Re: [PATCH v5 01/11] mm, swap: add virtual swap device infrastructure

[Nhat Pham]

On Mon, Sep 28, 2026 at 2:14 PM Nhat Pham <nphamcs@xxxxxxxxx> wrote:
>
> Vswap does not have that, because vswap is not an ordinary swap
> device. It's implementing the concept of virtualization (the "V" in
> VFS, if you want to make that analogy), made optional to reduce
> overhead when indirection is not needed. That gives you all the
> machinery you need for backend transfer:

... for zswap/compression backend.

It's a necessary condition for non-zswap inter-tier transfer, but not
sufficient. So it's not a solved problem quite there yet (and I don't
know if it can become worth the squeeze, as the data becomes
increasingly colder as you move down the tier).

> layer, where you can update the backend, without having to go and
> chase down all the external references - no PTE walk needed.