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page_counter: reduce struct page_counter size

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The struct page_counter has explicit padding for better cache alignment. 
The commit c6f53ed8f2 ("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@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Shakeel Butt
2025-03-17 00:05:36 -07:00
committed by Andrew Morton
parent 0e2759afca
commit f7b0797d36
1 changed files with 4 additions and 3 deletions
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include/linux/page_counter.h
+4 -3
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@@ -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_);