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SubjectRe: Frontswap [PATCH 0/4] (was Transcendent Memory): overview
On 04/30/2010 04:45 AM, Dave Hansen wrote:
>
> A large portion of CMM2's gain came from the fact that you could take
> memory away from guests without _them_ doing any work. If the system is
> experiencing a load spike, you increase load even more by making the
> guests swap. If you can just take some of their memory away, you can
> smooth that spike out. CMM2 and frontswap do that. The guests
> explicitly give up page contents that the hypervisor does not have to
> first consult with the guest before discarding.
>

Frontswap does not do this. Once a page has been frontswapped, the host
is committed to retaining it until the guest releases it. It's really
not very different from a synchronous swap device.

I think cleancache allows the hypervisor to drop pages without the
guest's immediate knowledge, but I'm not sure.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.



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