Re: [PATCH 3/3] mm/zswap: Add per-memcg stat for proactive writeback

[Hao Jia]

On 2026/5/14 05:21, Nhat Pham wrote:
> On Mon, May 11, 2026 at 3:52 AM Hao Jia <jiahao.kernel@xxxxxxxxx> wrote:
> > From: Hao Jia <jiahao1@xxxxxxxxxxx>
> >
> > Currently, zswap writeback can be triggered by either the pool limit
> > being hit or by the proactive writeback mechanism. However, the
> > existing 'zswpwb' metric in memory.stat and /proc/vmstat counts all
> > written back pages, making it difficult to distinguish between pages
> > written back due to the pool limit and those written back proactively.
> >
> > Add a new statistic 'zswpwb_proactive' to memory.stat and /proc/vmstat.
> > This counter tracks the number of pages written back due to proactive
> > writeback. This allows users to better monitor and tune the proactive
> > writeback mechanism.
> >
> > Signed-off-by: Hao Jia <jiahao1@xxxxxxxxxxx>
> > ---
> >   Documentation/admin-guide/cgroup-v2.rst |  4 ++++
> >   include/linux/vm_event_item.h           |  1 +
> >   mm/memcontrol.c                         |  1 +
> >   mm/vmstat.c                             |  1 +
> >   mm/zswap.c                              | 11 +++++++++--
> >   5 files changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
> > index 05b664b3b3e8..29a189b18efc 100644
> > --- a/Documentation/admin-guide/cgroup-v2.rst
> > +++ b/Documentation/admin-guide/cgroup-v2.rst
> > @@ -1734,6 +1734,10 @@ The following nested keys are defined.
> >            zswpwb
> >                  Number of pages written from zswap to swap.
> >
> > +         zswpwb_proactive
> > +               Number of pages written from zswap to swap by proactive
> > +               writeback. This is a subset of zswpwb.
> > +
> >            zswap_incomp
> >                  Number of incompressible pages currently stored in zswap
> >                  without compression. These pages could not be compressed to
>
> nit: once we have reached consensus on an interface, can you add
> documentation for the new knob in cgroup v2 doc and zswap doc too, and
> how it interacts with the other interface (memory.zswap.writeback,
> shrinker_enabled sysfs knob).
>
> A kselftest would be very much appreciated too :)

Thanks, will do in v2

Thanks,
Hao