CPUs may have multiple cores and cores may have multiple hardware threads. Cores and threads may share CPU resources with other cores and threads. This makes assessment of CPU capacity difficult.
VMware recommends using the SpecInt (SPEC Integer) benchmark published by SPEC for assessing expected relative CPU performance. SPEC is an organization of computer industry vendors dedicated to developing standardized benchmarks and publishing reviewed results. CPU2006 is the current version of the CPU component benchmark suite from SPEC. The results are broken out by reported metric for:
-
CPU Speed: You can access this benchmark from:
-
CPU Throughput: You can access this benchmark from:
http://www.spec.org/cpu2006/results/rint2006.html
While cint runs one copy of the benchmark, rint runs as many copies as there are threads in the machine.
CPU speed and the number of CPUs available affect performance. You can get a sense of the expected performance by comparing the CPU speed directly to the speed ratings of the CPUs on which the benchmark is based. The current strategy for assessing the number of effective CPUs in a machine is to divide the throughput rating by the speed rating.
For example, a machine with two CPUs and four cores per CPU, with one thread per core, may have a speed rating of 10 and a throughput rating of 40, rather than 80, which would be the expected value if all cores and threads were completely independent. In this case, we say such a machine has 4 effective CPUs.
In general, our software benefits more from faster CPU speed, than the comparable addition of more CPUs. Thus, it is preferred to have 1 CPU rated at 20, than 2 rated at 10.
