LSF Version 7.3 - Administering Platform LSF

Tuning CPU Factors
96 Administering Platform LSF
bjobs displays hg1 as the execution host instead of hg2:
bjobs
JOBID USER STAT QUEUE FROM_HOST EXEC_HOST JOB_NAME SUBMIT_TIME
520 user1 RUN normal host5 hg1 sleep 1001 Apr 15 13:50
521 user1 RUN normal host5 hg1 sleep 1001 Apr 15 13:50
522 user1 PEND normal host5 sleep 1001 Apr 15 13:51
Importing external host groups (egroup)
When the membership of a host group changes frequently, or when the group
contains a large number of members, you can use an external executable called
egroup to retrieve a list of members rather than having to configure the group
membership manually. You can write a site-specific
egroup executable that
retrieves host group names and the hosts that belong to each group. For
information about how to use the external host and user groups feature, see the
Platform LSF Configuration Reference.
Tuning CPU Factors
CPU factors are used to differentiate the relative speed of different machines. LSF
runs jobs on the best possible machines so that response time is minimized.
To achieve this, it is important that you define correct CPU factors for each
machine model in your cluster.
How CPU factors affect performance
Incorrect CPU factors can reduce performance the following ways.
◆ If the CPU factor for a host is too low, that host may not be selected for job
placement when a slower host is available. This means that jobs would not
always run on the fastest available host.
◆ If the CPU factor is too high, jobs are run on the fast host even when they would
finish sooner on a slower but lightly loaded host. This causes the faster host to
be overused while the slower hosts are underused.
Both of these conditions are somewhat self-correcting. If the CPU factor for a host
is too high, jobs are sent to that host until the CPU load threshold is reached. LSF
then marks that host as busy, and no further jobs will be sent there. If the CPU
factor is too low, jobs may be sent to slower hosts. This increases the load on the
slower hosts, making LSF more likely to schedule future jobs on the faster host.
Guidelines for setting CPU factors
CPU factors should be set based on a benchmark that reflects your workload. If
there is no such benchmark, CPU factors can be set based on raw CPU power.
The CPU factor of the slowest hosts should be set to 1, and faster hosts should be
proportional to the slowest.
Example Consider a cluster with two hosts: hostA and hostB. In this cluster, hostA takes 30
seconds to run a benchmark and
hostB takes 15 seconds to run the same test. The
CPU factor for
hostA should be 1, and the CPU factor of hostB should be 2 because
it is twice as fast as
hostA.