From: Zi Yan <ziy@xxxxxxxxxx>
migrate_pages() supports >0 order folio migration and during compaction,
even if compaction_alloc() cannot provide >0 order free pages,
migrate_pages() can split the source page and try to migrate the base
pages from the split. It can be a baseline and start point for adding
support for compacting >0 order folios.
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Suggested-by: Huang Ying <ying.huang@xxxxxxxxx>
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Tested-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Tested-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Adam Manzanares <a.manzanares@xxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Yin Fengwei <fengwei.yin@xxxxxxxxx>
---
mm/compaction.c | 101 ++++++++++++++++++++++++++++++++++++------------
1 file changed, 76 insertions(+), 25 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index ccd447282665..6509fab27be9 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -40,9 +40,22 @@ static inline void count_compact_events(enum vm_event_item item, long delta)
{
count_vm_events(item, delta);
}
+
+/*
+ * order == -1 is expected when compacting proactively via
+ * 1. /proc/sys/vm/compact_memory
+ * 2. /sys/devices/system/node/nodex/compact
+ * 3. /proc/sys/vm/compaction_proactiveness
+ */
+static inline bool is_via_compact_memory(int order)
+{
+ return order == -1;
+}
+
#else
#define count_compact_event(item) do { } while (0)
#define count_compact_events(item, delta) do { } while (0)
+static inline bool is_via_compact_memory(int order) { return false; }
#endif
#if defined CONFIG_COMPACTION || defined CONFIG_CMA
@@ -816,6 +829,32 @@ static bool too_many_isolated(struct compact_control *cc)
return too_many;
}
+/**
+ * skip_isolation_on_order() - determine when to skip folio isolation based on
+ * folio order and compaction target order
+ * @order: to-be-isolated folio order
+ * @target_order: compaction target order
+ *
+ * This avoids unnecessary folio isolations during compaction.
+ */
+static bool skip_isolation_on_order(int order, int target_order)
+{
+ /*
+ * Unless we are performing global compaction (i.e.,
+ * is_via_compact_memory), skip any folios that are larger than the
+ * target order: we wouldn't be here if we'd have a free folio with
+ * the desired target_order, so migrating this folio would likely fail
+ * later.
+ */
+ if (!is_via_compact_memory(target_order) && order >= target_order)
+ return true;
+ /*
+ * We limit memory compaction to pageblocks and won't try
+ * creating free blocks of memory that are larger than that.
+ */
+ return order >= pageblock_order;
+}
+
/**
* isolate_migratepages_block() - isolate all migrate-able pages within
* a single pageblock
@@ -947,7 +986,22 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
valid_page = page;
}
- if (PageHuge(page) && cc->alloc_contig) {
+ if (PageHuge(page)) {
+ /*
+ * skip hugetlbfs if we are not compacting for pages
+ * bigger than its order. THPs and other compound pages
+ * are handled below.
+ */
+ if (!cc->alloc_contig) {
+ const unsigned int order = compound_order(page);
+
+ if (order <= MAX_PAGE_ORDER) {
+ low_pfn += (1UL << order) - 1;
+ nr_scanned += (1UL << order) - 1;
+ }
+ goto isolate_fail;
+ }
+ /* for alloc_contig case */
if (locked) {
unlock_page_lruvec_irqrestore(locked, flags);
locked = NULL;
@@ -1008,21 +1062,24 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
}
/*
- * Regardless of being on LRU, compound pages such as THP and
- * hugetlbfs are not to be compacted unless we are attempting
- * an allocation much larger than the huge page size (eg CMA).
- * We can potentially save a lot of iterations if we skip them
- * at once. The check is racy, but we can consider only valid
- * values and the only danger is skipping too much.
+ * Regardless of being on LRU, compound pages such as THP
+ * (hugetlbfs is handled above) are not to be compacted unless
+ * we are attempting an allocation larger than the compound
+ * page size. We can potentially save a lot of iterations if we
+ * skip them at once. The check is racy, but we can consider
+ * only valid values and the only danger is skipping too much.
*/
if (PageCompound(page) && !cc->alloc_contig) {
const unsigned int order = compound_order(page);
- if (likely(order <= MAX_PAGE_ORDER)) {
- low_pfn += (1UL << order) - 1;
- nr_scanned += (1UL << order) - 1;
+ /* Skip based on page order and compaction target order. */
+ if (skip_isolation_on_order(order, cc->order)) {
+ if (order <= MAX_PAGE_ORDER) {
+ low_pfn += (1UL << order) - 1;
+ nr_scanned += (1UL << order) - 1;
+ }
+ goto isolate_fail;
}
- goto isolate_fail;
}
/*
@@ -1165,10 +1222,11 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
}
/*
- * folio become large since the non-locked check,
- * and it's on LRU.
+ * Check LRU folio order under the lock
*/
- if (unlikely(folio_test_large(folio) && !cc->alloc_contig)) {
+ if (unlikely(skip_isolation_on_order(folio_order(folio),
+ cc->order) &&
+ !cc->alloc_contig)) {
low_pfn += folio_nr_pages(folio) - 1;
nr_scanned += folio_nr_pages(folio) - 1;
folio_set_lru(folio);
@@ -1788,6 +1846,10 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
struct compact_control *cc = (struct compact_control *)data;
struct folio *dst;
+ /* this makes migrate_pages() split the source page and retry */
+ if (folio_test_large(src))
+ return NULL;
+
if (list_empty(&cc->freepages)) {
isolate_freepages(cc);
@@ -2090,17 +2152,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
}
-/*
- * order == -1 is expected when compacting proactively via
- * 1. /proc/sys/vm/compact_memory
- * 2. /sys/devices/system/node/nodex/compact
- * 3. /proc/sys/vm/compaction_proactiveness
- */
-static inline bool is_via_compact_memory(int order)
-{
- return order == -1;
-}
-
/*
* Determine whether kswapd is (or recently was!) running on this node.
*
--
2.43.0
