Commit 5175c378 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

[NET]: reduce per cpu ram used for loopback stats 



We dont need a full struct net_device_stats (currently 23 long : 184 bytes on 
x86_64) per possible CPU, but only two counters : bytes and packets

We save few CPU cycles too in loopback_xmit() not updating 4 fields, but 2. 

Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9ce8ade0

drivers/net/loopback.c

+19 −16
Original line number Diff line number Diff line
@@ -58,7 +58,11 @@ 
#include <linux/tcp.h>

#include <linux/percpu.h>



static DEFINE_PER_CPU(struct net_device_stats, loopback_stats);

struct pcpu_lstats {

	unsigned long packets;

	unsigned long bytes;

};

static DEFINE_PER_CPU(struct pcpu_lstats, pcpu_lstats);



#define LOOPBACK_OVERHEAD (128 + MAX_HEADER + 16 + 16)
@@ -128,7 +132,7 @@ static void emulate_large_send_offload(struct sk_buff *skb) 
 */

static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)

{

	struct net_device_stats *lb_stats;

	struct pcpu_lstats *lb_stats;



	skb_orphan(skb);
@@ -149,11 +153,9 @@ static int loopback_xmit(struct sk_buff *skb, struct net_device *dev) 
#endif

	dev->last_rx = jiffies;



	lb_stats = &per_cpu(loopback_stats, get_cpu());

	lb_stats->rx_bytes += skb->len;

	lb_stats->tx_bytes = lb_stats->rx_bytes;

	lb_stats->rx_packets++;

	lb_stats->tx_packets = lb_stats->rx_packets;

	lb_stats = &per_cpu(pcpu_lstats, get_cpu());

	lb_stats->bytes += skb->len;

	lb_stats->packets++;

	put_cpu();



	netif_rx(skb);
@@ -166,20 +168,21 @@ static struct net_device_stats loopback_stats; 
static struct net_device_stats *get_stats(struct net_device *dev)

{

	struct net_device_stats *stats = &loopback_stats;

	unsigned long bytes = 0;

	unsigned long packets = 0;

	int i;



	memset(stats, 0, sizeof(struct net_device_stats));



	for_each_possible_cpu(i) {

		struct net_device_stats *lb_stats;

		const struct pcpu_lstats *lb_stats;



		lb_stats = &per_cpu(loopback_stats, i);

		stats->rx_bytes   += lb_stats->rx_bytes;

		stats->tx_bytes   += lb_stats->tx_bytes;

		stats->rx_packets += lb_stats->rx_packets;

		stats->tx_packets += lb_stats->tx_packets;

		lb_stats = &per_cpu(pcpu_lstats, i);

		bytes   += lb_stats->bytes;

		packets += lb_stats->packets;

	}



	stats->rx_packets = packets;

	stats->tx_packets = packets;

	stats->rx_bytes = bytes;

	stats->tx_bytes = bytes;

	return stats;

}

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