GitHub-Mirror/Star64_linux
2
0
Fork 0
mirror of https://github.com/Fishwaldo/Star64_linux.git synced 2025-07-23 15:27:29 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

tcp: improve latencies of timer triggered events

Browse source 
Modern TCP stack highly depends on tcp_write_timer() having a small
latency, but current implementation doesn't exactly meet the
expectations.

When a timer fires but finds the socket is owned by the user, it rearms
itself for an additional delay hoping next run will be more
successful.

tcp_write_timer() for example uses a 50ms delay for next try, and it
defeats many attempts to get predictable TCP behavior in term of
latencies.

Use the recently introduced tcp_release_cb(), so that the user owning
the socket will call various handlers right before socket release.

This will permit us to post a followup patch to address the
tcp_tso_should_defer() syndrome (some deferred packets have to wait
RTO timer to be transmitted, while cwnd should allow us to send them
sooner)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Nandita Dukkipati <nanditad@google.com>
Cc: H.K. Jerry Chu <hkchu@google.com>
Cc: John Heffner <johnwheffner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-07-20 05:45:50 +00:00 • committed by David S. Miller
parent 9dc274151a
commit 6f458dfb40
4 changed files with 71 additions and 51 deletions
Download patch file Download diff file Expand all files Collapse all files

70
net/ipv4/tcp_timer.c
View file

@ -32,17 +32,6 @@ int sysctl_tcp_retries2 __read_mostly = TCP_RETR2;
int sysctl_tcp_orphan_retries __read_mostly;
int sysctl_tcp_thin_linear_timeouts __read_mostly;
static void tcp_write_timer(unsigned long);
static void tcp_delack_timer(unsigned long);
static void tcp_keepalive_timer (unsigned long data);
void tcp_init_xmit_timers(struct sock *sk)
{
inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
&tcp_keepalive_timer);
}
EXPORT_SYMBOL(tcp_init_xmit_timers);
static void tcp_write_err(struct sock *sk)
{
sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
@ -205,21 +194,11 @@ static int tcp_write_timeout(struct sock *sk)
return 0;
}
static void tcp_delack_timer(unsigned long data)
void tcp_delack_timer_handler(struct sock *sk)
{
struct sock *sk = (struct sock *)data;
struct tcp_sock *tp = tcp_sk(sk);
struct inet_connection_sock *icsk = inet_csk(sk);
bh_lock_sock(sk);
if (sock_owned_by_user(sk)) {
/* Try again later. */
icsk->icsk_ack.blocked = 1;
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
sk_reset_timer(sk, &icsk->icsk_delack_timer, jiffies + TCP_DELACK_MIN);
goto out_unlock;
}
sk_mem_reclaim_partial(sk);
if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
@ -260,7 +239,21 @@ static void tcp_delack_timer(unsigned long data)
out:
if (sk_under_memory_pressure(sk))
sk_mem_reclaim(sk);
out_unlock:
}
static void tcp_delack_timer(unsigned long data)
{
struct sock *sk = (struct sock *)data;
bh_lock_sock(sk);
if (!sock_owned_by_user(sk)) {
tcp_delack_timer_handler(sk);
} else {
inet_csk(sk)->icsk_ack.blocked = 1;
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
/* deleguate our work to tcp_release_cb() */
set_bit(TCP_WRITE_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags);
}
bh_unlock_sock(sk);
sock_put(sk);
}
@ -450,19 +443,11 @@ out_reset_timer:
out:;
}
static void tcp_write_timer(unsigned long data)
void tcp_write_timer_handler(struct sock *sk)
{
struct sock *sk = (struct sock *)data;
struct inet_connection_sock *icsk = inet_csk(sk);
int event;
bh_lock_sock(sk);
if (sock_owned_by_user(sk)) {
/* Try again later */
sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + (HZ / 20));
goto out_unlock;
}
if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
goto out;
@ -485,7 +470,19 @@ static void tcp_write_timer(unsigned long data)
out:
sk_mem_reclaim(sk);
out_unlock:
}
static void tcp_write_timer(unsigned long data)
{
struct sock *sk = (struct sock *)data;
bh_lock_sock(sk);
if (!sock_owned_by_user(sk)) {
tcp_write_timer_handler(sk);
} else {
/* deleguate our work to tcp_release_cb() */
set_bit(TCP_WRITE_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags);
}
bh_unlock_sock(sk);
sock_put(sk);
}
@ -602,3 +599,10 @@ out:
bh_unlock_sock(sk);
sock_put(sk);
}
void tcp_init_xmit_timers(struct sock *sk)
{
inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
&tcp_keepalive_timer);
}
EXPORT_SYMBOL(tcp_init_xmit_timers);