LSF Version 7.3 - Using Platform LSF HPC

CPU radius and processor topology
If LSB_CPUSET_BESTCPUS is set in lsf.conf, LSF can choose the best set of
CPUs that can create a cpuset. The best cpuset is the one with the smallest CPU radius
that meets the CPU requirements of the job. CPU radius is determined by the processor
topology of the system and is expressed in terms of the number of router hops between
CPUs.
For better performance, CPUs connected by metarouters are given a relatively high
weights so that they are the last to be allocated
Best-fit and first-fit CPU list
By default, LSB_CPUSET_BESTCPUS=Y is set in lsf.conf. LSF applies a best-fit
algorithm to select the best CPUs available for the cpuset.
For example, the following command creates an exclusive cpuset with the 8 best CPUs
if available:
bsub -n 8 -extsched "CPUSET[CPUSET_OPTIONS=CPUSET_CPU_EXCLUSIVE]" myjob
If LSB_CPUSET_BESTCPUS is not set in lsf.conf, LSF builds a CPU list on a first-
fit basis; in this example, the first 8 available CPUs are used.
Maximum radius for dynamic cpusets
Use the MAX_RADIUS cpuset external scheduler option to specify the maximum
radius for dynamic cpuset allocation. If LSF cannot allocate a cpuset with radius less
than or equal to MAX_RADIUS, the job remains pending.
MAX_RADIUS implies that the job cannot span multiple hosts. Platform LSF puts each
cpuset host into its own group to enforce this when MAX_RADIUS is specified.
How the best CPUs are selected
Allocating cpusets on multiple hosts (Altix only)
On SGI Altix systems, if a single host cannot satisfy the cpuset requirements for the job,
LSF will try to allocate cpusets on multiple hosts, and the parallel job will be launched
within the cpuset.
specified specified or
not specified
N first fit cpus in
CPU_LIST
not
specified
specified or
not specified
N first fit all cpus in
system
specified specified Y max radius cpus in
CPU_LIST
not
specified
specified Y max radius all cpus in
system
specified not specified Y best fit cpus in
CPU_LIST
not
specified
not specified Y best fit all cpus in
system