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Thu, 29 Oct 2026 22:52:44 -0700 (PDT) Received: from [127.0.1.1] ([23.254.208.9]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1ac1b0a628bsm3675448c88.22.2026.10.29.22.52.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Oct 2026 22:52:43 -0700 (PDT) From: Qiliang Yuan Date: Fri, 30 Oct 2026 01:52:38 -0400 Subject: [PATCH] mm/filemap: clear page cache marks once when removing a folio X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261030-bug-mm-filemap-init-marks-once-v1-1-699835fc6690@gmail.com> X-B4-Tracking: v=1; b=H4sIAKUw5GoC/x3NQQ5AMBBA0avIrE1SJCWuIhbTGkxoSYtIxN01l m/z/wORg3CENnsg8CVRNp9Q5BnYmfzEKEMylKrUhaoUmnNC53CUlR3tKF4OdBSWiJu3jKaprCb StSEDKbIHHuX+B13/vh+gfW5ecAAAAA== To: "Matthew Wilcox (Oracle)" , Jan Kara , Andrew Morton Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qiliang Yuan X-Mailer: b4 0.13.0 xas_store() clears the marks of an entry before it replaces the entry with NULL. page_cache_delete() calls xas_init_marks() after xas_store() whether it stored a shadow entry or NULL, so a folio removed without a shadow, as POSIX_FADV_DONTNEED and drop_caches do, has its marks cleared twice. With 4K folios that is about 6% of the time it takes to drop clean page cache. Call xas_init_marks() only after storing a shadow entry, whose marks xas_store() leaves alone. Dropping 8 GiB of 4K folios, median of five runs, averaged over two boots of each kernel, in a 32 vCPU VM: before after POSIX_FADV_DONTNEED 1517 ms 1423 ms drop_caches 1515 ms 1422 ms Signed-off-by: Qiliang Yuan --- mm/filemap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/filemap.c b/mm/filemap.c index b74bc1e5015c6..a0c959e74533e 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -140,7 +140,8 @@ static void page_cache_delete(struct address_space *mapping, VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); xas_store(&xas, shadow); - xas_init_marks(&xas); + if (shadow) + xas_init_marks(&xas); folio->mapping = NULL; /* Leave folio->index set: truncation lookup relies upon it */ --- base-commit: d89e1d186ec9271bf78e62771779e9fc03bf0fc3 change-id: 20261030-bug-mm-filemap-init-marks-once-b83c6aa67bab Best regards, -- Qiliang Yuan