diff mbox series

[1/6] mm/page_alloc: Add page->buddy_list and page->pcp_list

Message ID 20220509130805.20335-2-mgorman@techsingularity.net (mailing list archive)
State New
Headers show
Series Drain remote per-cpu directly v2 | expand

Commit Message

Mel Gorman May 9, 2022, 1:08 p.m. UTC 
The page allocator uses page->lru for storing pages on either buddy or
PCP lists. Create page->buddy_list and page->pcp_list as a union with
page->lru. This is simply to clarify what type of list a page is on
in the page allocator.

No functional change intended.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 include/linux/mm_types.h |  5 +++++
 mm/page_alloc.c          | 18 +++++++++---------
 2 files changed, 14 insertions(+), 9 deletions(-)

Comments

Muchun Song May 13, 2022, 8:41 a.m. UTC | #1 
On Mon, May 09, 2022 at 02:08:00PM +0100, Mel Gorman wrote:
> The page allocator uses page->lru for storing pages on either buddy or
> PCP lists. Create page->buddy_list and page->pcp_list as a union with
> page->lru. This is simply to clarify what type of list a page is on
> in the page allocator.
> 
> No functional change intended.
> 

Nice cleanup for me.

> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> ---
>  include/linux/mm_types.h |  5 +++++
>  mm/page_alloc.c          | 18 +++++++++---------
>  2 files changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 8834e38c06a4..a2782e8af307 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -87,6 +87,7 @@ struct page {
>  			 */
>  			union {
>  				struct list_head lru;
> +
>  				/* Or, for the Unevictable "LRU list" slot */
>  				struct {
>  					/* Always even, to negate PageTail */
> @@ -94,6 +95,10 @@ struct page {
>  					/* Count page's or folio's mlocks */
>  					unsigned int mlock_count;
>  				};
> +
> +				/* Or, free page */
> +				struct list_head buddy_list;
> +				struct list_head pcp_list;
>  			};

Since you have clarified "lru" member, should we go further?
Like union "index" to "pcp_migratetype" and "private" to "order"
since buddy allocator reuses "index" and "private" as well.
My initial idea is as follows, it is more clear for me, what
do you think?

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index dbfd892ac96a..644349a5f901 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -107,6 +107,15 @@ struct page {
                         */
                        unsigned long private;
                };
+               struct {        /* pages manipulated by buddy allocator */
+                       union {
+                               struct list_head buddy_list;
+                               struct list_head pcp_list;
+                       };
+                       unsigned long mapping_pad;      /* Not used */
+                       unsigned long pcp_migratetype;
+                       unsigned long order;
+               };
                struct {        /* page_pool used by netstack */
                        /**
                         * @pp_magic: magic value to avoid recycling non
Mel Gorman May 26, 2022, 10:14 a.m. UTC | #2 
On Fri, May 13, 2022 at 04:41:20PM +0800, Muchun Song wrote:
> > @@ -94,6 +95,10 @@ struct page {
> >  					/* Count page's or folio's mlocks */
> >  					unsigned int mlock_count;
> >  				};
> > +
> > +				/* Or, free page */
> > +				struct list_head buddy_list;
> > +				struct list_head pcp_list;
> >  			};
> 
> Since you have clarified "lru" member, should we go further?
> Like union "index" to "pcp_migratetype" and "private" to "order"
> since buddy allocator reuses "index" and "private" as well.
> My initial idea is as follows, it is more clear for me, what
> do you think?
> 

I think it would be more appropriate to split it out as a separate type as
suggested by Matthew Wilcox. While I would not be opposed to your approach
as such, it's outside the context of the series which is modifying how
PCP works.
diff mbox series

Patch

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 8834e38c06a4..a2782e8af307 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -87,6 +87,7 @@  struct page {
 			 */
 			union {
 				struct list_head lru;
+
 				/* Or, for the Unevictable "LRU list" slot */
 				struct {
 					/* Always even, to negate PageTail */
@@ -94,6 +95,10 @@  struct page {
 					/* Count page's or folio's mlocks */
 					unsigned int mlock_count;
 				};
+
+				/* Or, free page */
+				struct list_head buddy_list;
+				struct list_head pcp_list;
 			};
 			/* See page-flags.h for PAGE_MAPPING_FLAGS */
 			struct address_space *mapping;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2db95780e003..63976ad4b7f1 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -780,7 +780,7 @@  static inline bool set_page_guard(struct zone *zone, struct page *page,
 		return false;
 
 	__SetPageGuard(page);
-	INIT_LIST_HEAD(&page->lru);
+	INIT_LIST_HEAD(&page->buddy_list);
 	set_page_private(page, order);
 	/* Guard pages are not available for any usage */
 	__mod_zone_freepage_state(zone, -(1 << order), migratetype);
@@ -957,7 +957,7 @@  static inline void add_to_free_list(struct page *page, struct zone *zone,
 {
 	struct free_area *area = &zone->free_area[order];
 
-	list_add(&page->lru, &area->free_list[migratetype]);
+	list_add(&page->buddy_list, &area->free_list[migratetype]);
 	area->nr_free++;
 }
 
@@ -967,7 +967,7 @@  static inline void add_to_free_list_tail(struct page *page, struct zone *zone,
 {
 	struct free_area *area = &zone->free_area[order];
 
-	list_add_tail(&page->lru, &area->free_list[migratetype]);
+	list_add_tail(&page->buddy_list, &area->free_list[migratetype]);
 	area->nr_free++;
 }
 
@@ -981,7 +981,7 @@  static inline void move_to_free_list(struct page *page, struct zone *zone,
 {
 	struct free_area *area = &zone->free_area[order];
 
-	list_move_tail(&page->lru, &area->free_list[migratetype]);
+	list_move_tail(&page->buddy_list, &area->free_list[migratetype]);
 }
 
 static inline void del_page_from_free_list(struct page *page, struct zone *zone,
@@ -991,7 +991,7 @@  static inline void del_page_from_free_list(struct page *page, struct zone *zone,
 	if (page_reported(page))
 		__ClearPageReported(page);
 
-	list_del(&page->lru);
+	list_del(&page->buddy_list);
 	__ClearPageBuddy(page);
 	set_page_private(page, 0);
 	zone->free_area[order].nr_free--;
@@ -1493,7 +1493,7 @@  static void free_pcppages_bulk(struct zone *zone, int count,
 			mt = get_pcppage_migratetype(page);
 
 			/* must delete to avoid corrupting pcp list */
-			list_del(&page->lru);
+			list_del(&page->pcp_list);
 			count -= nr_pages;
 			pcp->count -= nr_pages;
 
@@ -3053,7 +3053,7 @@  static int rmqueue_bulk(struct zone *zone, unsigned int order,
 		 * for IO devices that can merge IO requests if the physical
 		 * pages are ordered properly.
 		 */
-		list_add_tail(&page->lru, list);
+		list_add_tail(&page->pcp_list, list);
 		allocated++;
 		if (is_migrate_cma(get_pcppage_migratetype(page)))
 			__mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
@@ -3392,7 +3392,7 @@  static void free_unref_page_commit(struct page *page, int migratetype,
 	__count_vm_event(PGFREE);
 	pcp = this_cpu_ptr(zone->per_cpu_pageset);
 	pindex = order_to_pindex(migratetype, order);
-	list_add(&page->lru, &pcp->lists[pindex]);
+	list_add(&page->pcp_list, &pcp->lists[pindex]);
 	pcp->count += 1 << order;
 
 	/*
@@ -3656,7 +3656,7 @@  struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
 		}
 
 		page = list_first_entry(list, struct page, lru);
-		list_del(&page->lru);
+		list_del(&page->pcp_list);
 		pcp->count -= 1 << order;
 	} while (check_new_pcp(page, order));