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Operating Systems AIX Shared-SMT-4 vs Dedicated-SMT-4 on capped LPAR Post 302968204 by MichaelFelt on Saturday 5th of March 2016 05:23:02 AM
Old 03-05-2016
When running in Dedicated Processor mode - that parition may donate unused cycles to the shared pool. However, when using it's processors CPU1 will always be the exact same physical core, idem for the other three - whatever is assigned when it is activated is what they will be.

When running is Shared Mode only the number of virtual cores is defined. On a system with, e.g., 16 cores activated - while the PHYP will attempt to map virtual to the same physical core (aka Home node) - it is not a requirement - hence the physical core assigned may change (e.g., another LPAR is using it, so rather than wait for it to be free a different core is assigned)

p.s. When donating a core - if a dedicated (processor) partition wants it CPU the borrowing LPAR gets removed immediately by the PHYP.

Hope this explains the basics!
 

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hostinfo(8)						    BSD System Manager's Manual 					       hostinfo(8)

NAME
hostinfo -- host information SYNOPSIS
hostinfo DESCRIPTION
The hostinfo command displays information about the host system on which the command is executing. The output includes a kernel version description, processor configuration data, available physical memory, and various scheduling statistics. OPTIONS
There are no options. DISPLAY
Mach kernel version: The version string compiled into the kernel executing on the host system. Processor Configuration: The maximum possible processors for which the kernel is configured, followed by the number of physical and logical processors avail- able. Note: on Intel architectures, physical processors are referred to as cores, and logical processors are referred to as hardware threads; there may be multiple logical processors per core and multiple cores per processor package. This command does not report the number of processor packages. Processor type: The host's processor type and subtype. Processor active: A list of active processors on the host system. Active processors are members of a processor set and are ready to dispatch threads. On a single processor system, the active processor, is processor 0. Primary memory available: The amount of physical memory that is configured for use on the host system. Default processor set: Displays the number of tasks currently assigned to the host processor set, the number of threads currently assigned to the host proces- sor set, and the number of processors included in the host processor set. Load average: Measures the average number of threads in the run queue. Mach factor: A variant of the load average which measures the processing resources available to a new thread. Mach factor is based on the number of CPUs divided by (1 + the number of runnablethreads) or the number of CPUs minus the number of runnable threads when the number of runnable threads is less than the number of CPUs. The closer the Mach factor value is to zero, the higher the load. On an idle system with a fixed number of active processors, the mach factor will be equal to the number of CPUs. SEE ALSO
sysctl(8) Mac OS X October 30, 2003 Mac OS X
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