linux-kernel - [RFC PATCH 1/1] mm: mark folio accessed in minor fault

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Date: Wed, 20 Dec 2023 18:29:48 +0800
From: "zhaoyang.huang" <zhaoyang.huang@...soc.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox
	<willy@...radead.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        Zhaoyang Huang <huangzhaoyang@...il.com>, <steve.kang@...soc.com>
Subject: [RFC PATCH 1/1] mm: mark folio accessed in minor fault

From: Zhaoyang Huang <zhaoyang.huang@...soc.com>

Inactive mapped folio will be promoted to active only when it is
scanned in shrink_inactive_list, while the vfs folio will do this
immidiatly when it is accessed. These will introduce two affections:

1. NR_ACTIVE_FILE is not accurate as expected.
2. Low reclaiming efficiency caused by dummy nactive folio which should
   be kept as earlier as shrink_active_list.

I would like to suggest mark the folio be accessed in minor fault to
solve this situation.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
---
 mm/filemap.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index f0a15ce1bd1b..b1ee6ce716c2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3273,6 +3273,11 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
 	 */
 	folio = filemap_get_folio(mapping, index);
 	if (likely(!IS_ERR(folio))) {
+		/*
+		 * try to promote inactive folio here when it is accessed
+		 * as minor fault
+		 */
+		folio_mark_accessed(folio);
 		/*
 		 * We found the page, so try async readahead before waiting for
 		 * the lock.
-- 
2.25.1