===================================================================
--- branches/boinc_core_release_6_10/checkin_notes 2010-01-14
21:37:15 UTC (rev 20165)
+++ branches/boinc_core_release_6_10/checkin_notes 2010-01-14
21:40:31 UTC (rev 20166)
@@ -188,3 +188,26 @@
client/
scheduler_op.cpp
work_fetch.cpp
+
+David 5 Jan 2010
+ - client: scheduling problem:
+ - a project overestimates job FLOP counts
+ - the client starts jobs in EDF mode
+ - as job progresses and fraction done increases,
+ its completion time estimate decreases until
+ it's no longer a deadline miss.
+ - job gets preempted by other job from that project;
+ you end up with lots of partly completed jobs.
+ Solution (I hope): if an app version has running jobs,
+ compute a "temp DCF" for the app version,
+ which is the min of dynamic/static estimates for its jobs.
+ Apply this scaling factor to completion time estimates
+ for unstarted jobs in RR simulation
+ - client: the estimation of remaining time of running jobs was wrong
+ (how did this bug survive so long?)
+
+ client/
+ app.h
+ client_types.h
+ rr_sim.cpp
+ work_fetch.cpp
The problem described is not the actual problem. The basic problem can
happen even if the estimate is exact.
The real problem is that a task when running may be using CPU time faster
than its resource fraction. This is true if the resource fraction for the
project < number of CPUs for the task / ncpus. In this case, at some point
during the run of the task, the task will no longer be in deadline trouble.
If there are other tasks in deadline trouble with later deadlines, these
tasks will instantly preempt the running task.
The fix for this is an EDF simulation that has the ability to turn off
preemption. The fix checked in will have no effect on this problem.
jm7
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