+ mm-page_alloc-move-pages-to-tail-in-move_to_free_list.patch added to -mm tree

+ mm-page_alloc-move-pages-to-tail-in-move_to_free_list.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/page_alloc: move pages to tail in move_to_free_list()
has been added to the -mm tree.  Its filename is
     mm-page_alloc-move-pages-to-tail-in-move_to_free_list.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-move-pages-to-tail-in-move_to_free_list.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-move-pages-to-tail-in-move_to_free_list.patch

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------------------------------------------------------
From: David Hildenbrand <david@redhat.com>
Subject: mm/page_alloc: move pages to tail in move_to_free_list()

Whenever we move pages between freelists via move_to_free_list()/
move_freepages_block(), we don't actually touch the pages:
1. Page isolation doesn't actually touch the pages, it simply isolates
   pageblocks and moves all free pages to the MIGRATE_ISOLATE freelist.
   When undoing isolation, we move the pages back to the target list.
2. Page stealing (steal_suitable_fallback()) moves free pages directly
   between lists without touching them.
3. reserve_highatomic_pageblock()/unreserve_highatomic_pageblock() moves
   free pages directly between freelists without touching them.

We already place pages to the tail of the freelists when undoing isolation
via __putback_isolated_page(), let's do it in any case (e.g., if order <=
pageblock_order) and document the behavior. To simplify, let's move the
pages to the tail for all move_to_free_list()/move_freepages_block() users.

In 2., the target list is empty, so there should be no change.  In 3., we
might observe a change, however, highatomic is more concerned about
allocations succeeding than cache hotness - if we ever realize this change
degrades a workload, we can special-case this instance and add a proper
comment.

This change results in all pages getting onlined via online_pages() to be
placed to the tail of the freelist.

Link: https://lkml.kernel.org/r/20201005121534.15649-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
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>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Scott Cheloha <cheloha@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c     |   10 +++++++---
 mm/page_isolation.c |    5 +++++
 2 files changed, 12 insertions(+), 3 deletions(-)

--- a/mm/page_alloc.c~mm-page_alloc-move-pages-to-tail-in-move_to_free_list
+++ a/mm/page_alloc.c
@@ -901,13 +901,17 @@ static inline void add_to_free_list_tail
 	area->nr_free++;
 }
 
-/* Used for pages which are on another list */
+/*
+ * Used for pages which are on another list. Move the pages to the tail
+ * of the list - so the moved pages won't immediately be considered for
+ * allocation again (e.g., optimization for memory onlining).
+ */
 static inline void move_to_free_list(struct page *page, struct zone *zone,
 				     unsigned int order, int migratetype)
 {
 	struct free_area *area = &zone->free_area[order];
 
-	list_move(&page->lru, &area->free_list[migratetype]);
+	list_move_tail(&page->lru, &area->free_list[migratetype]);
 }
 
 static inline void del_page_from_free_list(struct page *page, struct zone *zone,
@@ -2340,7 +2344,7 @@ static inline struct page *__rmqueue_cma
 #endif
 
 /*
- * Move the free pages in a range to the free lists of the requested type.
+ * Move the free pages in a range to the freelist tail of the requested type.
  * Note that start_page and end_pages are not aligned on a pageblock
  * boundary. If alignment is required, use move_freepages_block()
  */
--- a/mm/page_isolation.c~mm-page_alloc-move-pages-to-tail-in-move_to_free_list
+++ a/mm/page_isolation.c
@@ -106,6 +106,11 @@ static void unset_migratetype_isolate(st
 	 * If we isolate freepage with more than pageblock_order, there
 	 * should be no freepage in the range, so we could avoid costly
 	 * pageblock scanning for freepage moving.
+	 *
+	 * We didn't actually touch any of the isolated pages, so place them
+	 * to the tail of the freelist. This is an optimization for memory
+	 * onlining - just onlined memory won't immediately be considered for
+	 * allocation.
 	 */
 	if (!isolated_page) {
 		nr_pages = move_freepages_block(zone, page, migratetype, NULL);
_

Patches currently in -mm which might be from david@redhat.com are

mm-page_alloc-tweak-comments-in-has_unmovable_pages.patch
mm-page_isolation-exit-early-when-pageblock-is-isolated-in-set_migratetype_isolate.patch
mm-page_isolation-drop-warn_on_once-in-set_migratetype_isolate.patch
mm-page_isolation-cleanup-set_migratetype_isolate.patch
virtio-mem-dont-special-case-zone_movable.patch
mm-document-semantics-of-zone_movable.patch
mm-memory_hotplug-inline-__offline_pages-into-offline_pages.patch
mm-memory_hotplug-enforce-section-granularity-when-onlining-offlining.patch
mm-memory_hotplug-simplify-page-offlining.patch
mm-page_alloc-simplify-__offline_isolated_pages.patch
mm-memory_hotplug-drop-nr_isolate_pageblock-in-offline_pages.patch
mm-page_isolation-simplify-return-value-of-start_isolate_page_range.patch
mm-memory_hotplug-simplify-page-onlining.patch
mm-page_alloc-drop-stale-pageblock-comment-in-memmap_init_zone.patch
mm-pass-migratetype-into-memmap_init_zone-and-move_pfn_range_to_zone.patch
mm-memory_hotplug-mark-pageblocks-migrate_isolate-while-onlining-memory.patch
kernel-resource-make-release_mem_region_adjustable-never-fail.patch
kernel-resource-move-and-rename-ioresource_mem_driver_managed.patch
mm-memory_hotplug-guard-more-declarations-by-config_memory_hotplug.patch
mm-memory_hotplug-prepare-passing-flags-to-add_memory-and-friends.patch
mm-memory_hotplug-memhp_merge_resource-to-specify-merging-of-system-ram-resources.patch
virtio-mem-try-to-merge-system-ram-resources.patch
xen-balloon-try-to-merge-system-ram-resources.patch
hv_balloon-try-to-merge-system-ram-resources.patch
kernel-resource-make-iomem_resource-implicit-in-release_mem_region_adjustable.patch
mm-page_alloc-convert-report-flag-of-__free_one_page-to-a-proper-flag.patch
mm-page_alloc-place-pages-to-tail-in-__putback_isolated_page.patch
mm-page_alloc-move-pages-to-tail-in-move_to_free_list.patch
mm-page_alloc-place-pages-to-tail-in-__free_pages_core.patch
mm-memory_hotplug-update-comment-regarding-zone-shuffling.patch