netdev - [PATCH v2 net-next 12/14] net: move napi

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Date:	Wed, 18 Nov 2015 06:31:01 -0800
From:	Eric Dumazet <edumazet@...gle.com>
To:	"David S . Miller" <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	Eliezer Tamir <eliezer.tamir@...ux.intel.com>,
	Eli Cohen <eli@...lanox.com>,
	Eugenia Emantayev <eugenia@...lanox.com>,
	Ariel Elior <ariel.elior@...gic.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Rida Assaf <rida@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH v2 net-next 12/14] net: move napi_hash[] into read mostly section

We do not often add/delete a napi context.
Moving napi_hash[] into read mostly section avoids potential false sharing.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/linux/hashtable.h | 4 ++++
 net/core/dev.c            | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/linux/hashtable.h b/include/linux/hashtable.h
index 519b6e2d769e..661e5c2a8e2a 100644
--- a/include/linux/hashtable.h
+++ b/include/linux/hashtable.h
@@ -16,6 +16,10 @@
 	struct hlist_head name[1 << (bits)] =					\
 			{ [0 ... ((1 << (bits)) - 1)] = HLIST_HEAD_INIT }
 
+#define DEFINE_READ_MOSTLY_HASHTABLE(name, bits)				\
+	struct hlist_head name[1 << (bits)] __read_mostly =			\
+			{ [0 ... ((1 << (bits)) - 1)] = HLIST_HEAD_INIT }
+
 #define DECLARE_HASHTABLE(name, bits)                                   	\
 	struct hlist_head name[1 << (bits)]
 
diff --git a/net/core/dev.c b/net/core/dev.c
index ff58a8bc5e3c..02dfbd91a8e4 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -184,7 +184,7 @@ EXPORT_SYMBOL(dev_base_lock);
 static DEFINE_SPINLOCK(napi_hash_lock);
 
 static unsigned int napi_gen_id = NR_CPUS;
-static DEFINE_HASHTABLE(napi_hash, 8);
+static DEFINE_READ_MOSTLY_HASHTABLE(napi_hash, 8);
 
 static seqcount_t devnet_rename_seq;
 
-- 
2.6.0.rc2.230.g3dd15c0

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