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mm: page_alloc: avoid merging non-fallbackable pageblocks with others 

This is done in addition to MIGRATE_ISOLATE pageblock merge avoidance.
It prepares for the upcoming removal of the MAX_ORDER-1 alignment
requirement for CMA and alloc_contig_range().

MIGRATE_HIGHATOMIC should not merge with other migratetypes like
MIGRATE_ISOLATE and MIGRARTE_CMA[1], so this commit prevents that too.

Remove MIGRATE_CMA and MIGRATE_ISOLATE from fallbacks list, since they
are never used.

[1] https://lore.kernel.org/linux-mm/20211130100853.GP3366@techsingularity.net/

Link: https://lkml.kernel.org/r/20220124175957.1261961-1-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Zi Yan 2022-03-22 14:43:05 -07:00 committed by Linus Torvalds
parent ff11a7ce1f
commit 1dd214b8f2
2 changed files with 32 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
include/linux/mmzone.h
View File

@ -83,6 +83,17 @@ static inline bool is_migrate_movable(int mt)
return is_migrate_cma(mt) || mt == MIGRATE_MOVABLE;
}
/*
* Check whether a migratetype can be merged with another migratetype.
*
* It is only mergeable when it can fall back to other migratetypes for
* allocation. See fallbacks[MIGRATE_TYPES][3] in page_alloc.c.
*/
static inline bool migratetype_is_mergeable(int mt)
{
return mt < MIGRATE_PCPTYPES;
}
#define for_each_migratetype_order(order, type) \
for (order = 0; order < MAX_ORDER; order++) \
for (type = 0; type < MIGRATE_TYPES; type++)

44
mm/page_alloc.c
View File

@ -1117,25 +1117,24 @@ continue_merging:
}
if (order < MAX_ORDER - 1) {
/* If we are here, it means order is >= pageblock_order.
* We want to prevent merge between freepages on isolate
* pageblock and normal pageblock. Without this, pageblock
* isolation could cause incorrect freepage or CMA accounting.
* We want to prevent merge between freepages on pageblock
* without fallbacks and normal pageblock. Without this,
* pageblock isolation could cause incorrect freepage or CMA
* accounting or HIGHATOMIC accounting.
*
* We don't want to hit this code for the more frequent
* low-order merging.
*/
if (unlikely(has_isolate_pageblock(zone))) {
int buddy_mt;
int buddy_mt;
buddy_pfn = __find_buddy_pfn(pfn, order);
buddy = page + (buddy_pfn - pfn);
buddy_mt = get_pageblock_migratetype(buddy);
buddy_pfn = __find_buddy_pfn(pfn, order);
buddy = page + (buddy_pfn - pfn);
buddy_mt = get_pageblock_migratetype(buddy);
if (migratetype != buddy_mt
&& (is_migrate_isolate(migratetype) ||
is_migrate_isolate(buddy_mt)))
goto done_merging;
}
if (migratetype != buddy_mt
&& (!migratetype_is_mergeable(migratetype) ||
!migratetype_is_mergeable(buddy_mt)))
goto done_merging;
max_order = order + 1;
goto continue_merging;
}
@ -2479,17 +2478,13 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
/*
* This array describes the order lists are fallen back to when
* the free lists for the desirable migrate type are depleted
*
* The other migratetypes do not have fallbacks.
*/
static int fallbacks[MIGRATE_TYPES][3] = {
[MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE, MIGRATE_TYPES },
[MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_TYPES },
[MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE, MIGRATE_TYPES },
#ifdef CONFIG_CMA
[MIGRATE_CMA] = { MIGRATE_TYPES }, /* Never used */
#endif
#ifdef CONFIG_MEMORY_ISOLATION
[MIGRATE_ISOLATE] = { MIGRATE_TYPES }, /* Never used */
#endif
};
#ifdef CONFIG_CMA
@ -2795,8 +2790,8 @@ static void reserve_highatomic_pageblock(struct page *page, struct zone *zone,
/* Yoink! */
mt = get_pageblock_migratetype(page);
if (!is_migrate_highatomic(mt) && !is_migrate_isolate(mt)
&& !is_migrate_cma(mt)) {
/* Only reserve normal pageblocks (i.e., they can merge with others) */
if (migratetype_is_mergeable(mt)) {
zone->nr_reserved_highatomic += pageblock_nr_pages;
set_pageblock_migratetype(page, MIGRATE_HIGHATOMIC);
move_freepages_block(zone, page, MIGRATE_HIGHATOMIC, NULL);
@ -3545,8 +3540,11 @@ int __isolate_free_page(struct page *page, unsigned int order)
struct page *endpage = page + (1 << order) - 1;
for (; page < endpage; page += pageblock_nr_pages) {
int mt = get_pageblock_migratetype(page);
if (!is_migrate_isolate(mt) && !is_migrate_cma(mt)
&& !is_migrate_highatomic(mt))
/*
* Only change normal pageblocks (i.e., they can merge
* with others)
*/
if (migratetype_is_mergeable(mt))
set_pageblock_migratetype(page,
MIGRATE_MOVABLE);
}