Re: Path forward for Virtualized Swap?

[Chris Li <chrisl@kernel.org>]

On Tue, Sep 22, 2026 at 5:53 AM Rik van Riel <riel@surriel.com> wrote:
>
> On Tue, 2026-09-22 at 05:43 -1000, Chris Li wrote:
> > On Tue, Sep 22, 2026 at 5:20 AM Gregory Price <gourry@gourry.net>
> > wrote:
> > >
> > > On Tue, Sep 22, 2026 at 03:32:44AM -1000, Chris Li wrote:
> > > > > Right now it has 64GB of memory.
> > > >
> > > > That is exactly my point. You are running 1/8 = 12.5% system ram.
> > > >
> > >
> > > Chris you are missing the point
> > >
> > > Zswap:           8812236 kB
> > > Zswapped:       24927876 kB
> >
> > I am well aware of the point. The 7%-10% data I provided is before
> > compression. After compression, the real saving is about 1.5% - 2%.
> >
> Here I'm at 28% without any issues, with room for
> more.

28% is one thing, 100% is a difference beast completely. If you
haven't tried it, don't assume 100% will behave the same as 28%. There
is a point where too much zswap makes the system unusable. It is hard
to pinpoint the exact upper boundary. However, figuring out the upper
bound larger than that exact boundary is not hard at all. I haven't
seen any one can use 100% system RAM sized memory swap out to zswap.
If you have a data point showing what that system with 100% swap to
zswap looks like, please share it.

>
> > You are not listening. The boundary was set due to feedback from the
> > application SLO. Those are real deployments not imaginary usage.
> > Please respect the user.
> >
> Different users need different things.
>
> The kernel needs to be able to accommodate all of them.
>
> The kernel default should accommodate the people who
> are least capable of configuring their systems.
>
> Hyperscalers can set their own defaults across their
> fleets. They know how to adjust settings.

They can use a safe value, e.g., 100% of RAM. Let the people who know
exactly what they want to swap configure the boundary they want.

Chris