Administering Platform LSF - SAS

Performance Tuning for Interactive Batch Jobs
is in use, and resume after the host has been idle for a longer period. For hosts
where all batch jobs, no matter how important, should be suspended, set a perhost
suspending threshold in the lsb.hosts file.
CPU run queue
length (r15s, r1m,
r15m)
CPU utilization
(ut)
Running more than one CPU-bound process on a machine (or more than one
process per CPU for multiprocessors) can reduce the total throughput because
of operating system overhead, as well as interfering with interactive users.
Some tasks such as compiling can create more than one CPU-intensive task.
Queues should normally set CPU run queue scheduling thresholds below 1.0,
so that hosts already running compute-bound jobs are left alone. LSF scales the
run queue thresholds for multiprocessor hosts by using the effective run queue
lengths, so multiprocessors automatically run one job per processor in this
case.
For concept of effective run queue lengths, see lsfintro(1).
For short to medium-length jobs, the r1m index should be used. For longer
jobs, you might want to add an r15m threshold. An exception to this are high
priority queues, where turnaround time is more important than total
throughput. For high priority queues, an r1m scheduling threshold of 2.0 is
appropriate.
The ut parameter measures the amount of CPU time being used. When all the
CPU time on a host is in use, there is little to gain from sending another job to
that host unless the host is much more powerful than others on the network.
A ut threshold of 90% prevents jobs from going to a host where the CPU does
not have spare processing cycles.
If a host has very high pg but low ut, then it may be desirable to suspend some
jobs to reduce the contention.
Some commands report ut percentage as a number from 0-100, some report it
as a decimal number between 0-1. The configuration parameter in the
lsf.cluster.cluster_name file and the configuration files take a fraction in
the range from 0 to 1, while the bsub -R resource requirement string takes an
integer from 1-100.
The command bhist shows the execution history of batch jobs, including the
time spent waiting in queues or suspended because of system load.
The command bjobs -p shows why a job is pending.
Scheduling conditions and resource thresholds
Three parameters, RES_REQ, STOP_COND and RESUME_COND, can be
specified in the definition of a queue. Scheduling conditions are a more
general way for specifying job dispatching conditions at the queue level. These
parameters take resource requirement strings as values which allows you to
specify conditions in a more flexible manner than using the loadSched or
loadStop thresholds.
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Administering Platform LSF