Re: [PATCH v10 0/6] mm/swap, memcg: Introduce swap tiers for cgroup based swap control

[Youngjun Park]

On Mon, Jul 13, 2026 at 08:50:36AM -0700, Yosry Ahmed wrote:
> On Sun, Jul 12, 2026 at 7:57 PM Youngjun Park <youngjun.park@xxxxxxx> wrote:
> >
> > This is the v10 series of the swap tier patchset.
> >
> > v10 folds in the Sashiko review fixes for the selftests added in v9 and
> > rebases onto the current mm-new. There are no functional changes to the
> > core swap or memcg code since v9; see the changelog for details.
> >
> > For context, the bulk of the series is unchanged since v8, with great thanks
> > to Shakeel Butt and Yosry for the reviews and discussions [1] that shaped it.
> > The main change in v8 was the interface change to use memory.swap.tiers.max
> > with '0' (disable) and 'max' (enable) values. This mechanism was suggested
> > by Shakeel and Yosry.
> >
> > This change allows for future extensions to control swap between tiers and
> > aligns better with existing memcg interfaces. It is confined to patch #3's
> > user-facing interface; internally, patch #3 still uses the existing mask
> > processing method, which is implementation-efficient.
> >
> > We also discussed tier extensions. Thanks to Yosry, Nhat and Shakeel for their
> > valuable feedback.
> >
> > Here is a brief summary of our tentative conclusions. Please correct me
> > if anything is misrepresented (details in references):
> >
> > * Zswap tiering [2]:
> >   Zswap can itself be a tier (typically the fastest one). But, until vswap lands,
> >   zswap cannot be the only allowed tier,
> >   since it still needs a physical device for allocation;
> >   that restriction can be lifted once vswap is supported.
> 
> Does this series support zswap being a tier? I cannot find any mention
> of zswap in the patches.

Hello Yosry!

This series does not cover zswap as a tier yet.

My plan is to land the swap tier infrastructure together with the
first use case (cgroup-based swap control) first, and then follow
up with zswap tier support in a subsequent series, continuing the
discussions we've had above. 
(I mentioned on cover letter, right above the overview section)

Does that approach sound reasonable to you?