Re: [RFC PATCH v2] mm: vmscan: avoid anon scanning for GFP_NOIO with low swapcache in MGLRU

[Baolin Wang]

On 10/23/26 5:19 AM, Barry Song wrote:
> On Thu, Oct 22, 2026 at 7:26 PM Baolin Wang
> <baolin.wang@xxxxxxxxxxxxxxxxx> wrote:
> [...]
>
> > > >                    }
> > > >
> > > >                    if (should_run_aging(lruvec, max_seq, sc, swappiness)) {
> > > > -                       if (try_to_inc_max_seq(lruvec, max_seq,
> > > > swappiness, false))
> > >
> > > This is quite tricky. If we pass swappiness=0, anon aging will be
> > > skipped. Do we want that for GFP_NOIO cases? I mean, these are not
> > > real cases where anon aging should be disabled.
> >
> > No, we have real use cases where 'vm_swappiness' is set to 0, which
> > means the workload never reclaims anon folios. So in this case we don't
> > need to age anon folios.
>
> My concern is that setting swappiness to 0 for GFP_NOIO also skips
> anon aging, making it behave the same as a real swappiness=0.

It will not. We will force anon aging for GFP_NOIO case.

> However, GFP_NOIO is only a temporary state, and subsequent
> allocations may not use GFP_NOIO.