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Merge branch 'tcp-mem-pressure-vs-SO_RCVLOWAT'

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Eric Dumazet says:

====================
tcp: mem pressure vs SO_RCVLOWAT

First patch fixes an issue for applications using SO_RCVLOWAT
to reduce context switches.

Second patch is a cleanup.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2021-02-12 17:28:26 -08:00
commit 762d17b991
3 changed files with 25 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
include/net/tcp.h
View File

@ -1431,12 +1431,29 @@ void tcp_cleanup_rbuf(struct sock *sk, int copied);
*/
static inline bool tcp_rmem_pressure(const struct sock *sk)
{
int rcvbuf = READ_ONCE(sk->sk_rcvbuf);
int threshold = rcvbuf - (rcvbuf >> 3);
int rcvbuf, threshold;
if (tcp_under_memory_pressure(sk))
return true;
rcvbuf = READ_ONCE(sk->sk_rcvbuf);
threshold = rcvbuf - (rcvbuf >> 3);
return atomic_read(&sk->sk_rmem_alloc) > threshold;
}
static inline bool tcp_epollin_ready(const struct sock *sk, int target)
{
const struct tcp_sock *tp = tcp_sk(sk);
int avail = READ_ONCE(tp->rcv_nxt) - READ_ONCE(tp->copied_seq);
if (avail <= 0)
return false;
return (avail >= target) || tcp_rmem_pressure(sk) ||
(tcp_receive_window(tp) <= inet_csk(sk)->icsk_ack.rcv_mss);
}
extern void tcp_openreq_init_rwin(struct request_sock *req,
const struct sock *sk_listener,
const struct dst_entry *dst);

16
net/ipv4/tcp.c
View File

@ -481,19 +481,11 @@ static void tcp_tx_timestamp(struct sock *sk, u16 tsflags)
}
}
static inline bool tcp_stream_is_readable(const struct tcp_sock *tp,
int target, struct sock *sk)
static bool tcp_stream_is_readable(struct sock *sk, int target)
{
int avail = READ_ONCE(tp->rcv_nxt) - READ_ONCE(tp->copied_seq);
if (tcp_epollin_ready(sk, target))
return true;
if (avail > 0) {
if (avail >= target)
return true;
if (tcp_rmem_pressure(sk))
return true;
if (tcp_receive_window(tp) <= inet_csk(sk)->icsk_ack.rcv_mss)
return true;
}
if (sk->sk_prot->stream_memory_read)
return sk->sk_prot->stream_memory_read(sk);
return false;
@ -568,7 +560,7 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
tp->urg_data)
target++;
if (tcp_stream_is_readable(tp, target, sk))
if (tcp_stream_is_readable(sk, target))
mask |= EPOLLIN | EPOLLRDNORM;
if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {

11
net/ipv4/tcp_input.c
View File

@ -4924,15 +4924,8 @@ err:
void tcp_data_ready(struct sock *sk)
{
const struct tcp_sock *tp = tcp_sk(sk);
int avail = tp->rcv_nxt - tp->copied_seq;
if (avail < sk->sk_rcvlowat && !tcp_rmem_pressure(sk) &&
!sock_flag(sk, SOCK_DONE) &&
tcp_receive_window(tp) > inet_csk(sk)->icsk_ack.rcv_mss)
return;
sk->sk_data_ready(sk);
if (tcp_epollin_ready(sk, sk->sk_rcvlowat))
sk->sk_data_ready(sk);
}
static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)