Re: cgroup/test_zswap failed with "zswpout does not increase after test program"

[Yosry Ahmed]

On Tue, Jul 7, 2026 at 2:35 PM Nhat Pham <nphamcs@xxxxxxxxx> wrote:
>
> On Tue, Jul 7, 2026 at 11:25 AM Yosry Ahmed <yosry@xxxxxxxxxx> wrote:
> >
> > On Tue, Jul 7, 2026 at 2:38 AM Zenghui Yu <zenghui.yu@xxxxxxxxx> wrote:
> >
> > We were discussing a way for userspace to explicitly trigger a flush
> > before, which would come in handy for testing. However, we decided not
> > to expose flushing as a concept to userspace.
> >
> > Unfortunately I think the only way to "fix" the test is to allocate
> > more memory, enough to trigger a flush on most interesting setups.
> > Perhaps we should scale the amount of memory with the number of CPUs
> > so that we don't have to keep playing whack-a-mole.
>
> I don't have a good idea for writeback, but for zswap out, would
> MADV_PAGEOUT work here?

I don't think the reclaim mechanism is the problem, but the fact that
we don't have enough pending updates to flush the stats. Am I missing
something?