Re: [RFC PATCH 0/5] mm, swap: Virtual Swap Space (Swap Table Edition)

[Kairui Song]

On Tue, Jun 2, 2026 at 11:54 PM Nhat Pham <nphamcs@xxxxxxxxx> wrote:
>
> On Mon, Jun 1, 2026 at 10:49 AM Kairui Song <ryncsn@xxxxxxxxx> wrote:
> >
> >
> > That part should be indeed coverable by the si->percpu cluster though, I think.
>
> Yeah agree - we just need to be a bit craftier with it. The
> fundamental problem is in the current model, we're only storing offset
> and si, then look up cluster based on that. But for dynamic vswap,
> that look up takes the xa_load().
>
> Once we move to per-si per-cpu cluster, then I think it becomes ok to
> store the cluster pointer directly, correct?
>
> The reference counting needs to be carefully handled though. I think
> in my old vss design I did something fairly silly - just hold a
> reference to it while it's in cache, then add CPU offlining handler to
> clean up. Not the end of the world I suppose, but maybe there's a
> smarter scheme.

Yeah... I'm not entirely sure about this at this point, maybe it can
be sorted out as we process. Maybe we can also avoid the xa_load with
other techniques too.