Commit 6df13230 authored Jul 01, 2024 by Roman Gushchin Committed by Andrew Morton Jul 10, 2024

mm: memcg: add cache line padding to mem_cgroup_per_node

Memcg v1-specific fields serve a buffer function between read-mostly and
update often parts of the mem_cgroup_per_node structure.  If
CONFIG_MEMCG_V1 is not set and these fields are not present, an explicit
cacheline padding is needed.

Link: https://lkml.kernel.org/r/20240701185932.704807-2-roman.gushchin@linux.dev


Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Suggested-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 9fa001cf

include/linux/memcontrol.h

+4 −2

Original line number	Diff line number	Diff line
		@@ -95,14 +95,16 @@ struct mem_cgroup_per_node {
		#ifdef CONFIG_MEMCG_V1
		/*
		* Memcg-v1 only stuff in middle as buffer between read mostly fields
		* and update often fields to avoid false sharing. Once v1 stuff is
		* moved in a separate struct, an explicit padding is needed.
		* and update often fields to avoid false sharing. If v1 stuff is
		* not present, an explicit padding is needed.
		*/

		struct rb_node tree_node; /* RB tree node */
		unsigned long usage_in_excess;/* Set to the value by which */
		/* the soft limit is exceeded*/
		bool on_tree;
		#else
		CACHELINE_PADDING(_pad1_);
		#endif

		/* Fields which get updated often at the end. */