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

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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: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2006-10-18 20:51:57 -07:00 • committed by David S. Miller
parent 9ce8ade015
commit 5175c3786c
1 changed files with 19 additions and 16 deletions
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35
drivers/net/loopback.c
View file

@ -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;
}