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Our MaxTime and DefaultTime are 14-days. Setting a high DefaultTime was a convenience to our users (and the support team) but has evolved into a mistake because it impacts backfill. Under high load we'll see small backfill jobs take over because the estimated
start and end time of "DefaultTime" jobs are wildly incorrect -- the backfill algorithm is less likely to calculate a delay in larger, highest-priority jobs and backfills smaller jobs. I've tuned many of the backfill SchedulerParameters, but there's no replacement
for an accurate time estimate. <br>
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Default values also become difficult to change once hundreds of submit scripts ignore them. Jason, I think setting a small DefaultTime limit is a good approach. We've considered resetting our default to 1 min to force jobs to specify a time but will (likely)
target an average-ish value now that we have stats from a couple of million jobs.<br>
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- Sebastian<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> slurm-users <slurm-users-bounces@lists.schedmd.com> on behalf of Jason Simms <simmsj@lafayette.edu><br>
<b>Sent:</b> Tuesday, October 6, 2020 7:53 AM<br>
<b>To:</b> Slurm User Community List <slurm-users@lists.schedmd.com><br>
<b>Subject:</b> Re: [slurm-users] Simple free for all cluster</font>
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<div dir="ltr">FWIW, I define the DefaultTime as 5 minutes, which effectively means for any "real" job that users must actually define a time. It helps users get into that habit, because in the absence of a DefaultTime, most will not even bother to think critically
and carefully about what time limit is actually reasonable, which is important for, e.g., effective job backfill and scheduling estimations.<br>
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<div>I currently don't have a MaxTime defined, because how do I know how long a job will take? Most jobs on my cluster require no more than 3-4 days, but in some cases at other campuses, I know that jobs can run for weeks. I suppose even setting a time limit
such as 4 weeks would be overkill, but at least it's not infinite. I'm curious what others use as that value, and how you arrived at it.</div>
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<div>Warmest regards,</div>
<div>Jason</div>
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<div dir="ltr" class="x_gmail_attr">On Tue, Oct 6, 2020 at 5:55 AM John H <<a href="mailto:jsh@sdf.org">jsh@sdf.org</a>> wrote:<br>
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Yes I hadn't considered that! Thanks for the tip, Michael I shall do that.<br>
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John<br>
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On Fri, Oct 02, 2020 at 01:49:44PM +0000, Renfro, Michael wrote:<br>
> Depending on the users who will be on this cluster, I'd probably adjust the partition to have a defined, non-infinite MaxTime, and maybe a lower DefaultTime. Otherwise, it would be very easy for someone to start a job that reserves all cores until the nodes
get rebooted, since all they have to do is submit a job with no explicit time limit (which would then use DefaultTime, which itself has a default value of MaxTime).
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> <br>
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<span style="color:rgb(130,36,51)"><font face="Century Gothic"><b>Jason L. Simms, Ph.D., M.P.H.</b></font></span></div>
<div style="color:rgb(0,0,0); font-family:Helvetica; font-size:14px; margin:0px">
<font face="Century Gothic"><span>Manager of Research and High-Performance Computing</span></font></div>
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<font face="Century Gothic"><span>XSEDE Campus Champion<br>
</span><span style="color:gray">Lafayette College<br>
Information Technology Services<br>
710 Sullivan Rd | Easton, PA 18042<br>
Office: 112 Skillman Library<br>
p: (610) 330-5632</span></font></div>
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