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[220.143.195.113]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2429b7dfc23sm29204985ad.105.2025.08.06.08.00.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Aug 2025 08:00:05 -0700 (PDT) From: "Adrian Huang (Lenovo)" To: Andrew Morton Cc: David Hildenbrand , Lorenzo Stoakes , Liam.Howlett@oracle.com, Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Feng Tang , ahuang12@lenovo.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Adrian Huang Subject: [PATCH v2 1/1] mm: Correct misleading comment on mmap_lock field in mm_struct Date: Wed, 6 Aug 2025 22:59:06 +0800 Message-Id: <20250806145906.24647-1-adrianhuang0701@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: B00C3C000F X-Stat-Signature: iyjkuh4mc3bst6fx9m67yy97kmehr4zm X-HE-Tag: 1754492407-598263 X-HE-Meta: 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 P8ijjtIl 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The comment previously described the offset of mmap_lock as 0x120 (hex), which is misleading. The correct offset is 56 bytes (decimal) from the last cache line boundary. Using '0x120' could confuse readers trying to understand why the count and owner fields reside in separate cachelines. This change also removes an unnecessary space for improved formatting. Signed-off-by: Adrian Huang (Lenovo) --- Changes in v2: Per Lorenzo's suggestion, use "56 bytes" instead of 120. include/linux/mm_types.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 1ec273b06691..c9c3d0307f8c 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1026,10 +1026,10 @@ struct mm_struct { * counters */ /* - * With some kernel config, the current mmap_lock's offset - * inside 'mm_struct' is at 0x120, which is very optimal, as + * Typically the current mmap_lock's offset is 56 bytes from + * the last cacheline boundary, which is very optimal, as * its two hot fields 'count' and 'owner' sit in 2 different - * cachelines, and when mmap_lock is highly contended, both + * cachelines, and when mmap_lock is highly contended, both * of the 2 fields will be accessed frequently, current layout * will help to reduce cache bouncing. * -- 2.34.1