Hi,
On 2021/12/10 07:04, Zi Yan wrote:
From: Zi Yan <ziy@xxxxxxxxxx>
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().
MIGRARTE_HIGHATOMIC should not merge with other migratetypes like
MIGRATE_ISOLATE and MIGRARTE_CMA[1], so this commit prevents that too.
Also add MIGRARTE_HIGHATOMIC to fallbacks array for completeness.
[1] https://lore.kernel.org/linux-mm/20211130100853.GP3366@xxxxxxxxxxxxxxxxxxx/
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
include/linux/mmzone.h | 6 ++++++
mm/page_alloc.c | 28 ++++++++++++++++++----------
2 files changed, 24 insertions(+), 10 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 58e744b78c2c..b925431b0123 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -83,6 +83,12 @@ static inline bool is_migrate_movable(int mt)
return is_migrate_cma(mt) || mt == MIGRATE_MOVABLE;
}
+/* See fallbacks[MIGRATE_TYPES][3] in page_alloc.c */
+static inline bool migratetype_has_fallback(int mt)
+{
+ return mt < MIGRATE_PCPTYPES;
+}
+
I would suggest spliting the patch into 2 parts. The first part: no
functioning change, just introduce migratetype_has_fallback()
and replace where it applys to.
#define for_each_migratetype_order(order, type) \
for (order = 0; order < MAX_ORDER; order++) \
for (type = 0; type < MIGRATE_TYPES; type++)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index edfd6c81af82..107a5f186d3b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1041,6 +1041,12 @@ buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,
return page_is_buddy(higher_page, higher_buddy, order + 1);
}
+static inline bool has_non_fallback_pageblock(struct zone *zone)
+{
+ return has_isolate_pageblock(zone) || zone_cma_pages(zone) != 0 ||
+ zone->nr_reserved_highatomic != 0;
Make zone->nr_reserved_highatomic != 0 a helper as zone_cma_pages()?
+}
+
/*
* Freeing function for a buddy system allocator.
*
@@ -1116,14 +1122,15 @@ static inline void __free_one_page(struct page *page,
}
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))) {
+ if (unlikely(has_non_fallback_pageblock(zone))) {
I'm not familiar with the code details, just wondering if this change
would has side effects on cma
pageblock merging as it the condition stronger?
Thanks,
Eric
int buddy_mt;
buddy_pfn = __find_buddy_pfn(pfn, order);
@@ -1131,8 +1138,8 @@ static inline void __free_one_page(struct page *page,
buddy_mt = get_pageblock_migratetype(buddy);
if (migratetype != buddy_mt
- && (is_migrate_isolate(migratetype) ||
- is_migrate_isolate(buddy_mt)))
+ && (!migratetype_has_fallback(migratetype) ||
+ !migratetype_has_fallback(buddy_mt)))
goto done_merging;
}
max_order = order + 1;
@@ -2483,6 +2490,7 @@ 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 },
+ [MIGRATE_HIGHATOMIC] = { MIGRATE_TYPES }, /* Never used */
#ifdef CONFIG_CMA
[MIGRATE_CMA] = { MIGRATE_TYPES }, /* Never used */
#endif
@@ -2794,8 +2802,8 @@ 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 pageblock */
+ if (migratetype_has_fallback(mt)) {
zone->nr_reserved_highatomic += pageblock_nr_pages;
set_pageblock_migratetype(page, MIGRATE_HIGHATOMIC);
move_freepages_block(zone, page, MIGRATE_HIGHATOMIC, NULL);
@@ -3544,8 +3552,8 @@ 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 pageblock */
+ if (migratetype_has_fallback(mt))
set_pageblock_migratetype(page,
MIGRATE_MOVABLE);
}
