diff options
| author | Eric Dumazet <edumazet@google.com> | 2024-10-02 20:30:41 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2024-10-05 01:34:39 +0300 |
| commit | 3b784293016252118ed3b42c5479f20f89a0f384 (patch) | |
| tree | d0070b05b96996fc7944c5ee12fbb8eaa71ed81b /net/ipv4/tcp_timer.c | |
| parent | 5a9071a760a61b00260334ad576fe60debafaafc (diff) | |
| download | linux-3b784293016252118ed3b42c5479f20f89a0f384.tar.xz | |
tcp: add a fast path in tcp_write_timer()
retransmit timer is not stopped from inet_csk_clear_xmit_timer()
because we do not define INET_CSK_CLEAR_TIMERS.
This is a conscious choice : for active TCP flows, it is better
to only call mod_timer(), because there is more chances of
keeping the timer unchanged. Also inet_csk_clear_xmit_timer()
is often called from another cpu, and calling del_timer()
would cause false sharing and lock contention.
This means that very often, tcp_write_timer() is called
at the timer expiration, while there is nothing to retransmit.
This can be detected very early, avoiding the socket spinlock.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241002173042.917928-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/ipv4/tcp_timer.c')
| -rw-r--r-- | net/ipv4/tcp_timer.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index 56c597e763ac..b7266b9101ce 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -717,6 +717,10 @@ static void tcp_write_timer(struct timer_list *t) from_timer(icsk, t, icsk_retransmit_timer); struct sock *sk = &icsk->icsk_inet.sk; + /* Avoid locking the socket when there is no pending event. */ + if (!smp_load_acquire(&icsk->icsk_pending)) + goto out; + bh_lock_sock(sk); if (!sock_owned_by_user(sk)) { tcp_write_timer_handler(sk); @@ -726,6 +730,7 @@ static void tcp_write_timer(struct timer_list *t) sock_hold(sk); } bh_unlock_sock(sk); +out: sock_put(sk); } |