linux-kernel - Re: [PATCH v2 4/8] mm: migrate: use a folio in migrate_misplaced

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Message-ID: <855536BE-766C-49B2-B358-6C0548760929@nvidia.com>
Date:   Mon, 28 Aug 2023 10:10:25 -0400
From:   Zi Yan <ziy@...dia.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, willy@...radead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        ying.huang@...el.com, david@...hat.com,
        Mike Kravetz <mike.kravetz@...cle.com>, hughd@...gle.com
Subject: Re: [PATCH v2 4/8] mm: migrate: use a folio in
 migrate_misplaced_page()

On 21 Aug 2023, at 7:56, Kefeng Wang wrote:

> Use a folio in migrate_misplaced_page() to save compound_head() calls.
>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
>  mm/migrate.c | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)

LGTM. And a comment below. Reveiwed-by: Zi Yan <ziy@...dia.com>

>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 281eafdf8e63..fc728f9a383f 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2521,17 +2521,18 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
>  			   int node)
>  {
>  	pg_data_t *pgdat = NODE_DATA(node);
> +	struct folio *folio = page_folio(page);
>  	int isolated;
>  	int nr_remaining;
>  	unsigned int nr_succeeded;
>  	LIST_HEAD(migratepages);
> -	int nr_pages = thp_nr_pages(page);
> +	int nr_pages = folio_nr_pages(folio);
>
>  	/*
>  	 * Don't migrate file pages that are mapped in multiple processes
>  	 * with execute permissions as they are probably shared libraries.
>  	 */
> -	if (page_mapcount(page) != 1 && page_is_file_lru(page) &&
> +	if (page_mapcount(page) != 1 && folio_is_file_lru(folio) &&

page_mapcount() is not converted, since folio_mapcount() is not equivalent
to page_mapcount(). It can be converted and this function can be converted
to migrate_misplaced_folio() once we have something like folio_num_sharers().

>  	    (vma->vm_flags & VM_EXEC))
>  		goto out;
>
> @@ -2539,29 +2540,29 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
>  	 * Also do not migrate dirty pages as not all filesystems can move
>  	 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
>  	 */
> -	if (page_is_file_lru(page) && PageDirty(page))
> +	if (folio_is_file_lru(folio) && folio_test_dirty(folio))
>  		goto out;
>
> -	isolated = numamigrate_isolate_folio(pgdat, page_folio(page));
> +	isolated = numamigrate_isolate_folio(pgdat, folio);
>  	if (!isolated)
>  		goto out;
>
> -	list_add(&page->lru, &migratepages);
> +	list_add(&folio->lru, &migratepages);
>  	nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_folio,
>  				     NULL, node, MIGRATE_ASYNC,
>  				     MR_NUMA_MISPLACED, &nr_succeeded);
>  	if (nr_remaining) {
>  		if (!list_empty(&migratepages)) {
> -			list_del(&page->lru);
> -			mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
> -					page_is_file_lru(page), -nr_pages);
> -			putback_lru_page(page);
> +			list_del(&folio->lru);
> +			node_stat_mod_folio(folio, NR_ISOLATED_ANON +
> +					folio_is_file_lru(folio), -nr_pages);
> +			folio_putback_lru(folio);
>  		}
>  		isolated = 0;
>  	}
>  	if (nr_succeeded) {
>  		count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
> -		if (!node_is_toptier(page_to_nid(page)) && node_is_toptier(node))
> +		if (!node_is_toptier(folio_nid(folio)) && node_is_toptier(node))
>  			mod_node_page_state(pgdat, PGPROMOTE_SUCCESS,
>  					    nr_succeeded);
>  	}
> @@ -2569,7 +2570,7 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
>  	return isolated;
>
>  out:
> -	put_page(page);
> +	folio_put(folio);
>  	return 0;
>  }
>  #endif /* CONFIG_NUMA_BALANCING */
> -- 
> 2.41.0


--
Best Regards,
Yan, Zi

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