netdev - Re: [PATCH] memcg: multi-memcg percpu charge cache

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Message-ID: <dieeei3squ2gcnqxdjayvxbvzldr266rhnvtl3vjzsqevxkevf@ckui5vjzl2qg>
Date: Wed, 30 Apr 2025 08:32:42 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Muchun Song <muchun.song@...ux.dev>, 
	Vlastimil Babka <vbabka@...e.cz>, Jakub Kicinski <kuba@...nel.org>, 
	Eric Dumazet <edumazet@...gle.com>, Soheil Hassas Yeganeh <soheil@...gle.com>, linux-mm@...ck.org, 
	cgroups@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH] memcg: multi-memcg percpu charge cache

Andrew, please find another fix/improvements for this patch below.

From: Shakeel Butt <shakeel.butt@...ux.dev>
Date: Wed, 30 Apr 2025 08:28:23 -0700
Subject: [PATCH] memcg: multi-memcg percpu charge cache - fix 4

Add comment suggested by Michal and use DEFINE_PER_CPU_ALIGNED instead
of DEFINE_PER_CPU suggested by Vlastimil.

Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
---
 mm/memcontrol.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5a07e0375254..b877287aeb11 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1775,6 +1775,10 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg)
 	pr_cont(" are going to be killed due to memory.oom.group set\n");
 }
 
+/*
+ * The value of NR_MEMCG_STOCK is selected to keep the cached memcgs and their
+ * nr_pages in a single cacheline. This may change in future.
+ */
 #define NR_MEMCG_STOCK 7
 struct memcg_stock_pcp {
 	local_trylock_t stock_lock;
@@ -1791,7 +1795,7 @@ struct memcg_stock_pcp {
 	unsigned long flags;
 #define FLUSHING_CACHED_CHARGE	0
 };
-static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock) = {
+static DEFINE_PER_CPU_ALIGNED(struct memcg_stock_pcp, memcg_stock) = {
 	.stock_lock = INIT_LOCAL_TRYLOCK(stock_lock),
 };
 static DEFINE_MUTEX(percpu_charge_mutex);
-- 
2.47.1