linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: "Adrian Huang (Lenovo)" <adrianhuang0701@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@redhat.com>,
	Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
	Liam.Howlett@oracle.com, Vlastimil Babka <vbabka@suse.cz>,
	Mike Rapoport <rppt@kernel.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Michal Hocko <mhocko@suse.com>,
	Feng Tang <feng.79.tang@gmail.com>,
	ahuang12@lenovo.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org,
	Adrian Huang <adrianhuang0701@gmail.com>
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	[thread overview]
Message-ID: <20250806145906.24647-1-adrianhuang0701@gmail.com> (raw)

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) <adrianhuang0701@gmail.com>
---
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



             reply	other threads:[~2025-08-06 15:00 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-08-06 14:59 Adrian Huang (Lenovo) [this message]
2025-08-06 19:07 ` [PATCH v2 1/1] mm: Correct misleading comment on mmap_lock field in mm_struct Lorenzo Stoakes
2025-08-06 20:06   ` David Hildenbrand

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20250806145906.24647-1-adrianhuang0701@gmail.com \
    --to=adrianhuang0701@gmail.com \
    --cc=Liam.Howlett@oracle.com \
    --cc=ahuang12@lenovo.com \
    --cc=akpm@linux-foundation.org \
    --cc=david@redhat.com \
    --cc=feng.79.tang@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=lorenzo.stoakes@oracle.com \
    --cc=mhocko@suse.com \
    --cc=rppt@kernel.org \
    --cc=surenb@google.com \
    --cc=vbabka@suse.cz \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).