On Mon, Sep 25, 2023 at 01:17:04PM -0700, Yosry Ahmed wrote:
> On Tue, Sep 19, 2023 at 10:14 AM Nhat Pham <nphamcs@xxxxxxxxx> wrote:
> > + is_empty = false;
> > + }
> > + zswap_pool_put(pool);
> > +
> > + if (is_empty)
> > + return -EINVAL;
> > + if (shrunk)
> > + return 0;
> > + return -EAGAIN;
> > }
> >
> > static void shrink_worker(struct work_struct *w)
> > {
> > struct zswap_pool *pool = container_of(w, typeof(*pool),
> > shrink_work);
> > - int ret, failures = 0;
> > + int ret, failures = 0, memcg_selection_failures = 0;
> >
> > + /* global reclaim will select cgroup in a round-robin fashion. */
> > do {
> > - ret = zswap_reclaim_entry(pool);
> > + /* previous next_shrink has become a zombie - restart from the top */
>
> Do we skip zombies because all zswap entries are reparented with the objcg?
>
> If yes, why do we restart from the top instead of just skipping them?
> memcgs after a zombie will not be reachable now IIUC.
>
> Also, why explicitly check for zombies instead of having
> shrink_memcg() just skip memcgs with no zswap entries? The logic is
> slightly complicated.
I think this might actually be a leftover from the initial plan to do
partial walks without holding on to a reference to the last scanned
css. Similar to mem_cgroup_iter() does with the reclaim cookie - if a
dead cgroup is encountered and we lose the tree position, restart.
But now the code actually holds a reference, so I agree the zombie
thing should just be removed.
