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domain is allowed to access — the numbers x,y and z may be in either decimal

or hexadecimal format.

• Flat Format: Include a list of PCI device addresses of the format:

pci = [’x,y,z’, ...]

where each element in the list is a string specifying the components of the PCI

device address, separated by commas. The components (x, y and z) of the list

may be formatted as either decimal or hexadecimal.

7.4 Scheduler Conﬁguration

Xen offers a boot time choice between multiple schedulers. To select a scheduler, pass

the boot parameter sched=sched name to Xen, substituting the appropriate scheduler

name. Details of the schedulers and their parameters are included below; future ver-

sions of the tools will provide a higher-level interface to these tools.

It is expected that system administrators conﬁgure their system to use the scheduler

most appropriate to their needs. Currently, the BVT scheduler is the recommended

choice.

7.4.1 Borrowed Virtual Time

sched=bvt (the default)

BVT provides proportional fair shares of the CPU time. It has been observed to pe-

nalise domains that block frequently (e.g. I/O intensive domains), but this can be

compensated for by using warping.

Global Parameters

ctx allow the context switch allowance is similar to the ‘quantum’ in traditional sched-

ulers. It is the minimum time that a scheduled domain will be allowed to run

before being pre-empted.

Per-domain parameters

mcuadv the MCU (Minimum Charging Unit) advance determines the proportional

share of the CPU that a domain receives. It is set inversely proportionally to a

domain’s sharing weight.

warp the amount of ‘virtual time’ the domain is allowed to warp backwards

warpl the warp limit is the maximum time a domain can run warped for

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Belkin XM Commander Manuale Utente Pagina 40