From: Soheil Hassas Yeganeh <soheil.kdev@gmail•com>
To: davem@davemloft•net, netdev@vger•kernel.org
Cc: edumazet@google•com, Soheil Hassas Yeganeh <soheil@google•com>
Subject: [PATCH net-next 1/2] tcp: return EPOLLOUT from tcp_poll only when notsent_bytes is half the limit
Date: Mon, 14 Sep 2020 17:52:09 -0400 [thread overview]
Message-ID: <20200914215210.2288109-1-soheil.kdev@gmail.com> (raw)
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>
---
net/ipv4/tcp.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
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
--
2.28.0.618.gf4bc123cb7-goog
next reply other threads:[~2020-09-14 21:52 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-14 21:52 Soheil Hassas Yeganeh [this message]
2020-09-14 21:52 ` [PATCH net-next 2/2] tcp: schedule EPOLLOUT after a partial sendmsg Soheil Hassas Yeganeh
2020-09-14 23:58 ` David Miller
2020-09-14 23:58 ` [PATCH net-next 1/2] tcp: return EPOLLOUT from tcp_poll only when notsent_bytes is half the limit David Miller
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