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

[Huang, Ying]

Zhaoyang Huang <huangzhaoyang@xxxxxxxxx> writes:

> On Wed, Apr 19, 2023 at 2:07 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>>
>> "zhaoyang.huang" <zhaoyang.huang@xxxxxxxxxx> writes:
>>
>> > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>> >
>> > It is wasting of effort to reclaim CMA pages if they are not availabe
>> > for current context during direct reclaim. Skip them when under corresponding
>> > circumstance.
>>
>> Do you have any performance number for this change?
> Sorry, No. This patch arised from bellowing OOM issue which is caused
> by MIGRATE_CMA occupying almost 100 percent of zones free pages and
> solved by "168676649 mm,page_alloc,cma: conditionally prefer cma
> pageblocks for movable allocations". This could be a common scenario
> for a zone that has a large proportion of CMA reserved page blocks
> which need to be considered in both allocation and reclaiming
> perspective.

IIUC, your patch is inspired by the OOM issue and the commit 168676649?

Anyway, I think it's better for you to describe the issues you want to
address in the patch description, and show how your patch addresses it
with some tests if possible.  Performance number is just one way to show
it.

Best Regards,
Huang, Ying

> 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
>>
>> Best Regards,
>> Huang, Ying
>>
>> > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>> > ---
>> >  mm/vmscan.c | 11 ++++++++++-
>> >  1 file changed, 10 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/mm/vmscan.c b/mm/vmscan.c
>> > index bd6637f..04424d9 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;
>> > @@ -2239,7 +2245,10 @@ 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 ||
>> > +                     (get_pageblock_migratetype(page) == MIGRATE_CMA && !cma_cap)) {
>> >                       nr_skipped[folio_zonenum(folio)] += nr_pages;
>> >                       move_to = &folios_skipped;
>> >                       goto move;