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

[Zhaoyang Huang]

This patch could be more helpful when large cma reserved areas reside
in a single zone(etc. 500MB among a 2GB zone), where a lot of CMA
pages spread in LRU allocated by fallback of GFP_MOVABLE allocation.

On Thu, Apr 20, 2023 at 4:33 PM zhaoyang.huang
<zhaoyang.huang@xxxxxxxxxx> wrote:
>
> From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>
> This patch fixes unproductive reclaiming of CMA pages by skipping them when they
> are not available for current context. It is arise from bellowing OOM issue, which
> caused by large proportion of MIGRATE_CMA pages among free pages. There has been
> commit(168676649) to fix it by trying CMA pages first instead of fallback in
> rmqueue. I would like to propose another one from reclaiming perspective.
>
> 04166 < 4> [   36.172486] [03-19 10:05:52.172] ActivityManager: page allocation failure: order:0, mode:0xc00(GFP_NOIO), nodemask=(null),cpuset=foreground,mems_allowed=0
> 0419C < 4> [   36.189447] [03-19 10:05:52.189] DMA32: 0*4kB 447*8kB (C) 217*16kB (C) 124*32kB (C) 136*64kB (C) 70*128kB (C) 22*256kB (C) 3*512kB (C) 0*1024kB 0*2048kB 0*4096kB = 35848kB
> 0419D < 4> [   36.193125] [03-19 10:05:52.193] Normal: 231*4kB (UMEH) 49*8kB (MEH) 14*16kB (H) 13*32kB (H) 8*64kB (H) 2*128kB (H) 0*256kB 1*512kB (H) 0*1024kB 0*2048kB 0*4096kB = 3236kB
>         ......
> 041EA < 4> [   36.234447] [03-19 10:05:52.234] SLUB: Unable to allocate memory on node -1, gfp=0xa20(GFP_ATOMIC)
> 041EB < 4> [   36.234455] [03-19 10:05:52.234] cache: ext4_io_end, object size: 64, buffer size: 64, default order: 0, min order: 0
> 041EC < 4> [   36.234459] [03-19 10:05:52.234] node 0: slabs: 53,objs: 3392, free: 0
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> ---
> v2: update commit message and fix build error when CONFIG_CMA is not set
> ---
> ---
>  mm/vmscan.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
>
> 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;
> +
>         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;
>                 }
> -
>                 /*
>                  * Do not count skipped folios because that makes the function
>                  * return with no isolated folios if the LRU mostly contains
> --
> 1.9.1
>