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Subject[RFC PATCH 2/5] tcp: add TCP support for low latency receive poll.
Date
an example of how one could add support for ndo_ll_poll to TCP.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com>
---

net/ipv4/Kconfig | 11 +++++++++++
net/ipv4/tcp.c | 20 ++++++++++++++++++++
net/ipv4/tcp_input.c | 4 ++++
3 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index e52f011..9796aba 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -414,6 +414,17 @@ config INET_LL_RX_POLL

If unsure, say N.

+config INET_LL_TCP_POLL
+ bool "Low Latency TCP Receive Poll"
+ depends on INET_LL_RX_POLL
+ default n
+ ---help---
+ TCP support for Low Latency TCP Queue Poll.
+ (For network cards tht support this option.)
+ Add support to the TCP stack for direct polling of the network card.
+
+ If unsure, say N.
+
config INET_DIAG
tristate "INET: socket monitoring interface"
default y
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 47e854f..e3d1a8e 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -279,6 +279,7 @@

#include <asm/uaccess.h>
#include <asm/ioctls.h>
+#include <net/ll_poll.h>

int sysctl_tcp_fin_timeout __read_mostly = TCP_FIN_TIMEOUT;

@@ -1475,6 +1476,17 @@ int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,

if (sk->sk_state == TCP_LISTEN)
return -ENOTCONN;
+
+#ifdef CONFIG_INET_LL_TCP_POLL
+/* TODO: what do we do if the state changes after sk_poll_ll()? */
+ if (sk_valid_ll(sk) && skb_queue_empty(&sk->sk_receive_queue)
+ && (sk->sk_state == TCP_ESTABLISHED)) {
+
+ release_sock(sk);
+ sk_poll_ll(sk);
+ lock_sock(sk);
+ }
+#endif
while ((skb = tcp_recv_skb(sk, seq, &offset)) != NULL) {
if (offset < skb->len) {
int used;
@@ -1513,6 +1525,7 @@ int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
if (offset + 1 != skb->len)
continue;
}
+ sk_mark_ll(sk, skb);
if (tcp_hdr(skb)->fin) {
sk_eat_skb(sk, skb, false);
++seq;
@@ -1560,6 +1573,12 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
struct sk_buff *skb;
u32 urg_hole = 0;

+#ifdef CONFIG_INET_LL_TCP_POLL
+ if (sk_valid_ll(sk) && skb_queue_empty(&sk->sk_receive_queue)
+ && (sk->sk_state == TCP_ESTABLISHED))
+ sk_poll_ll(sk);
+#endif
+
lock_sock(sk);

err = -ENOTCONN;
@@ -1864,6 +1883,7 @@ do_prequeue:
break;
}
}
+ sk_mark_ll(sk, skb);
}

*seq += used;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a759e19..5c40bd3 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -74,6 +74,7 @@
#include <linux/ipsec.h>
#include <asm/unaligned.h>
#include <net/netdma.h>
+#include <net/ll_poll.h>

int sysctl_tcp_timestamps __read_mostly = 1;
int sysctl_tcp_window_scaling __read_mostly = 1;
@@ -4618,6 +4619,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
tp->copied_seq += chunk;
eaten = (chunk == skb->len);
tcp_rcv_space_adjust(sk);
+ sk_mark_ll(sk, skb);
}
local_bh_disable();
}
@@ -5185,6 +5187,7 @@ static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
tp->ucopy.len -= chunk;
tp->copied_seq += chunk;
tcp_rcv_space_adjust(sk);
+ sk_mark_ll(sk, skb);
}

local_bh_disable();
@@ -5244,6 +5247,7 @@ static bool tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb,
tp->ucopy.len -= chunk;
tp->copied_seq += chunk;
tcp_rcv_space_adjust(sk);
+ sk_mark_ll(sk, skb);

if ((tp->ucopy.len == 0) ||
(tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) ||


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