EPT Accessed bit

EPT Accessed bit

[Umesh Deshpande]

Hi,

>From the Intel processor manual I read that accessed bit has been
introduced in EPT. The Redhat 6 release notes mention that "Extended
Page Table age bits enables a host to make smarter choices for
swapping memory under memory pressure".  I couldn't find any related
patches on KVM or LKML. I was wondering if using the EPT accessed bit
requires any support from KVM to allow the host kernel to determine
and swap out the inactive VM pages.

Thanks,
Umesh

Re: EPT Accessed bit

[Wanpeng Li]

Hi Umesh,
On Tue, Aug 12, 2014 at 08:07:48PM -0500, Umesh Deshpande wrote:
>Hi,
>
>>From the Intel processor manual I read that accessed bit has been
>introduced in EPT. The Redhat 6 release notes mention that "Extended
>Page Table age bits enables a host to make smarter choices for
>swapping memory under memory pressure".  I couldn't find any related
>patches on KVM or LKML. I was wondering if using the EPT accessed bit
>requires any support from KVM to allow the host kernel to determine
>and swap out the inactive VM pages.
>

IIUC, host tracks the EPT A bit through mmu notifier.

Regards,
Wanpeng Li 

>Thanks,
>Umesh
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