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From:   cgel.zte@gmail.com
To:     akpm@linux-foundation.org, bsingharora@gmail.com
Cc:     corbet@lwn.net, willy@infradead.org, yang.yang29@zte.com.cn,
        david@redhat.com, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, CGEL ZTE <cgel.zte@gmail.com>
Subject: [PATCH] filemap: Make the accounting of thrashing more consistent
Date:   Fri,  5 Aug 2022 03:38:39 +0000
Message-Id: <20220805033838.1714674-1-yang.yang29@zte.com.cn>
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From: Yang Yang <yang.yang29@zte.com.cn>

Once upon a time, we only support accounting thrashing of page cache.
Then Joonsoo introduced workingset detection for anonymous pages and
we gained the ability to account thrashing of them[1].

So let delayacct account both the thrashing of page cache and anonymous
pages, this could make the codes more consistent and simpler.

[1] commit aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU")

Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: CGEL ZTE <cgel.zte@gmail.com>
---
 Documentation/accounting/delay-accounting.rst |  2 +-
 mm/filemap.c                                  | 18 ++++--------------
 2 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/Documentation/accounting/delay-accounting.rst b/Documentation/accounting/delay-accounting.rst
index 241d1a87f2cd..7103b62ba6d7 100644
--- a/Documentation/accounting/delay-accounting.rst
+++ b/Documentation/accounting/delay-accounting.rst
@@ -13,7 +13,7 @@ a) waiting for a CPU (while being runnable)
 b) completion of synchronous block I/O initiated by the task
 c) swapping in pages
 d) memory reclaim
-e) thrashing page cache
+e) thrashing
 f) direct compact
 g) write-protect copy
 
diff --git a/mm/filemap.c b/mm/filemap.c
index 15800334147b..cfe15e89b3c2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1221,15 +1221,11 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
 	struct wait_page_queue wait_page;
 	wait_queue_entry_t *wait = &wait_page.wait;
 	bool thrashing = false;
-	bool delayacct = false;
 	unsigned long pflags;
 
 	if (bit_nr == PG_locked &&
 	    !folio_test_uptodate(folio) && folio_test_workingset(folio)) {
-		if (!folio_test_swapbacked(folio)) {
-			delayacct_thrashing_start();
-			delayacct = true;
-		}
+		delayacct_thrashing_start();
 		psi_memstall_enter(&pflags);
 		thrashing = true;
 	}
@@ -1329,8 +1325,7 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
 	finish_wait(q, wait);
 
 	if (thrashing) {
-		if (delayacct)
-			delayacct_thrashing_end();
+		delayacct_thrashing_end();
 		psi_memstall_leave(&pflags);
 	}
 
@@ -1378,17 +1373,13 @@ void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
 	struct wait_page_queue wait_page;
 	wait_queue_entry_t *wait = &wait_page.wait;
 	bool thrashing = false;
-	bool delayacct = false;
 	unsigned long pflags;
 	wait_queue_head_t *q;
 	struct folio *folio = page_folio(pfn_swap_entry_to_page(entry));
 
 	q = folio_waitqueue(folio);
 	if (!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
-		if (!folio_test_swapbacked(folio)) {
-			delayacct_thrashing_start();
-			delayacct = true;
-		}
+		delayacct_thrashing_start();
 		psi_memstall_enter(&pflags);
 		thrashing = true;
 	}
@@ -1435,8 +1426,7 @@ void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
 	finish_wait(q, wait);
 
 	if (thrashing) {
-		if (delayacct)
-			delayacct_thrashing_end();
+		delayacct_thrashing_end();
 		psi_memstall_leave(&pflags);
 	}
 }
-- 
2.25.1