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sock: avoid dirtying sk_stamp, if possible 

sock_recv_ts_and_drops() unconditionally set sk->sk_stamp for
every packet, even if the SOCK_TIMESTAMP flag is not set in the
related socket.
If selinux is enabled, this cause a cache miss for every packet
since sk->sk_stamp and sk->sk_security share the same cacheline.
With this change sk_stamp is set only if the SOCK_TIMESTAMP
flag is set, and is cleared for the first packet, so that the user
perceived behavior is unchanged.

This gives up to 5% speed-up under udp-flood with small packets.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2017-03-30 14:03:06 +02:00 committed by David S. Miller
parent 7801a3225e
commit 6c7c98bad4
2 changed files with 5 additions and 2 deletions
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5
include/net/sock.h
View File

@ -2239,6 +2239,7 @@ sock_recv_timestamp(struct msghdr *msg, struct sock *sk, struct sk_buff *skb)
void __sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
struct sk_buff *skb);
#define SK_DEFAULT_STAMP (-1L * NSEC_PER_SEC)
static inline void sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
struct sk_buff *skb)
{
@ -2249,8 +2250,10 @@ static inline void sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
if (sk->sk_flags & FLAGS_TS_OR_DROPS || sk->sk_tsflags & TSFLAGS_ANY)
__sock_recv_ts_and_drops(msg, sk, skb);
else
else if (unlikely(sk->sk_flags & SOCK_TIMESTAMP))
sk->sk_stamp = skb->tstamp;
else if (unlikely(sk->sk_stamp == SK_DEFAULT_STAMP))
sk->sk_stamp = 0;
}
void __sock_tx_timestamp(__u16 tsflags, __u8 *tx_flags);

2
net/core/sock.c
View File

@ -2613,7 +2613,7 @@ void sock_init_data(struct socket *sock, struct sock *sk)
sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT;
sk->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
sk->sk_stamp = ktime_set(-1L, 0);
sk->sk_stamp = SK_DEFAULT_STAMP;
#ifdef CONFIG_NET_RX_BUSY_POLL
sk->sk_napi_id = 0;