Difference between revisions of "Xen 4.2 Limits"

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#REDIRECT [[Xen_Release_Features]]
{{TODO|This is a work in progress. Feel free to add requests for more to the talk page or add additional information here}}
This document contains information about limits of Xen 4.2.
== CPUs & Memory ==
* Xen can scale up to 4,095 host CPUs with 5Tb of RAM.
* Using Para Virtualization (PV), Xen supports a maximum of 512 VCPUs with 512Gb RAM per guest.
* Using Hardware Virtualization (HVM), Xen supports a maximum of 128 VCPUs with 512Gb RAM per guest.
{{TODO|Should this be 256 for HVM? }}
Note that in theory Xen supports 8192 VCPUs with PV, but event channel limitations (4k per guest) make it impossible for a guest this huge to boot, as each vCPU is expected to minimally require 2 of them (timer vIRQ and IPIs). The guest limits stated above are limits that have been tested. However, it is possibly to exceed these in theory.
== Other Limits ==
* Maximum of 32K interrupts and 2k PCI segments: this limits the number of devices that can be used in two ways:
** The number of devices many can be attached to the system must fit into 2k PCI segments, i.e. 2k * 256 [buses] * 32 [devices] * 8 [functions])
** The number of hardware interrupts they may surface (one would expect at least one interrupt per device function, so this is the stricter of the two limitations).
[[Category:Xen 4.2]]

Latest revision as of 14:19, 16 August 2012