Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 588f0330 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: use jump_label for netstamp_needed 



netstamp_needed seems a good candidate to jump_label conversion.

This avoids 3 conditional branches per incoming packet in fast path.

No measurable difference, given that these conditional branches are
predicted on modern cpus. Only a small icache reduction, thanks to the
unlikely() stuff.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 66846048

net/core/dev.c

+14 −18
Original line number Diff line number Diff line
@@ -137,6 +137,7 @@ 
#include <linux/if_pppox.h>

#include <linux/ppp_defs.h>

#include <linux/net_tstamp.h>

#include <linux/jump_label.h>



#include "net-sysfs.h"
@@ -1449,35 +1450,33 @@ int call_netdevice_notifiers(unsigned long val, struct net_device *dev) 
}

EXPORT_SYMBOL(call_netdevice_notifiers);



/* When > 0 there are consumers of rx skb time stamps */

static atomic_t netstamp_needed = ATOMIC_INIT(0);

static struct jump_label_key netstamp_needed __read_mostly;



void net_enable_timestamp(void)

{

	atomic_inc(&netstamp_needed);

	jump_label_inc(&netstamp_needed);

}

EXPORT_SYMBOL(net_enable_timestamp);



void net_disable_timestamp(void)

{

	atomic_dec(&netstamp_needed);

	jump_label_dec(&netstamp_needed);

}

EXPORT_SYMBOL(net_disable_timestamp);



static inline void net_timestamp_set(struct sk_buff *skb)

{

	if (atomic_read(&netstamp_needed))

		__net_timestamp(skb);

	else

	skb->tstamp.tv64 = 0;

}



static inline void net_timestamp_check(struct sk_buff *skb)

{

	if (!skb->tstamp.tv64 && atomic_read(&netstamp_needed))

	if (static_branch(&netstamp_needed))

		__net_timestamp(skb);

}



#define net_timestamp_check(COND, SKB)			\

	if (static_branch(&netstamp_needed)) {		\

		if ((COND) && !(SKB)->tstamp.tv64)	\

			__net_timestamp(SKB);		\

	}						\



static int net_hwtstamp_validate(struct ifreq *ifr)

{

	struct hwtstamp_config cfg;
@@ -2997,8 +2996,7 @@ int netif_rx(struct sk_buff *skb) 
	if (netpoll_rx(skb))

		return NET_RX_DROP;



	if (netdev_tstamp_prequeue)

		net_timestamp_check(skb);

	net_timestamp_check(netdev_tstamp_prequeue, skb);



	trace_netif_rx(skb);

#ifdef CONFIG_RPS
@@ -3230,8 +3228,7 @@ static int __netif_receive_skb(struct sk_buff *skb) 
	int ret = NET_RX_DROP;

	__be16 type;



	if (!netdev_tstamp_prequeue)

		net_timestamp_check(skb);

	net_timestamp_check(!netdev_tstamp_prequeue, skb);



	trace_netif_receive_skb(skb);
@@ -3362,8 +3359,7 @@ static int __netif_receive_skb(struct sk_buff *skb) 
 */

int netif_receive_skb(struct sk_buff *skb)

{

	if (netdev_tstamp_prequeue)

		net_timestamp_check(skb);

	net_timestamp_check(netdev_tstamp_prequeue, skb);



	if (skb_defer_rx_timestamp(skb))

		return NET_RX_SUCCESS;