net: move netdev_max_backlog to net_hotdata

netdev_max_backlog is used in rx fat path.

Move it to net_hodata 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/20240306160031.874438-6-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/netdevice.h

@@ -4793,7 +4793,6 @@ void dev_fetch_sw_netstats(struct rtnl_link_stats64 *s,
 			   const struct pcpu_sw_netstats __percpu *netstats);
 void dev_get_tstats64(struct net_device *dev, struct rtnl_link_stats64 *s);
 
-extern int		netdev_max_backlog;
 extern int		dev_rx_weight;
 extern int		dev_tx_weight;
 

include/net/hotdata.h

@@ -12,6 +12,7 @@ struct net_hotdata {
 	int			netdev_budget;
 	int			netdev_budget_usecs;
 	int			tstamp_prequeue;
+	int			max_backlog;
 };
 
 extern struct net_hotdata net_hotdata;

net/core/dev.c

@@ -4404,9 +4404,6 @@ EXPORT_SYMBOL(__dev_direct_xmit);
  *			Receiver routines
  *************************************************************************/
 
-int netdev_max_backlog __read_mostly = 1000;
-EXPORT_SYMBOL(netdev_max_backlog);
-
 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 */
@@ -4713,7 +4710,7 @@ static bool skb_flow_limit(struct sk_buff *skb, unsigned int qlen)
 	struct softnet_data *sd;
 	unsigned int old_flow, new_flow;
 
-	if (qlen < (READ_ONCE(netdev_max_backlog) >> 1))
+	if (qlen < (READ_ONCE(net_hotdata.max_backlog) >> 1))
 		return false;
 
 	sd = this_cpu_ptr(&softnet_data);
@@ -4761,7 +4758,8 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
 	if (!netif_running(skb->dev))
 		goto drop;
 	qlen = skb_queue_len(&sd->input_pkt_queue);
-	if (qlen <= READ_ONCE(netdev_max_backlog) && !skb_flow_limit(skb, qlen)) {
+	if (qlen <= READ_ONCE(net_hotdata.max_backlog) &&
+	    !skb_flow_limit(skb, qlen)) {
 		if (qlen) {
 enqueue:
 			__skb_queue_tail(&sd->input_pkt_queue, skb);

net/core/gro_cells.c

@@ -3,6 +3,7 @@
 #include <linux/slab.h>
 #include <linux/netdevice.h>
 #include <net/gro_cells.h>
+#include <net/hotdata.h>
 
 struct gro_cell {
 	struct sk_buff_head	napi_skbs;
@@ -26,7 +27,7 @@ int gro_cells_receive(struct gro_cells *gcells, struct sk_buff *skb)
 
 	cell = this_cpu_ptr(gcells->cells);
 
-	if (skb_queue_len(&cell->napi_skbs) > READ_ONCE(netdev_max_backlog)) {
+	if (skb_queue_len(&cell->napi_skbs) > READ_ONCE(net_hotdata.max_backlog)) {
 drop:
 		dev_core_stats_rx_dropped_inc(dev);
 		kfree_skb(skb);

net/core/hotdata.c

@@ -15,4 +15,6 @@ struct net_hotdata net_hotdata __cacheline_aligned = {
 	.netdev_budget_usecs = 2 * USEC_PER_SEC / HZ,
 
 	.tstamp_prequeue = 1,
+	.max_backlog = 1000,
 };
+EXPORT_SYMBOL(net_hotdata);

net/core/sysctl_net_core.c

@@ -440,7 +440,7 @@ static struct ctl_table net_core_table[] = {
 	},
 	{
 		.procname	= "netdev_max_backlog",
-		.data		= &netdev_max_backlog,
+		.data		= &net_hotdata.max_backlog,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec

net/xfrm/espintcp.c

@@ -10,6 +10,7 @@
 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/ipv6_stubs.h>
 #endif
+#include <net/hotdata.h>
 
 static void handle_nonesp(struct espintcp_ctx *ctx, struct sk_buff *skb,
 			  struct sock *sk)
@@ -169,7 +170,8 @@ int espintcp_queue_out(struct sock *sk, struct sk_buff *skb)
 {
 	struct espintcp_ctx *ctx = espintcp_getctx(sk);
 
-	if (skb_queue_len(&ctx->out_queue) >= READ_ONCE(netdev_max_backlog))
+	if (skb_queue_len(&ctx->out_queue) >=
+	    READ_ONCE(net_hotdata.max_backlog))
 		return -ENOBUFS;
 
 	__skb_queue_tail(&ctx->out_queue, skb);

net/xfrm/xfrm_input.c

@@ -21,6 +21,7 @@
 #include <net/ip_tunnels.h>
 #include <net/ip6_tunnel.h>
 #include <net/dst_metadata.h>
+#include <net/hotdata.h>
 
 #include "xfrm_inout.h"
 
@@ -764,7 +765,7 @@ int xfrm_trans_queue_net(struct net *net, struct sk_buff *skb,
 
 	trans = this_cpu_ptr(&xfrm_trans_tasklet);
 
-	if (skb_queue_len(&trans->queue) >= READ_ONCE(netdev_max_backlog))
+	if (skb_queue_len(&trans->queue) >= READ_ONCE(net_hotdata.max_backlog))
 		return -ENOBUFS;
 
 	BUILD_BUG_ON(sizeof(struct xfrm_trans_cb) > sizeof(skb->cb));