net: move netdev_tstamp_prequeue into net_hotdata

netdev_tstamp_prequeue is used in rx path.

Move it to net_hotdata for better cache locality.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20240306160031.874438-4-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/hotdata.h

@@ -10,6 +10,7 @@ struct net_hotdata {
 	int			gro_normal_batch;
 	int			netdev_budget;
 	int			netdev_budget_usecs;
+	int			tstamp_prequeue;
 };
 
 extern struct net_hotdata net_hotdata;

net/core/dev.c

@@ -4408,7 +4408,6 @@ EXPORT_SYMBOL(__dev_direct_xmit);
 int netdev_max_backlog __read_mostly = 1000;
 EXPORT_SYMBOL(netdev_max_backlog);
 
-int netdev_tstamp_prequeue __read_mostly = 1;
 unsigned int sysctl_skb_defer_max __read_mostly = 64;
 int weight_p __read_mostly = 64;           /* old backlog weight */
 int dev_weight_rx_bias __read_mostly = 1;  /* bias for backlog weight */
@@ -5052,7 +5051,7 @@ static int netif_rx_internal(struct sk_buff *skb)
 {
 	int ret;
 
-	net_timestamp_check(READ_ONCE(netdev_tstamp_prequeue), skb);
+	net_timestamp_check(READ_ONCE(net_hotdata.tstamp_prequeue), skb);
 
 	trace_netif_rx(skb);
 
@@ -5344,7 +5343,7 @@ static int __netif_receive_skb_core(struct sk_buff **pskb, bool pfmemalloc,
 	int ret = NET_RX_DROP;
 	__be16 type;
 
-	net_timestamp_check(!READ_ONCE(netdev_tstamp_prequeue), skb);
+	net_timestamp_check(!READ_ONCE(net_hotdata.tstamp_prequeue), skb);
 
 	trace_netif_receive_skb(skb);
 
@@ -5728,7 +5727,7 @@ static int netif_receive_skb_internal(struct sk_buff *skb)
 {
 	int ret;
 
-	net_timestamp_check(READ_ONCE(netdev_tstamp_prequeue), skb);
+	net_timestamp_check(READ_ONCE(net_hotdata.tstamp_prequeue), skb);
 
 	if (skb_defer_rx_timestamp(skb))
 		return NET_RX_SUCCESS;
@@ -5758,7 +5757,8 @@ void netif_receive_skb_list_internal(struct list_head *head)
 
 	INIT_LIST_HEAD(&sublist);
 	list_for_each_entry_safe(skb, next, head, list) {
-		net_timestamp_check(READ_ONCE(netdev_tstamp_prequeue), skb);
+		net_timestamp_check(READ_ONCE(net_hotdata.tstamp_prequeue),
+				    skb);
 		skb_list_del_init(skb);
 		if (!skb_defer_rx_timestamp(skb))
 			list_add_tail(&skb->list, &sublist);

net/core/dev.h

@@ -39,7 +39,6 @@ void dev_addr_check(struct net_device *dev);
 
 /* sysctls not referred to from outside net/core/ */
 extern unsigned int	sysctl_skb_defer_max;
-extern int		netdev_tstamp_prequeue;
 extern int		netdev_unregister_timeout_secs;
 extern int		weight_p;
 extern int		dev_weight_rx_bias;

net/core/hotdata.c

@@ -12,4 +12,6 @@ struct net_hotdata net_hotdata __cacheline_aligned = {
 	.netdev_budget = 300,
 	/* Must be at least 2 jiffes to guarantee 1 jiffy timeout */
 	.netdev_budget_usecs = 2 * USEC_PER_SEC / HZ,
+
+	.tstamp_prequeue = 1,
 };

net/core/sysctl_net_core.c

@@ -499,7 +499,7 @@ static struct ctl_table net_core_table[] = {
 #endif
 	{
 		.procname	= "netdev_tstamp_prequeue",
-		.data		= &netdev_tstamp_prequeue,
+		.data		= &net_hotdata.tstamp_prequeue,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec