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authorSoheil Hassas Yeganeh <soheil@google.com>2020-09-14 23:52:09 +0200
committerDavid S. Miller <davem@davemloft.net>2020-09-15 01:58:24 +0200
commit8ba3c9d1c6d75d1e6af2087278b30e17f68e1fff (patch)
treedf6b4e7b5a19abda719a7ad98e369630f70af454
parentionic: fix up debugfs after queue swap (diff)
downloadlinux-8ba3c9d1c6d75d1e6af2087278b30e17f68e1fff.tar.xz
linux-8ba3c9d1c6d75d1e6af2087278b30e17f68e1fff.zip
tcp: return EPOLLOUT from tcp_poll only when notsent_bytes is half the limit
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> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/tcp.c4
1 files 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