netdev - [PATCH net-next 5/6] net: use synchronize_rcu_expedited in cleanup

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Date: Fri,  9 Feb 2024 15:31:00 +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: David Ahern <dsahern@...nel.org>, Pablo Neira Ayuso <pablo@...filter.org>, 
	Florian Westphal <fw@...len.de>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 5/6] net: use synchronize_rcu_expedited in cleanup_net()

cleanup_net() is calling synchronize_rcu() right before
acquiring RTNL.

synchronize_rcu() is much slower than synchronize_rcu_expedited(),
and cleanup_net() is currently single threaded. In many workloads
we want cleanup_net() to be fast, in order to free memory and various
sysfs and procfs entries as fast as possible.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/net_namespace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 233ec0cdd0111d5ca21c6f8a66f4c1f3fbc4657b..f0540c5575157135b1dc5dece2220f81a408fb7e 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -622,7 +622,7 @@ static void cleanup_net(struct work_struct *work)
 	 * the rcu_barrier() below isn't sufficient alone.
 	 * Also the pre_exit() and exit() methods need this barrier.
 	 */
-	synchronize_rcu();
+	synchronize_rcu_expedited();
 
 	rtnl_lock();
 	list_for_each_entry_reverse(ops, &pernet_list, list) {
-- 
2.43.0.687.g38aa6559b0-goog