Re: [PATCH] mm:zswap: fix zswap entry reclamation failure in two scenarios

[Chris Li]

On Sun, Nov 19, 2023 at 7:20 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>
> Chris Li <chriscli@xxxxxxxxxx> writes:
>
> > On Thu, Nov 16, 2023 at 12:19 PM Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote:
> > That will cancel the batching effect on the swap slot free, making the
> > common case for  swapping  faults take longer to complete, righ?
> > If I recall correctly, the uncharge is the expensive part of the swap
> > slot free operation.
> > I just want to figure out what we are trading off against. This is not
> > one side wins all situations.
>
> Per my understanding, we don't batch memcg uncharging in
> swap_entry_free() now.  Although it's possible and may improve
> performance.

swap_entry_free() does not do batching, it is at the caller level.

I just checked. The batching is done in free_swap_slot() is still
using swap slot cache and batching.
It uses swapcache_free_entries() to batch free the swap_slots. That is
where the uncharge happens per my understanding.

Chris