

Since all your users have the same RawShares value and are entitled to the same share of the resource, you can see that bdehaven has the most RawUsage and the lowest FairShare value, followed by ajoel and xtsao with almost identical RawUsage and FairShare, and finally ahantau with very little usage and the highest FairShare value.

We use FairShare here as the dominant factor in priorities for queued jobs: if you're a light user, we bump up your priority over heavier users, and your job starts quicker than those for heavier users, assuming all other job attributes are equal.

All these values are relative: in our setup, we'd bump ahantau's pending jobs ahead of the others, and put bdehaven's at the end. But if root needed to run a job outside the sray account, they'd get an enormous bump ahead since the sray account has used far more than its fair share of the resource.

From: slurm-users <slurm-users-bounces at lists.schedmd.com>
Date: Wednesday, December 2, 2020 at 11:23 AM
To: slurm-users at lists.schedmd.com <slurm-users at lists.schedmd.com>
Subject: Re: [slurm-users] FairShare

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I've read the manual and I re-read the other link. What they boil down to is Fair Share is calculated based on a recondite "rooted plane tree", which I do not have the background in discrete math to understand.

I'm hoping someone can explain it so my little kernel can understand.
________________________________
From: slurm-users <slurm-users-bounces at lists.schedmd.com> on behalf of Micheal Krombopulous <MichealKrombopulous at outlook.com>
Sent: Wednesday, December 2, 2020 9:32 AM
To: slurm-users at lists.schedmd.com <slurm-users at lists.schedmd.com>
Subject: [slurm-users] FairShare

Can someone tell me how to calculate fairshare (under fairtree)? I can't figure it out. I would have thought it would be the same score for all users in an account. E.g., here is one of my accounts:

Account     User  RawShares  NormShares    RawUsage   NormUsage  EffectvUsage    LevelFS  FairShare
-------------------- ---------- ---------- ----------- ----------- ----------- ------------- ---------- ----------
root                                               0.000000      611349                  1.000000
 root                      root             1    0.076923           0    0.000000      0.000000        inf   1.000000
 sray                                          1    0.076923      30921 0.505582      0.505582   0.152147
  sray                 phedge            1    0.050000           0    0.000000      0.000000        inf   0.181818
  sray                raab                  1    0.050000           0    0.000000      0.000000        inf   0.181818
  sray                benequist          1    0.050000           0    0.000000      0.000000        inf   0.181818
  sray                 bosch               1    0.050000           0    0.000000      0.000000        inf   0.181818
  sray                rjenkins             1    0.050000           0    0.000000      0.000000        inf   0.181818
  sray                  esmith            1    0.050000           0    0.000000      0.000000 1.7226e+07   0.054545
  sray                  gheinz            1    0.050000           0    0.000000      0.000000 1.9074e+14   0.072727
  sray                  jfitz                 1    0.050000           0    0.000000      0.000000 8.0640e+20   0.081818
  sray                   ajoel              1    0.050000       42449    0.069465      0.137396   0.363913   0.018182
  sray                  jmay               1    0.050000           0    0.000000      0.000000        inf   0.181818
  sray                 aferrier            1    0.050000           0    0.000000      0.000000        inf   0.181818
  sray                bdehaven         1    0.050000      225002    0.367771      0.727420   0.068736   0.009091
  sray                msmythe          1    0.050000           0    0.000000      0.000000        inf   0.181818
  sray                 gfink               1    0.050000           0    0.000000      0.000000 2.0343e+05   0.045455
  sray                ahantau           1    0.050000          31    0.000051      0.000102 491.737549   0.036364
  sray                 hmiller            1    0.050000           0    0.000000      0.000000        inf   0.181818
  sray                   ttinker          1    0.050000           0    0.000000      0.000000 1.4798e+13   0.063636
  sray                wcooper          1    0.050000           0    0.000000      0.000000        inf   0.181818
  sray                 xtsao              1    0.050000       41734    0.068296      0.135083   0.370143   0.027273
  sray                   xping            1    0.050000           0    0.000000      0.000000 1.9833e+24   0.090909

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