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

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Date:   Wed, 19 Apr 2023 14:06:05 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     "zhaoyang.huang" <zhaoyang.huang@...soc.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        Zhaoyang Huang <huangzhaoyang@...il.com>, <ke.wang@...soc.com>
Subject: Re: [PATCH] mm: skip CMA pages when they are not available

"zhaoyang.huang" <zhaoyang.huang@...soc.com> writes:

> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
>
> 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?

Best Regards,
Huang, Ying

> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> ---
>  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;