+ mm-page_alloc-place-pages-to-tail-in-__free_pages_core.patch added to -mm tree

+ mm-page_alloc-place-pages-to-tail-in-__free_pages_core.patch added to -mm tree

[akpm]

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

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

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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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------------------------------------------------------
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
callers.

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(-)

--- 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;
 #endif
 
-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)
 {
 	mem_cgroup_uncharge(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)
 {
 	spin_lock(&zone->lock);
 	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);
 	spin_unlock(&zone->lock);
 }
 
@@ -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);
 	local_irq_save(flags);
 	__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);
 	local_irq_restore(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.
+	 */
 	prefetchw(p);
 	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);
 }
 
 #ifdef CONFIG_NEED_MULTIPLE_NODES
@@ -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);
 			return;
 		}
 		migratetype = MIGRATE_MOVABLE;
@@ -4991,7 +5004,7 @@ static inline void free_the_page(struct
 	if (order == 0)		/* Via pcp? */
 		free_unref_page(page);
 	else
-		__free_pages_ok(page, order);
+		__free_pages_ok(page, order, FPI_NONE);
 }
 
 void __free_pages(struct page *page, unsigned int order)
_

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