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

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Date:   Wed, 9 Aug 2023 16:00:28 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Charan Teja Kalla <quic_charante@...cinc.com>,
        akpm@...ux-foundation.org, zhaoyang.huang@...soc.com,
        yuzhao@...gle.com, surenb@...gle.com, kaleshsingh@...gle.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Multi-gen LRU: skip CMA pages when they are not eligible

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>
> ---
>   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.

-- 
Cheers,

David / dhildenb