From: Gregory Price <gourry@gourry.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@gourry.net>
Signed-off-by: Bharata B Rao <bharata@amd.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 acadd41e0b5c..0593f5869be8 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -107,6 +107,7 @@ static inline int migrate_huge_page_move_mapping(struct address_space *mapping,
 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_folios_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)
@@ -117,6 +118,11 @@ static inline int migrate_misplaced_folio(struct folio *folio, int node)
 {
 	return -EAGAIN; /* can't migrate now */
 }
+static inline int migrate_misplaced_folios_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 7e356c0b1b5a..1268a95eda0e 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2714,5 +2714,36 @@ 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_folios_batch(struct list_head *folio_list, int node)
+{
+	pg_data_t *pgdat = NODE_DATA(node);
+	unsigned int nr_succeeded;
+	int nr_remaining;
+
+	nr_remaining = migrate_pages(folio_list, alloc_misplaced_dst_folio,
+				     NULL, node, MIGRATE_ASYNC,
+				     MR_NUMA_MISPLACED, &nr_succeeded);
+	if (nr_remaining)
+		putback_movable_pages(folio_list);
+
+	if (nr_succeeded) {
+		count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
+		mod_node_page_state(pgdat, PGPROMOTE_SUCCESS, nr_succeeded);
+	}
+	BUG_ON(!list_empty(folio_list));
+	return nr_remaining ? -EAGAIN : 0;
+}
 #endif /* CONFIG_NUMA_BALANCING */
 #endif /* CONFIG_NUMA */
-- 
2.34.1

Bharata B Rao <bharata@amd.com> writes:

> From: Gregory Price <gourry@gourry.net>
>
> A common operation in tiering is to migrate multiple pages at once.

Is it common now?  If so, you can replace some callers of
migrate_misplaced_folio() with migrate_misplaced_folios_batch().

> The migrate_misplaced_folio function requires one call for each

IMHO, migrate_misplaced_folio() is more concise than
migrate_misplaced_folio function.

> individual folio.  Expose a batch-variant of the same call for use
> when doing batch migrations.
>
> Signed-off-by: Gregory Price <gourry@gourry.net>
> Signed-off-by: Bharata B Rao <bharata@amd.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 acadd41e0b5c..0593f5869be8 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -107,6 +107,7 @@ static inline int migrate_huge_page_move_mapping(struct address_space *mapping,
>  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_folios_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)
> @@ -117,6 +118,11 @@ static inline int migrate_misplaced_folio(struct folio *folio, int node)
>  {
>  	return -EAGAIN; /* can't migrate now */
>  }
> +static inline int migrate_misplaced_folios_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 7e356c0b1b5a..1268a95eda0e 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2714,5 +2714,36 @@ 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_folios_batch(struct list_head *folio_list, int node)

In addition to working on a list of folios instead of single folio, I
found there are some difference about memcg counting between
migrate_misplaced_folios_batch() and migrate_misplace_folio().  Why?

And, can we merge the implementation of two functions to reduce code
duplication?

> +{
> +	pg_data_t *pgdat = NODE_DATA(node);
> +	unsigned int nr_succeeded;
> +	int nr_remaining;
> +
> +	nr_remaining = migrate_pages(folio_list, alloc_misplaced_dst_folio,
> +				     NULL, node, MIGRATE_ASYNC,
> +				     MR_NUMA_MISPLACED, &nr_succeeded);
> +	if (nr_remaining)
> +		putback_movable_pages(folio_list);
> +
> +	if (nr_succeeded) {
> +		count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
> +		mod_node_page_state(pgdat, PGPROMOTE_SUCCESS, nr_succeeded);
> +	}
> +	BUG_ON(!list_empty(folio_list));
> +	return nr_remaining ? -EAGAIN : 0;
> +}
>  #endif /* CONFIG_NUMA_BALANCING */
>  #endif /* CONFIG_NUMA */

---
Best Regards,
Huang, Ying