Re: KVM architecture docs

Avi Kivity
2008-03-05T05:19:02Z

Zhao Forrest wrote:
>> - swapping allows you to overcommit memory
>>
>
> Normally swapping mechanism choose the Least Recently Used(LRU) pages
> of a process to be swapped out. When KVM uses MMU notifier in linux
> kernel to implement swapping for VM, could KVM choose LRU pages of a
> VM to swap out? If so, could you give a brief description about how
> this is implemented?
>

The Linux memory manager approximates LRU by scanning pages for the
accessed bit, which is set in the pte by the processor when a page is
accessed through that pte. mmu notifiers provide a callback for the
check, so that kvm can check the accessed bit on the shadow ptes.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.