Changes between Version 54 and Version 55 of cypress/using

Timestamp:

08/21/18 12:29:52 (7 years ago)

Author:

fuji

Comment:

—

cypress/using

@@ -161 +161 @@
 
 This shows that job 2660 allocated close to 40 GB of memory. 
+
+
+==== Job scheduling and priority ====
+
+We would like each of our research groups to have equal opportunity to use the cluster.  Instead of giving each research group a fixed allocation of CPU-time (where the ability to run jobs is cut off after the allocation is reached), SLURM uses a "Fair-share" feature to attempt to give each research group its fair share of resources.  Each job has a priority, which is a number that determines which queued jobs are to be scheduled to run first.
+
+You may use the "sprio" command to see the priority of queued jobs.  For example, the command:
+
+{{{
+sprio -o "%Y %u %i" | sort -nr
+}}}
+
+will return a list of queued jobs in priority order, and 
+{{{
+sprio -j <jobid>
+}}}
+
+(where <jobid> should be replaced by the actual Job ID) will show the components which go into the priority.  These components are:
+
+* Fair-share:  Fair-share is based on historical usage.  For details on SLURM's Fair-share implementation, see here:
+  https://slurm.schedmd.com/priority_multifactor.html#fairshare .
+  In short, the more CPU-time previously used, the lower the priority for subsequent jobs will (temporarily) become.  SLURM has a half-life decay parameter so that more recent usage is weighted more strongly.  We set this half-life on Cypress to 1 week.
+
+* Age:  Jobs that have been waiting in the queue longer get higher priority.
+
+* Job Size:  Larger jobs (i.e. jobs with more CPUs/nodes requested) have higher priority to favor jobs that take advantage of parallel processesing (e.g. MPI jobs).
+
+SLURM calculates each priority component as a fraction (value between 0 and 1), which is then multiplied by a weight.  The current weights are:  Fair-share:  100,000; Age:  10,000;  Job Size:  1,000.  That is, Fair-share is the major contributor to priority.  The weighted components are added to give the final priority.
 
 === MPI Jobs ===