HP Virtual Server Environment: Tips for Application Developers
ncores=4
#
When run in a vPar with 6 cores:
# ./getnumcores
ncores=6
When run in the same vPar with 6 cores, but configured with 2 FSS Groups (OTHERS and
cputest), a 1 core PSET (pset1) and a 2 core PSET (pset2) here are the results. (The prmrun
command was used to start the executable in each Resource Partition) :
# prmrun -g OTHERS ./getnumcores
ncores=3
# prmrun -g cputest ./getnumcores
ncores=3
# prmrun -g pset1 ./getnumcores
ncores=1
# prmrun -g pset2 ./getnumcores
ncores=2
#
When run on an Integrity VM host with 4 cores:
# ./getnumcores
ncores=4
#
When run on an virtual machine guest with 3 Virtual CPUs on this same Integrity VM host:
# ./getnumcores
ncores=3
Appendix B – Assessing application performance in a VSE
Many applications automatically scale up with increased compute resources, and scale down
gracefully with fewer resources. Some applications are aware of specific physical features of the
system they are running on (CPU count, memory size, etc). For example, as processors shift from
inactive to active states, or vice versa, or processors migrate across partitions, applications that make
assumptions about the number of processors may not take advantage of the additional resources, and
may not deliver the additional performance that the operator expected.
A simple test will confirm that an application scales as expected in a VSE environment:
Set up a performance benchmark with a large amount of static resources. “Large” means
near the upper end of the range that resources might scale to in the production environment.
For example, in an application that may vary from 4 cores to 16 cores in a production
environment, set up a benchmark with 16 cores. “Static” means activate all the resources
before the application begins (no iCAP, no core migration, no WLM, etc). Run the
benchmark and record the performance levels.
Set up the same performance benchmark, start the application with a “small” amount of
resources. In the example above, start with 4 cores. Make this a dynamic environment by
activating the VSE features that will be used in the production environment (iCAP, core
migration, WLM, etc). Increase the load on the application until all the resources have been