netdev - [PATCH net-next 4/5] net: make napi_threaded_poll() aware of sd->defer

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Date:   Fri, 21 Apr 2023 09:43:56 +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:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 4/5] net: make napi_threaded_poll() aware of sd->defer_list

If we call skb_defer_free_flush() from napi_threaded_poll(),
we can avoid to raise IPI from skb_attempt_defer_free()
when the list becomes too big.

This allows napi_threaded_poll() to rely less on softirqs,
and lowers latency caused by a too big list.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/dev.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 81ded215731bdbb3a025fe40ed9638123d97a347..7d9ec23f97c6ec80ec9f971f740a9da747f78ceb 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6622,6 +6622,7 @@ static void skb_defer_free_flush(struct softnet_data *sd)
 static int napi_threaded_poll(void *data)
 {
 	struct napi_struct *napi = data;
+	struct softnet_data *sd;
 	void *have;
 
 	while (!napi_thread_wait(napi)) {
@@ -6629,11 +6630,13 @@ static int napi_threaded_poll(void *data)
 			bool repoll = false;
 
 			local_bh_disable();
+			sd = this_cpu_ptr(&softnet_data);
 
 			have = netpoll_poll_lock(napi);
 			__napi_poll(napi, &repoll);
 			netpoll_poll_unlock(have);
 
+			skb_defer_free_flush(sd);
 			local_bh_enable();
 
 			if (!repoll)
-- 
2.40.0.634.g4ca3ef3211-goog