Re: [PATCH v2] mm: add lazyfree folio to lru tail

[Barry Song <21cnbao@gmail.com>]

On Tue, Aug 20, 2024 at 11:54 PM gaoxu <gaoxu2@honor.com> wrote:
>
> >
> > On Fri, Aug 16, 2024 at 7:48 PM gaoxu <gaoxu2@honor.com> wrote:
> > >
> > > Replace lruvec_add_folio with lruvec_add_folio_tail in the lru_lazyfree_fn:
> > > 1. The lazy-free folio is added to the LRU_INACTIVE_FILE list. If it's
> > >    moved to the LRU tail, it allows for faster release lazy-free folio and
> > >    reduces the impact on file refault.
> > > 2. When mglru is enabled, the lazy-free folio is reclaimabled and should be
> > >    added using lru_gen_add_folio(lruvec, folio, true) instead of
> > >    lru_gen_add_folio(lruvec, folio, false) for adding to gen.
> > >
> > > With the change in place, workingset_refault_file is reduced by 33% in
> > > the continuous startup testing of the applications in the Android system.
> > >
> >
> > Hi Gao,
> >
> > Just curious, in which scenario are we frequently calling MADV_FREE but not
> > MADV_DONTNEED?
> Hi Song,
>  Android ART use MADV_FREE, please refer to the following link.
>  https://android-review.googlesource.com/c/platform/art/+/2633132

thanks! It seems like the art guys owe us some changelogs, with
no data and no reason ：-）

Your change seems reasonable to me. Since users plan to free those
anon folios, we should avoid placing them in hard-to-reclaim areas,
which could lead to unnecessarily reclaiming file folios instead.

> >
> > > Signed-off-by: gao xu <gaoxu2@hihonor.com>
> > > ---
> > > V1 -> V2: Based on the latest mm-unstable, recreate the patch.
> > >
> > >  mm/swap.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/mm/swap.c b/mm/swap.c
> > > index 6b838986d..e0dbfc983 100644
> > > --- a/mm/swap.c
> > > +++ b/mm/swap.c
> > > @@ -641,7 +641,7 @@ static void lru_lazyfree(struct lruvec *lruvec, struct
> > folio *folio)
> > >          * anonymous folios
> > >          */
> > >         folio_clear_swapbacked(folio);
> > > -       lruvec_add_folio(lruvec, folio);
> > > +       lruvec_add_folio_tail(lruvec, folio);
> > >
> > >         __count_vm_events(PGLAZYFREE, nr_pages);
> > >         __count_memcg_events(lruvec_memcg(lruvec), PGLAZYFREE,
> > > nr_pages);
> > > --
> > > 2.17.1

Thanks
Barry