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@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 5 insertions, 1 deletions

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;