linux-kernel - [PATCH v2 3/5] mm: swap_pte_batch: add an output argument to reture if all swap entries are exclusive

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Message-Id: <20240409082631.187483-4-21cnbao@gmail.com>
Date: Tue,  9 Apr 2024 20:26:29 +1200
From: Barry Song <21cnbao@...il.com>
To: akpm@...ux-foundation.org,
	linux-mm@...ck.org
Cc: baolin.wang@...ux.alibaba.com,
	chrisl@...nel.org,
	david@...hat.com,
	hanchuanhua@...o.com,
	hannes@...xchg.org,
	hughd@...gle.com,
	kasong@...cent.com,
	ryan.roberts@....com,
	surenb@...gle.com,
	v-songbaohua@...o.com,
	willy@...radead.org,
	xiang@...nel.org,
	ying.huang@...el.com,
	yosryahmed@...gle.com,
	yuzhao@...gle.com,
	ziy@...dia.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/5] mm: swap_pte_batch: add an output argument to reture if all swap entries are exclusive

From: Barry Song <v-songbaohua@...o.com>

Add a boolean argument named any_shared. If any of the swap entries are
non-exclusive, set any_shared to true. The function do_swap_page() can
then utilize this information to determine whether the entire large
folio can be reused.

Signed-off-by: Barry Song <v-songbaohua@...o.com>
---
 mm/internal.h | 9 ++++++++-
 mm/madvise.c  | 2 +-
 mm/memory.c   | 2 +-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 9d3250b4a08a..cae39c372bfc 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -238,7 +238,8 @@ static inline pte_t pte_next_swp_offset(pte_t pte)
  *
  * Return: the number of table entries in the batch.
  */
-static inline int swap_pte_batch(pte_t *start_ptep, int max_nr, pte_t pte)
+static inline int swap_pte_batch(pte_t *start_ptep, int max_nr, pte_t pte,
+				bool *any_shared)
 {
 	pte_t expected_pte = pte_next_swp_offset(pte);
 	const pte_t *end_ptep = start_ptep + max_nr;
@@ -248,12 +249,18 @@ static inline int swap_pte_batch(pte_t *start_ptep, int max_nr, pte_t pte)
 	VM_WARN_ON(!is_swap_pte(pte));
 	VM_WARN_ON(non_swap_entry(pte_to_swp_entry(pte)));
 
+	if (any_shared)
+		*any_shared |= !pte_swp_exclusive(pte);
+
 	while (ptep < end_ptep) {
 		pte = ptep_get(ptep);
 
 		if (!pte_same(pte, expected_pte))
 			break;
 
+		if (any_shared)
+			*any_shared |= !pte_swp_exclusive(pte);
+
 		expected_pte = pte_next_swp_offset(expected_pte);
 		ptep++;
 	}
diff --git a/mm/madvise.c b/mm/madvise.c
index f59169888b8e..d34ca6983227 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -671,7 +671,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 			entry = pte_to_swp_entry(ptent);
 			if (!non_swap_entry(entry)) {
 				max_nr = (end - addr) / PAGE_SIZE;
-				nr = swap_pte_batch(pte, max_nr, ptent);
+				nr = swap_pte_batch(pte, max_nr, ptent, NULL);
 				nr_swap -= nr;
 				free_swap_and_cache_nr(entry, nr);
 				clear_not_present_full_ptes(mm, addr, pte, nr, tlb->fullmm);
diff --git a/mm/memory.c b/mm/memory.c
index 2702d449880e..c4a52e8d740a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1638,7 +1638,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 			folio_put(folio);
 		} else if (!non_swap_entry(entry)) {
 			max_nr = (end - addr) / PAGE_SIZE;
-			nr = swap_pte_batch(pte, max_nr, ptent);
+			nr = swap_pte_batch(pte, max_nr, ptent, NULL);
 			/* Genuine swap entries, hence a private anon pages */
 			if (!should_zap_cows(details))
 				continue;
-- 
2.34.1