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Advanced POWER Virtualization on IBM System p5 - Previous ...

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The Hypervisor firmware and the hosted operating systems communicate with<br />

each other through Hypervisor calls (hcalls).<br />

The <str<strong>on</strong>g>POWER</str<strong>on</strong>g> Hypervisor allows multiple instances of operating systems to run <strong>on</strong><br />

<str<strong>on</strong>g>POWER</str<strong>on</strong>g>5 servers c<strong>on</strong>currently. The supported operating systems are listed in<br />

1.4, “Operating system support” <strong>on</strong> page 9.<br />

2.6.1 <str<strong>on</strong>g>POWER</str<strong>on</strong>g> Hypervisor virtual processor dispatch<br />

Shared-processor partiti<strong>on</strong>s are given <strong>on</strong>e or more virtual processors to run their<br />

workload <strong>on</strong>. The number of virtual processors in any partiti<strong>on</strong> and in all<br />

partiti<strong>on</strong>s does not necessarily have any correlati<strong>on</strong> to the number of physical<br />

processors in the shared-processor pool except that each physical processor can<br />

support, at most, ten virtual processors.<br />

The <str<strong>on</strong>g>POWER</str<strong>on</strong>g> Hypervisor manages the distributi<strong>on</strong> of available physical processor<br />

cycles to all the processors in the shared pool. The <str<strong>on</strong>g>POWER</str<strong>on</strong>g> Hypervisor uses a<br />

10 ms dispatch cycle; each virtual processor is guaranteed to get its entitled<br />

share of processor cycles during each 10 ms dispatch window.<br />

To optimize physical processor usage, a virtual processor will yield a physical<br />

processor if it has no work to run or enters a wait-state, such as waiting for a lock<br />

or for I/O to complete. A virtual processor may yield a physical processor through<br />

a Hypervisor call.<br />

Dispatch mechanism<br />

To illustrate the mechanism, c<strong>on</strong>sider three partiti<strong>on</strong>s with two, <strong>on</strong>e, and three<br />

virtual processors. These six virtual processors are mapped to two physical<br />

<str<strong>on</strong>g>POWER</str<strong>on</strong>g>5 cores, as shown in Figure 2-9 <strong>on</strong> page 51.<br />

50 <str<strong>on</strong>g>Advanced</str<strong>on</strong>g> <str<strong>on</strong>g>POWER</str<strong>on</strong>g> <str<strong>on</strong>g>Virtualizati<strong>on</strong></str<strong>on</strong>g> <strong>on</strong> <strong>IBM</strong> <strong>System</strong> <strong>p5</strong>

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