linux-kernel - Re: [PATCH 4/8] mm/swap: Use PG_dropbehind instead of PG

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Message-ID: <cb057735-c4e6-439a-aada-9432aae3fed6@redhat.com>
Date: Mon, 13 Jan 2025 11:07:07 +0100
From: David Hildenbrand <david@...hat.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>, Jens Axboe <axboe@...nel.dk>
Cc: "Jason A. Donenfeld" <Jason@...c4.com>,
 Andi Shyti <andi.shyti@...ux.intel.com>,
 Chengming Zhou <chengming.zhou@...ux.dev>,
 Christian Brauner <brauner@...nel.org>,
 Christophe Leroy <christophe.leroy@...roup.eu>,
 Dan Carpenter <dan.carpenter@...aro.org>, David Airlie <airlied@...il.com>,
 Hao Ge <gehao@...inos.cn>, Jani Nikula <jani.nikula@...ux.intel.com>,
 Johannes Weiner <hannes@...xchg.org>,
 Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
 Josef Bacik <josef@...icpanda.com>, Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Miklos Szeredi <miklos@...redi.hu>, Nhat Pham <nphamcs@...il.com>,
 Oscar Salvador <osalvador@...e.de>, Ran Xiaokai <ran.xiaokai@....com.cn>,
 Rodrigo Vivi <rodrigo.vivi@...el.com>, Simona Vetter <simona@...ll.ch>,
 Steven Rostedt <rostedt@...dmis.org>, Tvrtko Ursulin <tursulin@...ulin.net>,
 Vlastimil Babka <vbabka@...e.cz>, Yosry Ahmed <yosryahmed@...gle.com>,
 Yu Zhao <yuzhao@...gle.com>, intel-gfx@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 4/8] mm/swap: Use PG_dropbehind instead of PG_reclaim

On 13.01.25 10:34, Kirill A. Shutemov wrote:
> The recently introduced PG_dropbehind allows for freeing folios
> immediately after writeback. Unlike PG_reclaim, it does not need vmscan
> to be involved to get the folio freed.
> 
> Instead of using folio_set_reclaim(), use folio_set_dropbehind() in
> lru_deactivate_file().
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>   mm/swap.c | 8 +-------
>   1 file changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/mm/swap.c b/mm/swap.c
> index fc8281ef4241..4eb33b4804a8 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -562,14 +562,8 @@ static void lru_deactivate_file(struct lruvec *lruvec, struct folio *folio)
>   	folio_clear_referenced(folio);
>   
>   	if (folio_test_writeback(folio) || folio_test_dirty(folio)) {
> -		/*
> -		 * Setting the reclaim flag could race with
> -		 * folio_end_writeback() and confuse readahead.  But the
> -		 * race window is _really_ small and  it's not a critical
> -		 * problem.
> -		 */
>   		lruvec_add_folio(lruvec, folio);
> -		folio_set_reclaim(folio);
> +		folio_set_dropbehind(folio);
>   	} else {
>   		/*
>   		 * The folio's writeback ended while it was in the batch.

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb