From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792425052; b=l3pAIsADRaJNSo/qB0RsF5QrHIqIEb1JqJAs4oe2cT0lfqtIEXVWHjIwQZrOyZ8kjoOL ZYdZimg3O9Ck6cXvMn2OZt4NNsON1TsjCEwOonhGe4FyaUQq3b4DiTA0qPK+JB+3rp86A yjuPOUPVNtIKPMPLy90cj6DnJAcR0aHxjbVYoB22bAUtrj2WNqVCG2kd2noHEpFAtc0CV nLR4EZS3TBjNY/hu3rUzi05lbPJqKwgGqy/TzKjT6xMuQnPs9yLj20udNntMa8CArUjBz gsE/Q2noL1NlVB/cVxdcK97f4C8EGu9+Z2WxJWmhZ6kraj0Rsh1AmrO1NglGi9+ZR9Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792425052; h=Received:DKIM-Signature:Received:Received:X-ME-Sender:X-ME-Received: X-ME-Proxy-Cause:X-ME-Proxy:Feedback-ID:Received:From:To:Cc:Subject: Date:Message-ID:X-Mailer:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding; bh=1tklyEFR6gzCJ5Mm0LyngFaJuzsqMluVwnmmNtY4Bjo=; b=v73jvIUIZXRVwhOrW4gEYjMw5F0ojJCHmXs9DuIt/s9ByAkzu0pkwo0mk9A7Ndnb2Kdm MNgfXnZNxJQBe/nrCzO8Wj1PE6EBkg9HFPJJMvc1T4IXRI9N9NZdPA3mur7DNmCrT/9sc F/xx9WEVWN376Ar3d3BvZl2KlcRYsM5TKiTp9Eq2BSW9am7xVF5tXNY1++9f2Ie0fWjKj UCb2VinEl8pWV8SEQneZmkxUGhuge0AwKx7YniYDP2N4N4XpwQFL7nEsKXdNThn/iYv9O Z+Yi/S8bqne7N8oBCYU5DSIb6866mmT3pYCSjLD307dMHeNxbBqAcUjEYDbJXtgi57Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=hsXIhuWW; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7DE7C606AAE8; Mon, 19 Oct 2026 15:50:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=hsXIhuWW Received: by smtp.kernel.org (Postfix) with ESMTPSA id 621B01F000CB; Mon, 19 Oct 2026 15:50:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792425051; bh=1tklyEFR6gzCJ5Mm0LyngFaJuzsqMluVwnmmNtY4Bjo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=hsXIhuWW5cj0PTnvYiQiB6X2pHdnoes0T9srZXVcGrGCLignDLmHgupnUcoAgQ6sL zNEpP2bzdCxqRAzHHta6tZqeBuB/Ybnq7NpmSLKcyxol4ZNb5HZjMVH3Fi6HN2lIa8 RT6361ta0KFbAm1A7d4ohT1mxTZGqmPad99jfEOBeVsQPuMb5cqHMTV/F1S2gNpWn9 36gbsPRKMmo/fkjzpLprlWSRnqpI4UNcBnFS2ZcF2CKMRpSARaxRs88W2d25DKTwpP bYwnV06hz7rhXb4KqmlQ97hCoZQGDTLCKj1DWLvkR47g5T1eFJyfX3ZzR4maur/kXM c/oH0GAq61XAg== Received: from phl-compute-05.internal (phl-compute-05.internal [10.202.2.45]) by mailfauth.ams.internal (Postfix) with ESMTP id 4FBAE1980047; Mon, 19 Oct 2026 11:50:43 -0400 (EDT) Received: from phl-frontend-04 ([10.202.2.163]) by phl-compute-05.internal (MEProxy); Mon, 19 Oct 2026 11:50:47 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: dmFkZTEfcY8Sedpzpe5Eju9n5oayhWKPyUV/WN4ORzd354gnHcUNRyDxnfDrVtF0Alji6y FwZ4Dnqmp2xFA5TRzvzZXvYk9IWIcIACK0GXlQFj7v3uEIoT3YE0GAecfgycvJObnsWgyU omy/lOe9Ul2f7WNFeSYzOhn9Xhyn3eRZ1/u1NlpfN8iOBPXkq7lLkPZY3eLvZtE4xL/1Z+ 12+yKL0HGegFnoIlCDAqs/SztneWlDn0ZvTxx6bOoXiDCEows+EqK1vqCcT2wFPXdzHPq0 s7OKMwp4WgMV4JhSm776pUXmDzbWh34FJ6orb+IJbBIpKyqJoy5T7ZZsX3UOdwDn/V3zkn ciLaL3SK5aczqSEptHZ258YgE9enzFCIUpka6iwuWD4uOZeMrkBJzpGIh4KYoSTKKtrZvs 4xlScy5Hvhm0g7xX4aojdn8ZeOHImmKyG4/X0NM0BEhBJZwbtMoljvktLExWcSAkjo8TeY M9ZgiJ4yApWw5S7yHaoM4S1qhuWXr76hmoCzlz/14P2STYv2JmsxWXbP8qgk3L+yEEfm4+ 3MerERvzt9ihX2Y+062QX7gG/Ixr1M6EPT/QUzWtcZAGVChJyuJxYkvUbIu8P8Xs/1zdh2 jr3zr60rV2eRRKH1RKef8o1ShHXZiOm4tHdbt5LbIl8o+Sy3moybVLTrAMFg X-ME-Proxy: Feedback-ID: i10464835:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Mon, 19 Oct 2026 11:50:41 -0400 (EDT) From: "Kiryl Shutsemau (Meta)" To: Andrew Morton , Linus Torvalds , David Hildenbrand , Matthew Wilcox , Vlastimil Babka , Lorenzo Stoakes , Jan Kara , Hugh Dickins , Christian Brauner , Alexander Viro Cc: "Kiryl Shutsemau (Meta)" , Miklos Szeredi , Miaohe Lin , Naoya Horiguchi , Oscar Salvador , "Liam R . Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kairui Song , Qi Zheng , Shakeel Butt , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , "Paul E . McKenney" , Pedro Falcato , Harry Yoo , Luis Chamberlain , Ilya Gladyshev , Jaegeuk Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, fuse-devel@lists.linux.dev, kernel-team@meta.com Subject: [RFC PATCH 13/18] mm/filemap: store the end of a read in f_ra only when it changes Date: Mon, 19 Oct 2026 16:49:06 +0100 Message-ID: <20261019154913.1765974-14-kas@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20261019154913.1765974-1-kas@kernel.org> References: <20261019154913.1765974-1-kas@kernel.org> 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-Transfer-Encoding: 8bit filemap_read() writes the end of every read to file->f_ra.prev_pos. Threads that read through one open file all write that cache line, on every read. The value often stays the same, as for reads that start at the same offset each time. Store it only when it changes. Assisted-by: LLM Signed-off-by: Kiryl Shutsemau (Meta) --- mm/filemap.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/filemap.c b/mm/filemap.c index 53ec92279977..960d53b61d4b 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2941,7 +2941,9 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter, } while (iov_iter_count(iter) && iocb->ki_pos < isize && !error); file_accessed(filp); - ra->prev_pos = last_pos; + /* Readers sharing the file would bounce the line for nothing */ + if (ra->prev_pos != last_pos) + ra->prev_pos = last_pos; return already_read ? already_read : error; } EXPORT_SYMBOL_GPL(filemap_read); -- 2.54.0