diff mbox series

[082/156] mm/page_alloc: place pages to tail in __free_pages_core()

Message ID 20201016024628.CwIUohTl6%akpm@linux-foundation.org
State New
Headers show
Series [001/156] device-dax/kmem: fix resource release | expand

Commit Message

Andrew Morton Oct. 16, 2020, 2:46 a.m. UTC
From: David Hildenbrand <david@redhat.com>
Subject: mm/page_alloc: place pages to tail in __free_pages_core()

__free_pages_core() is used when exposing fresh memory to the buddy during
system boot and when onlining memory in generic_online_page().

generic_online_page() is used in two cases:

1. Direct memory onlining in online_pages().
2. Deferred memory onlining in memory-ballooning-like mechanisms (HyperV
   balloon and virtio-mem), when parts of a section are kept
   fake-offline to be fake-onlined later on.

In 1, we already place pages to the tail of the freelist.  Pages will be
freed to MIGRATE_ISOLATE lists first and moved to the tail of the
freelists via undo_isolate_page_range().

In 2, we currently don't implement a proper rule.  In case of virtio-mem,
where we currently always online MAX_ORDER - 1 pages, the pages will be
placed to the HEAD of the freelist - undesireable.  While the hyper-v
balloon calls generic_online_page() with single pages, usually it will
call it on successive single pages in a larger block.

The pages are fresh, so place them to the tail of the freelist and avoid
the PCP.  In __free_pages_core(), remove the now superflouos call to
set_page_refcounted() and add a comment regarding page initialization and
the refcount.

Note: In 2.  we currently don't shuffle.  If ever relevant (page shuffling
is usually of limited use in virtualized environments), we might want to
shuffle after a sequence of generic_online_page() calls in the relevant

Link: https://lkml.kernel.org/r/20201005121534.15649-5-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Reviewed-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Scott Cheloha <cheloha@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

 mm/page_alloc.c |   33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)
diff mbox series


--- a/mm/page_alloc.c~mm-page_alloc-place-pages-to-tail-in-__free_pages_core
+++ a/mm/page_alloc.c
@@ -275,7 +275,8 @@  bool pm_suspended_storage(void)
 unsigned int pageblock_order __read_mostly;
-static void __free_pages_ok(struct page *page, unsigned int order);
+static void __free_pages_ok(struct page *page, unsigned int order,
+			    fpi_t fpi_flags);
  * results with 256, 32 in the lowmem_reserve sysctl:
@@ -687,7 +688,7 @@  out:
 void free_compound_page(struct page *page)
-	__free_pages_ok(page, compound_order(page));
+	__free_pages_ok(page, compound_order(page), FPI_NONE);
 void prep_compound_page(struct page *page, unsigned int order)
@@ -1423,14 +1424,14 @@  static void free_pcppages_bulk(struct zo
 static void free_one_page(struct zone *zone,
 				struct page *page, unsigned long pfn,
 				unsigned int order,
-				int migratetype)
+				int migratetype, fpi_t fpi_flags)
 	if (unlikely(has_isolate_pageblock(zone) ||
 		is_migrate_isolate(migratetype))) {
 		migratetype = get_pfnblock_migratetype(page, pfn);
-	__free_one_page(page, pfn, zone, order, migratetype, FPI_NONE);
+	__free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
@@ -1508,7 +1509,8 @@  void __meminit reserve_bootmem_region(ph
-static void __free_pages_ok(struct page *page, unsigned int order)
+static void __free_pages_ok(struct page *page, unsigned int order,
+			    fpi_t fpi_flags)
 	unsigned long flags;
 	int migratetype;
@@ -1520,7 +1522,8 @@  static void __free_pages_ok(struct page
 	migratetype = get_pfnblock_migratetype(page, pfn);
 	__count_vm_events(PGFREE, 1 << order);
-	free_one_page(page_zone(page), page, pfn, order, migratetype);
+	free_one_page(page_zone(page), page, pfn, order, migratetype,
+		      fpi_flags);
@@ -1530,6 +1533,11 @@  void __free_pages_core(struct page *page
 	struct page *p = page;
 	unsigned int loop;
+	/*
+	 * When initializing the memmap, __init_single_page() sets the refcount
+	 * of all pages to 1 ("allocated"/"not free"). We have to set the
+	 * refcount of all involved pages to 0.
+	 */
 	for (loop = 0; loop < (nr_pages - 1); loop++, p++) {
 		prefetchw(p + 1);
@@ -1540,8 +1548,12 @@  void __free_pages_core(struct page *page
 	set_page_count(p, 0);
 	atomic_long_add(nr_pages, &page_zone(page)->managed_pages);
-	set_page_refcounted(page);
-	__free_pages(page, order);
+	/*
+	 * Bypass PCP and place fresh pages right to the tail, primarily
+	 * relevant for memory onlining.
+	 */
+	__free_pages_ok(page, order, FPI_TO_TAIL);
@@ -3168,7 +3180,8 @@  static void free_unref_page_commit(struc
 	if (migratetype >= MIGRATE_PCPTYPES) {
 		if (unlikely(is_migrate_isolate(migratetype))) {
-			free_one_page(zone, page, pfn, 0, migratetype);
+			free_one_page(zone, page, pfn, 0, migratetype,
+				      FPI_NONE);
 		migratetype = MIGRATE_MOVABLE;
@@ -4991,7 +5004,7 @@  static inline void free_the_page(struct
 	if (order == 0)		/* Via pcp? */
-		__free_pages_ok(page, order);
+		__free_pages_ok(page, order, FPI_NONE);
 void __free_pages(struct page *page, unsigned int order)