Message ID | 20200914215210.2288109-1-soheil.kdev@gmail.com |
---|---|
State | Accepted |
Delegated to: | David Miller |
Headers | show |
Series | [net-next,1/2] tcp: return EPOLLOUT from tcp_poll only when notsent_bytes is half the limit | expand |
From: Soheil Hassas Yeganeh <soheil.kdev@gmail.com> Date: Mon, 14 Sep 2020 17:52:09 -0400 > From: Soheil Hassas Yeganeh <soheil@google.com> > > If there was any event available on the TCP socket, tcp_poll() > will be called to retrieve all the events. In tcp_poll(), we call > sk_stream_is_writeable() which returns true as long as we are at least > one byte below notsent_lowat. This will result in quite a few > spurious EPLLOUT and frequent tiny sendmsg() calls as a result. > > Similar to sk_stream_write_space(), use __sk_stream_is_writeable > with a wake value of 1, so that we set EPOLLOUT only if half the > space is available for write. > > Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> > Signed-off-by: Eric Dumazet <edumazet@google.com> Applied.
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index d3781b6087cb..48c351804efc 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -564,7 +564,7 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait) mask |= EPOLLIN | EPOLLRDNORM; if (!(sk->sk_shutdown & SEND_SHUTDOWN)) { - if (sk_stream_is_writeable(sk)) { + if (__sk_stream_is_writeable(sk, 1)) { mask |= EPOLLOUT | EPOLLWRNORM; } else { /* send SIGIO later */ sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk); @@ -576,7 +576,7 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait) * pairs with the input side. */ smp_mb__after_atomic(); - if (sk_stream_is_writeable(sk)) + if (__sk_stream_is_writeable(sk, 1)) mask |= EPOLLOUT | EPOLLWRNORM; } } else