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[v2,1/5] mm/memcontrol: Align percpu memcg_stock to cache

Message ID 20230125073502.743446-2-leobras@redhat.com (mailing list archive)
State New
Headers show
Series Introduce memcg_stock_pcp remote draining | expand

Commit Message

Leonardo Bras Jan. 25, 2023, 7:34 a.m. UTC 
When a struct smaller than a cacheline has an instance that is not aligned
to cache block size, it could happen that data can be spread across two
cachelines.

For memcg_stock this could mean the need to fetch and get cache-exclusivity
in 2 cachelines instead of 1 when we bounce the cacheline between local
cpu functions and drain_all_stock(), which does remote read/write.

This could also mean some false-sharing costs being paid due to the
cacheline being shared between 2 unrelated structures.

Avoid this issue by getting memcg_stock cacheline-aligned.

Signed-off-by: Leonardo Bras <leobras@redhat.com>
---
 mm/memcontrol.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ab457f0394ab6..f8e86b88b3c7a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2188,7 +2188,8 @@  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_SHARED_ALIGNED(struct memcg_stock_pcp, memcg_stock) = {
 	.stock_lock = INIT_LOCAL_LOCK(stock_lock),
 };
 static DEFINE_MUTEX(percpu_charge_mutex);