summaryrefslogtreecommitdiffstats
path: root/net/ipv4/tcp_input.c
diff options
context:
space:
mode:
authorEric Dumazet <edumazet@google.com>2020-09-14 12:20:27 +0200
committerDavid S. Miller <davem@davemloft.net>2020-09-14 22:36:00 +0200
commit0cbe6a8f089e5912a577537c97833546d558c357 (patch)
treede1b8b6e854d40adf306ebc7ab79cc73d3cd4133 /net/ipv4/tcp_input.c
parentnet/packet: Fix a comment about hard_header_len and headroom allocation (diff)
downloadlinux-0cbe6a8f089e5912a577537c97833546d558c357.tar.xz
linux-0cbe6a8f089e5912a577537c97833546d558c357.zip
tcp: remove SOCK_QUEUE_SHRUNK
SOCK_QUEUE_SHRUNK is currently used by TCP as a temporary state that remembers if some room has been made in the rtx queue by an incoming ACK packet. This is later used from tcp_check_space() before considering to send EPOLLOUT. Problem is: If we receive SACK packets, and no packet is removed from RTX queue, we can send fresh packets, thus moving them from write queue to rtx queue and eventually empty the write queue. This stall can happen if TCP_NOTSENT_LOWAT is used. With this fix, we no longer risk stalling sends while holes are repaired, and we can fully use socket sndbuf. This also removes a cache line dirtying for typical RPC workloads. Fixes: c9bee3b7fdec ("tcp: TCP_NOTSENT_LOWAT socket option") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Soheil Hassas Yeganeh <soheil@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_input.c')
-rw-r--r--net/ipv4/tcp_input.c23
1 files changed, 7 insertions, 16 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3658ad84f0c6..50834e7f958e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5332,12 +5332,6 @@ static bool tcp_should_expand_sndbuf(const struct sock *sk)
return true;
}
-/* When incoming ACK allowed to free some skb from write_queue,
- * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
- * on the exit from tcp input handler.
- *
- * PROBLEM: sndbuf expansion does not work well with largesend.
- */
static void tcp_new_space(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
@@ -5352,16 +5346,13 @@ static void tcp_new_space(struct sock *sk)
static void tcp_check_space(struct sock *sk)
{
- if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
- sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
- /* pairs with tcp_poll() */
- smp_mb();
- if (sk->sk_socket &&
- test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
- tcp_new_space(sk);
- if (!test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
- tcp_chrono_stop(sk, TCP_CHRONO_SNDBUF_LIMITED);
- }
+ /* pairs with tcp_poll() */
+ smp_mb();
+ if (sk->sk_socket &&
+ test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
+ tcp_new_space(sk);
+ if (!test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
+ tcp_chrono_stop(sk, TCP_CHRONO_SNDBUF_LIMITED);
}
}