The patch titled
Subject: mm/cma: change fallback behaviour for CMA freepage
has been added to the -mm tree. Its filename is
mm-cma-change-fallback-behaviour-for-cma-freepage.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-cma-change-fallback-behaviour-for-cma-freepage.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-cma-change-fallback-behaviour-for-cma-freepage.patch
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From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Subject: mm/cma: change fallback behaviour for CMA freepage
Freepage with MIGRATE_CMA can be used only for MIGRATE_MOVABLE and they
should not be expanded to other migratetype buddy list to protect them
from unmovable/reclaimable allocation. Implementing these requirements in
__rmqueue_fallback(), that is, finding largest possible block of freepage
has bad effect that high order freepage with MIGRATE_CMA are broken
continually although there are suitable order CMA freepage. Reason is
that they are not be expanded to other migratetype buddy list and next
__rmqueue_fallback() invocation try to finds another largest block of
freepage and break it again. So, MIGRATE_CMA fallback should be handled
separately. This patch introduces __rmqueue_cma_fallback(), that just
wrapper of __rmqueue_smallest() and call it before __rmqueue_fallback() if
migratetype == MIGRATE_MOVABLE.
This results in unintended behaviour change that MIGRATE_CMA freepage is
always used first rather than other migratetype as movable allocation's
fallback. But, as already mentioned above, MIGRATE_CMA can be used only
for MIGRATE_MOVABLE, so it is better to use MIGRATE_CMA freepage first as
much as possible. Otherwise, we needlessly take up precious freepages
with other migratetype and increase chance of fragmentation.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 36 +++++++++++++++++++-----------------
1 file changed, 19 insertions(+), 17 deletions(-)
diff -puN mm/page_alloc.c~mm-cma-change-fallback-behaviour-for-cma-freepage mm/page_alloc.c
--- a/mm/page_alloc.c~mm-cma-change-fallback-behaviour-for-cma-freepage
+++ a/mm/page_alloc.c
@@ -1032,11 +1032,9 @@ struct page *__rmqueue_smallest(struct z
static int fallbacks[MIGRATE_TYPES][4] = {
[MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE },
[MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE },
+ [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
#ifdef CONFIG_CMA
- [MIGRATE_MOVABLE] = { MIGRATE_CMA, MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
[MIGRATE_CMA] = { MIGRATE_RESERVE }, /* Never used */
-#else
- [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
#endif
[MIGRATE_RESERVE] = { MIGRATE_RESERVE }, /* Never used */
#ifdef CONFIG_MEMORY_ISOLATION
@@ -1044,6 +1042,17 @@ static int fallbacks[MIGRATE_TYPES][4] =
#endif
};
+#ifdef CONFIG_CMA
+static struct page *__rmqueue_cma_fallback(struct zone *zone,
+ unsigned int order)
+{
+ return __rmqueue_smallest(zone, order, MIGRATE_CMA);
+}
+#else
+static inline struct page *__rmqueue_cma_fallback(struct zone *zone,
+ unsigned int order) { return NULL; }
+#endif
+
/*
* Move the free pages in a range to the free lists of the requested type.
* Note that start_page and end_pages are not aligned on a pageblock
@@ -1195,19 +1204,8 @@ __rmqueue_fallback(struct zone *zone, un
struct page, lru);
area->nr_free--;
- if (!is_migrate_cma(migratetype)) {
- try_to_steal_freepages(zone, page,
- start_migratetype,
- migratetype);
- } else {
- /*
- * When borrowing from MIGRATE_CMA, we need to
- * release the excess buddy pages to CMA
- * itself, and we do not try to steal extra
- * free pages.
- */
- buddy_type = migratetype;
- }
+ try_to_steal_freepages(zone, page, start_migratetype,
+ migratetype);
/* Remove the page from the freelists */
list_del(&page->lru);
@@ -1249,7 +1247,11 @@ retry_reserve:
page = __rmqueue_smallest(zone, order, migratetype);
if (unlikely(!page) && migratetype != MIGRATE_RESERVE) {
- page = __rmqueue_fallback(zone, order, migratetype);
+ if (migratetype == MIGRATE_MOVABLE)
+ page = __rmqueue_cma_fallback(zone, order);
+
+ if (!page)
+ page = __rmqueue_fallback(zone, order, migratetype);
/*
* Use MIGRATE_RESERVE rather than fail an allocation. goto
_
Patches currently in -mm which might be from iamjoonsoo.kim@xxxxxxx are
origin.patch
mm-nommu-fix-memory-leak.patch
zram-use-proper-type-to-update-max_used_pages.patch
mm-cma-debugfs-interface.patch
mm-cma-allocation-trigger.patch
mm-cma-release-trigger.patch
mm-cma-allocation-trigger-fix.patch
mm-cma-change-fallback-behaviour-for-cma-freepage.patch
mm-page_alloc-factor-out-fallback-freepage-checking.patch
mm-compaction-enhance-compaction-finish-condition.patch
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