[PATCH 2/2] lru: allow large batched add large folio to lru list

[Yin Fengwei <fengwei.yin@xxxxxxxxx>]

Currently, large folio is not batched added to lru list. Which
cause high lru lock contention after enable large folio for
anonymous mappping.

Running page_fault1 of will-it-scale + order 2 folio with 96
processes on Ice Lake 48C/96T, the lru lock contention could
be around 65%:
-   65.38%     0.17%  page_fault1_pro  [kernel.kallsyms]           [k]
    folio_lruvec_lock_irqsave
   - 65.21% folio_lruvec_lock_irqsave

With this patch, the lru lock contention dropped to 45% with same
testing:
-   44.93%     0.17%  page_fault1_pro  [kernel.kallsyms]           [k]
    folio_lruvec_lock_irqsave
   + 44.75% folio_lruvec_lock_irqsave

Signed-off-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
---
 include/linux/pagevec.h | 19 +++++++++++++++++--
 mm/swap.c               |  3 +--
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/include/linux/pagevec.h b/include/linux/pagevec.h
index f582f7213ea52..d719f7ad5a567 100644
--- a/include/linux/pagevec.h
+++ b/include/linux/pagevec.h
@@ -10,6 +10,7 @@
 #define _LINUX_PAGEVEC_H
 
 #include <linux/xarray.h>
+#include <linux/mm.h>
 
 /* 15 pointers + header align the pagevec structure to a power of two */
 #define PAGEVEC_SIZE	15
@@ -22,6 +23,7 @@ struct address_space;
 struct pagevec {
 	unsigned char nr;
 	bool percpu_pvec_drained;
+	unsigned short pages_nr;
 	struct page *pages[PAGEVEC_SIZE];
 };
 
@@ -30,6 +32,7 @@ void __pagevec_release(struct pagevec *pvec);
 static inline void pagevec_init(struct pagevec *pvec)
 {
 	pvec->nr = 0;
+	pvec->pages_nr = 0;
 	pvec->percpu_pvec_drained = false;
 }
 
@@ -54,7 +57,12 @@ static inline unsigned pagevec_space(struct pagevec *pvec)
 static inline unsigned pagevec_add(struct pagevec *pvec, struct page *page)
 {
 	pvec->pages[pvec->nr++] = page;
-	return pagevec_space(pvec);
+	pvec->pages_nr += compound_nr(page);
+
+	if (pvec->pages_nr > PAGEVEC_SIZE)
+		return 0;
+	else
+		return pagevec_space(pvec);
 }
 
 static inline void pagevec_release(struct pagevec *pvec)
@@ -75,6 +83,7 @@ static inline void pagevec_release(struct pagevec *pvec)
 struct folio_batch {
 	unsigned char nr;
 	bool percpu_pvec_drained;
+	unsigned short pages_nr;
 	struct folio *folios[PAGEVEC_SIZE];
 };
 
@@ -92,6 +101,7 @@ static_assert(offsetof(struct pagevec, pages) ==
 static inline void folio_batch_init(struct folio_batch *fbatch)
 {
 	fbatch->nr = 0;
+	fbatch->pages_nr = 0;
 	fbatch->percpu_pvec_drained = false;
 }
 
@@ -124,7 +134,12 @@ static inline unsigned folio_batch_add(struct folio_batch *fbatch,
 		struct folio *folio)
 {
 	fbatch->folios[fbatch->nr++] = folio;
-	return fbatch_space(fbatch);
+	fbatch->pages_nr += folio_nr_pages(folio);
+
+	if (fbatch->pages_nr > PAGEVEC_SIZE)
+		return 0;
+	else
+		return fbatch_space(fbatch);
 }
 
 static inline void folio_batch_release(struct folio_batch *fbatch)
diff --git a/mm/swap.c b/mm/swap.c
index 423199ee8478c..59e3f1e3701c3 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -228,8 +228,7 @@ static void folio_batch_move_lru(struct folio_batch *fbatch, move_fn_t move_fn)
 static void folio_batch_add_and_move(struct folio_batch *fbatch,
 		struct folio *folio, move_fn_t move_fn)
 {
-	if (folio_batch_add(fbatch, folio) && !folio_test_large(folio) &&
-	    !lru_cache_disabled())
+	if (folio_batch_add(fbatch, folio) && !lru_cache_disabled())
 		return;
 	folio_batch_move_lru(fbatch, move_fn);
 }
-- 
2.30.2