linux-kernel - Re: [PATCH] Multi-gen LRU: skip CMA pages when they are not eligible

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Date:   Wed, 9 Aug 2023 11:09:16 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Charan Teja Kalla <quic_charante@...cinc.com>
Cc:     David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
        zhaoyang.huang@...soc.com, surenb@...gle.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Kalesh Singh <kaleshsingh@...gle.com>
Subject: Re: [PATCH] Multi-gen LRU: skip CMA pages when they are not eligible

On Wed, Aug 9, 2023 at 9:54 AM Kalesh Singh <kaleshsingh@...gle.com> wrote:
>
> On Wed, Aug 9, 2023 at 7:00 AM David Hildenbrand <david@...hat.com> wrote:
> >
> > On 09.08.23 10:05, Charan Teja Kalla wrote:
> > > This patch is based on the commit 5da226dbfce3("mm: skip CMA pages when
> > > they are not available") which skips cma pages reclaim when they are not
> > > eligible for the current allocation context. In mglru, such pages are
> > > added to the tail of the immediate generation to maintain better LRU
> > > order, which is unlike the case of conventional LRU where such pages are
> > > directly added to the head of the LRU list(akin to adding to head of the
> > > youngest generation in mglru).
> > >
> > > No observable issue without this patch on MGLRU, but logically it make
> > > sense to skip the CMA page reclaim when those pages can't be satisfied
> > > for the current allocation context.
> > >
> > > Signed-off-by: Charan Teja Kalla <quic_charante@...cinc.com>
>
> Reviewed-by: Kalesh Singh <kaleshsingh@...gle.com>

Thanks, Charan! Do we need a "Fixes" tag?

> > > ---
> > >   mm/vmscan.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > > index b4329f9..6cbe921 100644
> > > --- a/mm/vmscan.c
> > > +++ b/mm/vmscan.c
> > > @@ -4943,7 +4943,7 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c
> > >       }
> > >
> > >       /* ineligible */
> > > -     if (zone > sc->reclaim_idx) {
> > > +     if (zone > sc->reclaim_idx || skip_cma(folio, sc)) {
> > >               gen = folio_inc_gen(lruvec, folio, false);
> > >               list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]);
> > >               return true;
> >
> > Makes sense to me.