linux-kernel - Re: [RFC PATCH v0 1/2] migrate: implement migrate_misplaced_folio

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Message-ID: <15744682-72ea-472f-9af1-50c3494c0b78@redhat.com>
Date: Thu, 22 May 2025 17:59:01 +0200
From: David Hildenbrand <david@...hat.com>
To: Bharata B Rao <bharata@....com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Cc: Jonathan.Cameron@...wei.com, dave.hansen@...el.com, gourry@...rry.net,
 hannes@...xchg.org, mgorman@...hsingularity.net, mingo@...hat.com,
 peterz@...radead.org, raghavendra.kt@....com, riel@...riel.com,
 rientjes@...gle.com, sj@...nel.org, weixugc@...gle.com, willy@...radead.org,
 ying.huang@...ux.alibaba.com, ziy@...dia.com, dave@...olabs.net,
 nifan.cxl@...il.com, joshua.hahnjy@...il.com, xuezhengchu@...wei.com,
 yiannis@...corp.com, akpm@...ux-foundation.org
Subject: Re: [RFC PATCH v0 1/2] migrate: implement
 migrate_misplaced_folio_batch

On 21.05.25 10:02, Bharata B Rao wrote:
> From: Gregory Price <gourry@...rry.net>
> 
> A common operation in tiering is to migrate multiple pages at once.
> The migrate_misplaced_folio function requires one call for each
> individual folio.  Expose a batch-variant of the same call for use
> when doing batch migrations.
> 
> Signed-off-by: Gregory Price <gourry@...rry.net>
> Signed-off-by: Bharata B Rao <bharata@....com>
> ---
>   include/linux/migrate.h |  6 ++++++
>   mm/migrate.c            | 31 +++++++++++++++++++++++++++++++
>   2 files changed, 37 insertions(+)
> 
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index aaa2114498d6..c9496adcf192 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -145,6 +145,7 @@ const struct movable_operations *page_movable_ops(struct page *page)
>   int migrate_misplaced_folio_prepare(struct folio *folio,
>   		struct vm_area_struct *vma, int node);
>   int migrate_misplaced_folio(struct folio *folio, int node);
> +int migrate_misplaced_folio_batch(struct list_head *foliolist, int node);
>   #else
>   static inline int migrate_misplaced_folio_prepare(struct folio *folio,
>   		struct vm_area_struct *vma, int node)
> @@ -155,6 +156,11 @@ static inline int migrate_misplaced_folio(struct folio *folio, int node)
>   {
>   	return -EAGAIN; /* can't migrate now */
>   }
> +static inline int migrate_misplaced_folio_batch(struct list_head *foliolist,
> +						int node)
> +{
> +	return -EAGAIN; /* can't migrate now */
> +}
>   #endif /* CONFIG_NUMA_BALANCING */
>   
>   #ifdef CONFIG_MIGRATION
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 676d9cfc7059..32cc2eafb037 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2733,5 +2733,36 @@ int migrate_misplaced_folio(struct folio *folio, int node)
>   	BUG_ON(!list_empty(&migratepages));
>   	return nr_remaining ? -EAGAIN : 0;
>   }
> +
> +/*
> + * Batch variant of migrate_misplaced_folio. Attempts to migrate
> + * a folio list to the specified destination.
> + *
> + * Caller is expected to have isolated the folios by calling
> + * migrate_misplaced_folio_prepare(), which will result in an
> + * elevated reference count on the folio.
> + *
> + * This function will un-isolate the folios, dereference them, and
> + * remove them from the list before returning.
> + */
> +int migrate_misplaced_folio_batch(struct list_head *folio_list, int node)

"migrate_misplaced_folios" ?

:)

-- 
Cheers,

David / dhildenb