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net: rfs: add a jump label

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RFS is not commonly used, so add a jump label to avoid some conditionals
in fast path.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-12-07 08:29:10 -08:00 committed by David S. Miller
parent c9fba3ed3a
commit 13bfff25c0
4 changed files with 21 additions and 12 deletions
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1
include/linux/netdevice.h
View file

@ -192,6 +192,7 @@ struct net_device_stats {
#ifdef CONFIG_RPS
#include <linux/static_key.h>
extern struct static_key rps_needed;
extern struct static_key rfs_needed;
#endif
struct neighbour;

25
include/net/sock.h
View file

@ -913,17 +913,20 @@ static inline void sock_rps_record_flow_hash(__u32 hash)
static inline void sock_rps_record_flow(const struct sock *sk)
{
#ifdef CONFIG_RPS
/* Reading sk->sk_rxhash might incur an expensive cache line miss.
*
* TCP_ESTABLISHED does cover almost all states where RFS
* might be useful, and is cheaper [1] than testing :
* IPv4: inet_sk(sk)->inet_daddr
* IPv6: ipv6_addr_any(&sk->sk_v6_daddr)
* OR an additional socket flag
* [1] : sk_state and sk_prot are in the same cache line.
*/
if (sk->sk_state == TCP_ESTABLISHED)
sock_rps_record_flow_hash(sk->sk_rxhash);
if (static_key_false(&rfs_needed)) {
/* Reading sk->sk_rxhash might incur an expensive cache line
* miss.
*
* TCP_ESTABLISHED does cover almost all states where RFS
* might be useful, and is cheaper [1] than testing :
* IPv4: inet_sk(sk)->inet_daddr
* IPv6: ipv6_addr_any(&sk->sk_v6_daddr)
* OR an additional socket flag
* [1] : sk_state and sk_prot are in the same cache line.
*/
if (sk->sk_state == TCP_ESTABLISHED)
sock_rps_record_flow_hash(sk->sk_rxhash);
}
#endif
}

2
net/core/dev.c
View file

@ -3447,6 +3447,8 @@ EXPORT_SYMBOL(rps_cpu_mask);
struct static_key rps_needed __read_mostly;
EXPORT_SYMBOL(rps_needed);
struct static_key rfs_needed __read_mostly;
EXPORT_SYMBOL(rfs_needed);
static struct rps_dev_flow *
set_rps_cpu(struct net_device *dev, struct sk_buff *skb,

5
net/core/sysctl_net_core.c
View file

@ -79,10 +79,13 @@ static int rps_sock_flow_sysctl(struct ctl_table *table, int write,
if (sock_table != orig_sock_table) {
rcu_assign_pointer(rps_sock_flow_table, sock_table);
if (sock_table)
if (sock_table) {
static_key_slow_inc(&rps_needed);
static_key_slow_inc(&rfs_needed);
}
if (orig_sock_table) {
static_key_slow_dec(&rps_needed);
static_key_slow_dec(&rfs_needed);
synchronize_rcu();
vfree(orig_sock_table);
}