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net: revert "Update RFS target at poll for tcp/udp"

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On multi-threaded processes, one common architecture is to have
one (or a small number of) threads polling sockets, and a
considerably larger pool of threads reading form and writing to the
sockets. When we set RPS core on tcp_poll() or udp_poll() we essentially
steer all packets of all the polled FDs to one (or small number of)
cores, creaing a bottleneck and/or RPS misprediction.

Another common architecture is to shard FDs among threads pinned
to cores. In such a setting, setting RPS core in tcp_poll() and
udp_poll() is redundant because the RFS core is correctly
set in recvmsg and sendmsg.

Thus, revert the following commit:
c3f1dbaf6e ("net: Update RFS target at poll for tcp/udp").

Signed-off-by: Soheil Hassas Yeganeh <[email protected]>
Signed-off-by: Willem de Bruijn <[email protected]>
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: Neal Cardwell <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Soheil Hassas Yeganeh 2018-01-03 21:47:11 -05:00 • committed by David S. Miller
commit 0a38806f31
2 changed files with 0 additions and 4 deletions
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2
net/ipv4/tcp.c
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@ -498,8 +498,6 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
const struct tcp_sock *tp = tcp_sk(sk);
int state;
sock_rps_record_flow(sk);
sock_poll_wait(file, sk_sleep(sk), wait);
state = inet_sk_state_load(sk);

2
net/ipv4/udp.c
View file

@ -2490,8 +2490,6 @@ unsigned int udp_poll(struct file *file, struct socket *sock, poll_table *wait)
if (!skb_queue_empty(&udp_sk(sk)->reader_queue))
mask |= POLLIN | POLLRDNORM;
sock_rps_record_flow(sk);
/* Check for false positives due to checksum errors */
if ((mask & POLLRDNORM) && !(file->f_flags & O_NONBLOCK) &&
!(sk->sk_shutdown & RCV_SHUTDOWN) && first_packet_length(sk) == -1)