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authorDavid Hildenbrand <david@redhat.com>2020-10-15 20:09:30 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-10-16 11:11:18 -0700
commit293ffa5ebb9c08a77d8de458166c31b4d7b0cd65 (patch)
tree0e97070f6b2a70fae44904bd0e9515d62a44bfda /mm/page_isolation.c
parent47b6a24a23825ae7b33ff11396980da7c353843d (diff)
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. Signed-off-by: David Hildenbrand <david@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Oscar Salvador <osalvador@suse.de> Reviewed-by: Wei Yang <richard.weiyang@linux.alibaba.com> Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.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: 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> Link: https://lkml.kernel.org/r/20201005121534.15649-4-david@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_isolation.c')
-rw-r--r--mm/page_isolation.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index abfe26ad59fd..83692b937784 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -106,6 +106,11 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
* 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);