netdev - [PATCH net-next 2/4] net: add softnet_data.in_net_rx

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Date:   Tue, 28 Mar 2023 23:50:19 +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:     Jason Xing <kernelxing@...cent.com>, netdev@...r.kernel.org,
        eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 2/4] net: add softnet_data.in_net_rx_action

We want to make two optimizations in napi_schedule_rps() and
____napi_schedule() which require to know if these helpers are
called from net_rx_action(), instead of being called from
other contexts.

sd.in_net_rx_action is only read/written by the owning cpu.

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

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 18a5be6ddd0f7c1a7b8169440808bc66c991d8de..c8c634091a65966fee661695d34ba8a7cf2cd8e7 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3188,6 +3188,7 @@ struct softnet_data {
 #ifdef CONFIG_RPS
 	struct softnet_data	*rps_ipi_list;
 #endif
+	bool			in_net_rx_action;
 #ifdef CONFIG_NET_FLOW_LIMIT
 	struct sd_flow_limit __rcu *flow_limit;
 #endif
diff --git a/net/core/dev.c b/net/core/dev.c
index f7050b95d125014d00f4c876175b1569d82525cd..15331edbacf4ca59aa5772c29e95cacd3c106e3f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6646,6 +6646,7 @@ static __latent_entropy void net_rx_action(struct softirq_action *h)
 	LIST_HEAD(list);
 	LIST_HEAD(repoll);
 
+	sd->in_net_rx_action = true;
 	local_irq_disable();
 	list_splice_init(&sd->poll_list, &list);
 	local_irq_enable();
@@ -6656,6 +6657,7 @@ static __latent_entropy void net_rx_action(struct softirq_action *h)
 		skb_defer_free_flush(sd);
 
 		if (list_empty(&list)) {
+			sd->in_net_rx_action = false;
 			if (!sd_has_rps_ipi_waiting(sd) && list_empty(&repoll))
 				goto end;
 			break;
@@ -6682,6 +6684,8 @@ static __latent_entropy void net_rx_action(struct softirq_action *h)
 	list_splice(&list, &sd->poll_list);
 	if (!list_empty(&sd->poll_list))
 		__raise_softirq_irqoff(NET_RX_SOFTIRQ);
+	else
+		sd->in_net_rx_action = false;
 
 	net_rps_action_and_irq_enable(sd);
 end:;
-- 
2.40.0.348.gf938b09366-goog