Re: [Resend PATCHv2] mm: skip CMA pages when they are not available

[Zhaoyang Huang <huangzhaoyang@gmail.com>]

On Sat, May 20, 2023 at 5:58 AM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Fri, 19 May 2023 16:41:41 +0800 Zhaoyang Huang <huangzhaoyang@gmail.com> wrote:
>
> > any comments?
>
> Have any of the regular CMA developers commented on a version of this?
None comments until now. IMO, it is mainly affect reclaiming process.
>
>
> I have a couple of little complaints:
>
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index bd6637f..19fb445 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -2225,10 +2225,16 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
> >         unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
> >         unsigned long skipped = 0;
> >         unsigned long scan, total_scan, nr_pages;
> > +       bool cma_cap = true;
> > +       struct page *page;
> >         LIST_HEAD(folios_skipped);
> >
> >         total_scan = 0;
> >         scan = 0;
> > +       if ((IS_ENABLED(CONFIG_CMA)) && !current_is_kswapd()
> > +               && (gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE))
> > +               cma_cap = false;
> > +
>
> A code comment above this alteration would be good.  Tell the reader
> why we're doing this.
ok, will update
>
>
> >         while (scan < nr_to_scan && !list_empty(src)) {
> >                 struct list_head *move_to = src;
> >                 struct folio *folio;
> > @@ -2239,12 +2245,17 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
> >                 nr_pages = folio_nr_pages(folio);
> >                 total_scan += nr_pages;
> >
> > -               if (folio_zonenum(folio) > sc->reclaim_idx) {
> > +               page = &folio->page;
> > +
> > +               if ((folio_zonenum(folio) > sc->reclaim_idx)
> > +#ifdef CONFIG_CMA
> > +                       || (get_pageblock_migratetype(page) == MIGRATE_CMA && !cma_cap)
> > +#endif
> > +               ) {
> >                         nr_skipped[folio_zonenum(folio)] += nr_pages;
> >                         move_to = &folios_skipped;
> >                         goto move;
> >                 }
>
> That's pretty ugly.  Can we use IS_ENABLED(CONFIG_CMA) here to avoid
> the ifdef?
ok
>