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SubjectRE: swap on eMMC and other flash

Great topics. As per one of Rik original points:

> 4) skip writeout of zero-filled pages - this can be a big help
> for KVM virtual machines running Windows, since Windows zeroes
> out free pages; simply discarding a zero-filled page is not
> at all simple in the current VM, where we would have to iterate
> over all the ptes to free the swap entry before being able to
> free the swap cache page (I am not sure how that locking would
> even work)
> with the extra layer of indirection, the locking for this scheme
> can be trivial - either the faulting process gets the old page,
> or it gets a new one, either way it'll be zero filled

Since it's KVMs realm here, can't KSM simply solve the zero-filled pages problem avoiding unnecessary burden for the Swap subsystem?


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