Discovery CPU

Multi-threaded CPU seconds for Discoveryand Single-threaded CPU seconds for Discoverycan be used to roughly estimate the discovery time. Discovery must be constrained by Central Processing Unit (CPU), both in the multi- and single-threaded components. The single-threaded components do not overlap each other during discovery. Discovery time can therefore be roughly estimated using the following formula:

Total single-threaded CPU + Total multi-threaded CPU / Number of CPUs

Then, adjust for relative CPU speed from using the Standard Performance Evaluation Corporation (SPEC) rating for the proposed hardware. Appendix A, “Defining a CPU,”provides details on how to adjust the specifications depending upon your hardware.

Discovery will proceed faster with the addition of more and faster CPUs, but additional processing power is not an absolute requirement. There is a limit to the amount of CPU processing power that may be profitably applied for discovery. In the lab environment (with very low network latency) eight discovery threads provided optimal discovery time. It was observed that adding more threads, beyond the optimal number of discovery threads, increases CPU consumption, but does not necessarily improve the discovery time.

More than four CPUs will provide little additional benefit, but this will vary substantially depending on the platform. Sometimes, more than two CPUs for discovery is of little benefit as the amount of parallelism we can achieve varies, making discovery times difficult to predict. The data in Multi-threaded CPU seconds for Discoveryand Single-threaded CPU seconds for Discoverycame from servers running 10 discovery threads. This data reflects the contention from polling and correlation, which normally occurs in discoveries subsequent to the first one. As explained in “Discovery threads” on page 50, the CPU required for additional threads and processors may vary depending on your platform.

Table 1. Multi-threaded CPU seconds for Discovery

Operating system	IP Availability Manager			IP Availability Managerand IP Performance Manager (AM-PM)
	Per interface	Per unmanaged port	Per managed port	Per interface	Per unmanaged port	Per managed port
Linux	0.0320	0.0240	0.2600	0.0400	0.0240	0.3800
Solaris	0.1920	0.1440	1.5600	0.2400	0.1440	2.2800

Table 2. Single-threaded CPU seconds for Discovery

Operating system	IP Availability Manager			IP Availability Managerand IP Performance Manager (AM-PM)
	Per interface	Per unmanaged port	Per managed port	Per interface	Per unmanaged port	Per managed port
Linux	0.0094	0.0036	0.0316	0.0134	0.0040	0.0472
Solaris	0.0563	0.0218	0.1897	0.0803	0.0239	0.2830

Appendix B, “Hardware Specifications,”provides specifications of the servers measured.