Changes between Initial Version and Version 1 of WorkFetchMaxConcurrent

Timestamp:

Mar 25, 2019, 9:42:50 PM (5 years ago)

Author:

davea

Comment:

--

WorkFetchMaxConcurrent

@@ +1 @@
+= Work fetch with max concurrent constraints =
+
+current:
+{{{
+rr sim: (pick_jobs_to_run) if project reaches a MC limit,
+        stop picking its jobs
+        (and take it out of the simulation)
+        Need to do this to avoid starvation.
+work fetch: don't fetch from a project at MC limit
+}}}
+
+problem:
+we don't buffer work for projects with MC limits
+
+solution:
+{{{
+rr sim:
+        keep simulating project even if at MC limit
+        keep track of MI(P,R) = max # instances used by MC projects P
+                how many instances the project is able to use, given its MC restriction.
+                It may be all instances.
+        maintain "MC shortfall" MCS(R,P) for each MC project P
+                in update_stats()
+                        y = MI(P,R) - #devices in use by P
+                        x = min(y, nidle)
+                        MCS(R,P) += x*dt
+}}}
+allow work fetch from MC project P,
+        but use MCS(R,P) instead of shortfall; don't request if it's zero
+
+examples (suppose min_buf is 3, max_buf is 6)
+{{{
+4 device instances
+p = project with max concurrent constraint
+x = other projects
+. = idle
+}}}
+example 1:
+P has lots of work, and can use only 2 instances
+{{{
+7       pp..
+6       pp..
+5       pp..
+4       pp..
+3       pp..
+2       pp..
+1       pp..
+}}}
+In this case shortfall is 6,
+but we don't want to request any more work from P
+
+example 2:
+p has limited work.  It can use 1 or 2 instances, depending
+on which app versions run
+{{{
+7       ....
+6       **..
+5       p*..
+4       p*.x
+3       p*xx
+2       pxxx
+1       ppxx
+}}}
+In this case the MC shortfall for P is 5 (the *'s).
+If P had the highest scheduling priority, we'd ask it for 3 units of work.
+After that, it wouldn't be eligible for work fetch because
+the MC shortfall would be zero.
+But we'd be able to ask another project for 4 units.