netdev - [PATCH net-next 1/4] net: add struct net_aligned

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Message-ID: <20250627200551.348096-2-edumazet@google.com>
Date: Fri, 27 Jun 2025 20:05:48 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 1/4] net: add struct net_aligned_data

This structure will hold networking data that must
consume a full cache line to avoid accidental false sharing.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/aligned_data.h | 16 ++++++++++++++++
 net/core/hotdata.c         |  3 +++
 2 files changed, 19 insertions(+)
 create mode 100644 include/net/aligned_data.h

diff --git a/include/net/aligned_data.h b/include/net/aligned_data.h
new file mode 100644
index 0000000000000000000000000000000000000000..cf3329d7c2272ec4424e89352626800cbc282663
--- /dev/null
+++ b/include/net/aligned_data.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _NET_ALIGNED_DATA_H
+#define _NET_ALIGNED_DATA_H
+
+#include <linux/types.h>
+
+/* Structure holding cacheline aligned fields on SMP builds.
+ * Each field or group should have an ____cacheline_aligned_in_smp
+ * attribute to ensure no accidental false sharing can happen.
+ */
+struct net_aligned_data {
+};
+
+extern struct net_aligned_data net_aligned_data;
+
+#endif /* _NET_ALIGNED_DATA_H */
diff --git a/net/core/hotdata.c b/net/core/hotdata.c
index 0bc893d5f07b03b31e08967a2238f63d218020d7..e9c03491ab001cc85fd60ad28533649b32d8a003 100644
--- a/net/core/hotdata.c
+++ b/net/core/hotdata.c
@@ -2,6 +2,7 @@
 #include <linux/cache.h>
 #include <linux/jiffies.h>
 #include <linux/list.h>
+#include <net/aligned_data.h>
 #include <net/hotdata.h>
 #include <net/proto_memory.h>
 
@@ -22,3 +23,5 @@ struct net_hotdata net_hotdata __cacheline_aligned = {
 	.sysctl_mem_pcpu_rsv = SK_MEMORY_PCPU_RESERVE
 };
 EXPORT_SYMBOL(net_hotdata);
+
+struct net_aligned_data net_aligned_data;
-- 
2.50.0.727.gbf7dc18ff4-goog