The patch titled
Subject: page_counter: reduce struct page_counter size
has been added to the -mm mm-unstable branch. Its filename is
page_counter-reduce-struct-page_counter-size.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/page_counter-reduce-struct-page_counter-size.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Subject: page_counter: reduce struct page_counter size
Date: Thu, 27 Feb 2025 23:58:08 -0800
The struct page_counter has explicit padding for better cache alignment.
The commit c6f53ed8f213a ("mm, memcg: cg2 memory{.swap,}.peak write
handlers") added a field to the struct page_counter and accidently
increased its size. Let's move the failcnt field which is v1-only field
to the same cacheline of usage to reduce the size of struct page_counter.
Link: https://lkml.kernel.org/r/20250228075808.207484-4-shakeel.butt@xxxxxxxxx
Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Roman Gushchin (Cruise) <roman.gushchin@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/page_counter.h | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--- a/include/linux/page_counter.h~page_counter-reduce-struct-page_counter-size
+++ a/include/linux/page_counter.h
@@ -9,10 +9,12 @@
struct page_counter {
/*
- * Make sure 'usage' does not share cacheline with any other field. The
- * memcg->memory.usage is a hot member of struct mem_cgroup.
+ * Make sure 'usage' does not share cacheline with any other field in
+ * v2. The memcg->memory.usage is a hot member of struct mem_cgroup.
*/
atomic_long_t usage;
+ unsigned long failcnt; /* v1-only field */
+
CACHELINE_PADDING(_pad1_);
/* effective memory.min and memory.min usage tracking */
@@ -28,7 +30,6 @@ struct page_counter {
unsigned long watermark;
/* Latest cg2 reset watermark */
unsigned long local_watermark;
- unsigned long failcnt; /* v1-only field */
/* Keep all the read most fields in a separete cacheline. */
CACHELINE_PADDING(_pad2_);
_
Patches currently in -mm which might be from shakeel.butt@xxxxxxxxx are
memcg-add-hierarchical-effective-limits-for-v2.patch
memcg-dont-call-propagate_protected_usage-for-v1.patch
page_counter-track-failcnt-only-for-legacy-cgroups.patch
page_counter-reduce-struct-page_counter-size.patch
