Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <1683194994-3070-1-git-send-email-zhaoyang.huang@unisoc.com>
In-Reply-To: <1683194994-3070-1-git-send-email-zhaoyang.huang@unisoc.com>
From:   Zhaoyang Huang <huangzhaoyang@gmail.com>
Date:   Fri, 5 May 2023 16:02:12 +0800
Message-ID: <CAGWkznEqH3b5VbgEa0CFKcZPharKx=wrT0iEea3fGfEoVf0n-A@mail.gmail.com>
Subject: Re: [PATCHv2] mm: optimization on page allocation when CMA enabled
To:     "zhaoyang.huang" <zhaoyang.huang@unisoc.com>, kernel-team@fb.com,
        Qian Cai <cai@lca.pw>, Vlastimil Babka <vbabka@suse.cz>,
        Mel Gorman <mgorman@techsingularity.net>,
        Anshuman Khandual <anshuman.khandual@arm.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <guro@fb.com>,
        Roman Gushchin <roman.gushchin@linux.dev>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, ke.wang@unisoc.com
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

add more reviewer

On Thu, May 4, 2023 at 6:11=E2=80=AFPM zhaoyang.huang <zhaoyang.huang@uniso=
c.com> wrote:
>
> From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
>
> Let us look at the series of scenarios below with WMARK_LOW=3D25MB,WMARK_=
MIN=3D5MB
> (managed pages 1.9GB). We can know that current 'fixed 1/2 ratio' start t=
o use
> CMA since C which actually has caused U&R lower than WMARK_LOW (this shou=
ld be
> deemed as against current memory policy, that is, U&R should either stay =
around
> WATERMARK_LOW when no allocation or do reclaim via enter slowpath)
>
> free_cma/free_pages(MB)      A(12/30)     B(12/25)     C(12/20)
> fixed 1/2 ratio                 N             N           Y
> this commit                     Y             Y           Y
>
> Suggested-by: Roman Gushchin <roman.gushchin@linux.dev>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> ---
> v2: do proportion check when zone_watermark_ok, update commit message
> ---
> ---
>  mm/page_alloc.c | 36 ++++++++++++++++++++++++++++++++----
>  1 file changed, 32 insertions(+), 4 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 0745aed..d0baeab 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3071,6 +3071,34 @@ static bool unreserve_highatomic_pageblock(const s=
truct alloc_context *ac,
>
>  }
>
> +#ifdef CONFIG_CMA
> +static bool __if_use_cma_first(struct zone *zone, unsigned int order, un=
signed int alloc_flags)
> +{
> +       unsigned long cma_proportion =3D 0;
> +       unsigned long cma_free_proportion =3D 0;
> +       unsigned long watermark =3D 0;
> +       long count =3D 0;
> +       bool cma_first =3D false;
> +
> +       watermark =3D wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
> +       /*check if GFP_MOVABLE pass previous watermark check via the help=
 of CMA*/
> +       if (!zone_watermark_ok(zone, order, watermark, 0, alloc_flags & (=
~ALLOC_CMA)))
> +               /* WMARK_LOW failed lead to using cma first, this helps U=
&R stay
> +                * around low when being drained by GFP_MOVABLE
> +                */
> +               cma_first =3D true;
> +       else {
> +               /*check proportion when zone_watermark_ok*/
> +               count =3D atomic_long_read(&zone->managed_pages);
> +               cma_proportion =3D zone->cma_pages * 100 / count;
> +               cma_free_proportion =3D zone_page_state(zone, NR_FREE_CMA=
_PAGES) * 100
> +                       /  zone_page_state(zone, NR_FREE_PAGES);
> +               cma_first =3D (cma_free_proportion >=3D cma_proportion * =
2
> +                               || cma_free_proportion >=3D 50);
> +       }
> +       return cma_first;
> +}
> +#endif
>  /*
>   * Do the hard work of removing an element from the buddy allocator.
>   * Call me with the zone->lock already held.
> @@ -3087,10 +3115,10 @@ static bool unreserve_highatomic_pageblock(const =
struct alloc_context *ac,
>                  * allocating from CMA when over half of the zone's free =
memory
>                  * is in the CMA area.
>                  */
> -               if (alloc_flags & ALLOC_CMA &&
> -                   zone_page_state(zone, NR_FREE_CMA_PAGES) >
> -                   zone_page_state(zone, NR_FREE_PAGES) / 2) {
> -                       page =3D __rmqueue_cma_fallback(zone, order);
> +               if (migratetype =3D=3D MIGRATE_MOVABLE) {
> +                       bool cma_first =3D __if_use_cma_first(zone, order=
, alloc_flags);
> +
> +                       page =3D cma_first ? __rmqueue_cma_fallback(zone,=
 order) : NULL;
>                         if (page)
>                                 return page;
>                 }
> --
> 1.9.1
>