diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index f485d553e65c..84c9b8cee780 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -353,12 +353,7 @@ tcp_l3mdev_accept - BOOLEAN
 	compiled with CONFIG_NET_L3_MASTER_DEV.
 
 tcp_low_latency - BOOLEAN
-	If set, the TCP stack makes decisions that prefer lower
-	latency as opposed to higher throughput.  By default, this
-	option is not set meaning that higher throughput is preferred.
-	An example of an application where this default should be
-	changed would be a Beowulf compute cluster.
-	Default: 0
+	This is a legacy option, it has no effect anymore.
 
 tcp_max_orphans - INTEGER
 	Maximal number of TCP sockets not attached to any user file handle,
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 542ca1ae02c4..d7389ea36e10 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -147,12 +147,6 @@ struct tcp_sock {
 	u16	tcp_header_len;	/* Bytes of tcp header to send		*/
 	u16	gso_segs;	/* Max number of segs per GSO packet	*/
 
-/*
- *	Header prediction flags
- *	0x5?10 << 16 + snd_wnd in net byte order
- */
-	__be32	pred_flags;
-
 /*
  *	RFC793 variables by their proper names. This means you can
  *	read the code and the spec side by side (and laugh ...)
@@ -192,15 +186,6 @@ struct tcp_sock {
 
 	struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
 
-	/* Data for direct copy to user */
-	struct {
-		struct sk_buff_head	prequeue;
-		struct task_struct	*task;
-		struct msghdr		*msg;
-		int			memory;
-		int			len;
-	} ucopy;
-
 	u32	snd_wl1;	/* Sequence for window update		*/
 	u32	snd_wnd;	/* The window we expect to receive	*/
 	u32	max_window;	/* Maximal window ever seen from peer	*/
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 12d68335acd4..3ecb62811004 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -256,7 +256,6 @@ extern int sysctl_tcp_rmem[3];
 extern int sysctl_tcp_app_win;
 extern int sysctl_tcp_adv_win_scale;
 extern int sysctl_tcp_frto;
-extern int sysctl_tcp_low_latency;
 extern int sysctl_tcp_nometrics_save;
 extern int sysctl_tcp_moderate_rcvbuf;
 extern int sysctl_tcp_tso_win_divisor;
@@ -632,29 +631,6 @@ static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
 	return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
 }
 
-static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
-{
-	tp->pred_flags = htonl((tp->tcp_header_len << 26) |
-			       ntohl(TCP_FLAG_ACK) |
-			       snd_wnd);
-}
-
-static inline void tcp_fast_path_on(struct tcp_sock *tp)
-{
-	__tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
-}
-
-static inline void tcp_fast_path_check(struct sock *sk)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-
-	if (RB_EMPTY_ROOT(&tp->out_of_order_queue) &&
-	    tp->rcv_wnd &&
-	    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
-	    !tp->urg_data)
-		tcp_fast_path_on(tp);
-}
-
 /* Compute the actual rto_min value */
 static inline u32 tcp_rto_min(struct sock *sk)
 {
@@ -904,9 +880,8 @@ enum tcp_ca_event {
 
 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
 enum tcp_ca_ack_event_flags {
-	CA_ACK_SLOWPATH		= (1 << 0),	/* In slow path processing */
-	CA_ACK_WIN_UPDATE	= (1 << 1),	/* ACK updated window */
-	CA_ACK_ECE		= (1 << 2),	/* ECE bit is set on ack */
+	CA_ACK_WIN_UPDATE	= (1 << 0),	/* ACK updated window */
+	CA_ACK_ECE		= (1 << 1),	/* ECE bit is set on ack */
 };
 
 /*
@@ -1244,17 +1219,6 @@ static inline bool tcp_checksum_complete(struct sk_buff *skb)
 		__tcp_checksum_complete(skb);
 }
 
-/* Prequeue for VJ style copy to user, combined with checksumming. */
-
-static inline void tcp_prequeue_init(struct tcp_sock *tp)
-{
-	tp->ucopy.task = NULL;
-	tp->ucopy.len = 0;
-	tp->ucopy.memory = 0;
-	skb_queue_head_init(&tp->ucopy.prequeue);
-}
-
-bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
 bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb);
 int tcp_filter(struct sock *sk, struct sk_buff *skb);
 
diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index d85693295798..b3f346fb9fe3 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -184,14 +184,7 @@ enum
 	LINUX_MIB_DELAYEDACKLOST,		/* DelayedACKLost */
 	LINUX_MIB_LISTENOVERFLOWS,		/* ListenOverflows */
 	LINUX_MIB_LISTENDROPS,			/* ListenDrops */
-	LINUX_MIB_TCPPREQUEUED,			/* TCPPrequeued */
-	LINUX_MIB_TCPDIRECTCOPYFROMBACKLOG,	/* TCPDirectCopyFromBacklog */
-	LINUX_MIB_TCPDIRECTCOPYFROMPREQUEUE,	/* TCPDirectCopyFromPrequeue */
-	LINUX_MIB_TCPPREQUEUEDROPPED,		/* TCPPrequeueDropped */
-	LINUX_MIB_TCPHPHITS,			/* TCPHPHits */
-	LINUX_MIB_TCPHPHITSTOUSER,		/* TCPHPHitsToUser */
 	LINUX_MIB_TCPPUREACKS,			/* TCPPureAcks */
-	LINUX_MIB_TCPHPACKS,			/* TCPHPAcks */
 	LINUX_MIB_TCPRENORECOVERY,		/* TCPRenoRecovery */
 	LINUX_MIB_TCPSACKRECOVERY,		/* TCPSackRecovery */
 	LINUX_MIB_TCPSACKRENEGING,		/* TCPSACKReneging */
@@ -208,14 +201,12 @@ enum
 	LINUX_MIB_TCPSACKFAILURES,		/* TCPSackFailures */
 	LINUX_MIB_TCPLOSSFAILURES,		/* TCPLossFailures */
 	LINUX_MIB_TCPFASTRETRANS,		/* TCPFastRetrans */
-	LINUX_MIB_TCPFORWARDRETRANS,		/* TCPForwardRetrans */
 	LINUX_MIB_TCPSLOWSTARTRETRANS,		/* TCPSlowStartRetrans */
 	LINUX_MIB_TCPTIMEOUTS,			/* TCPTimeouts */
 	LINUX_MIB_TCPLOSSPROBES,		/* TCPLossProbes */
 	LINUX_MIB_TCPLOSSPROBERECOVERY,		/* TCPLossProbeRecovery */
 	LINUX_MIB_TCPRENORECOVERYFAIL,		/* TCPRenoRecoveryFail */
 	LINUX_MIB_TCPSACKRECOVERYFAIL,		/* TCPSackRecoveryFail */
-	LINUX_MIB_TCPSCHEDULERFAILED,		/* TCPSchedulerFailed */
 	LINUX_MIB_TCPRCVCOLLAPSED,		/* TCPRcvCollapsed */
 	LINUX_MIB_TCPDSACKOLDSENT,		/* TCPDSACKOldSent */
 	LINUX_MIB_TCPDSACKOFOSENT,		/* TCPDSACKOfoSent */
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 43eb6567b3a0..b6d3fe03feb3 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -206,14 +206,7 @@ static const struct snmp_mib snmp4_net_list[] = {
 	SNMP_MIB_ITEM("DelayedACKLost", LINUX_MIB_DELAYEDACKLOST),
 	SNMP_MIB_ITEM("ListenOverflows", LINUX_MIB_LISTENOVERFLOWS),
 	SNMP_MIB_ITEM("ListenDrops", LINUX_MIB_LISTENDROPS),
-	SNMP_MIB_ITEM("TCPPrequeued", LINUX_MIB_TCPPREQUEUED),
-	SNMP_MIB_ITEM("TCPDirectCopyFromBacklog", LINUX_MIB_TCPDIRECTCOPYFROMBACKLOG),
-	SNMP_MIB_ITEM("TCPDirectCopyFromPrequeue", LINUX_MIB_TCPDIRECTCOPYFROMPREQUEUE),
-	SNMP_MIB_ITEM("TCPPrequeueDropped", LINUX_MIB_TCPPREQUEUEDROPPED),
-	SNMP_MIB_ITEM("TCPHPHits", LINUX_MIB_TCPHPHITS),
-	SNMP_MIB_ITEM("TCPHPHitsToUser", LINUX_MIB_TCPHPHITSTOUSER),
 	SNMP_MIB_ITEM("TCPPureAcks", LINUX_MIB_TCPPUREACKS),
-	SNMP_MIB_ITEM("TCPHPAcks", LINUX_MIB_TCPHPACKS),
 	SNMP_MIB_ITEM("TCPRenoRecovery", LINUX_MIB_TCPRENORECOVERY),
 	SNMP_MIB_ITEM("TCPSackRecovery", LINUX_MIB_TCPSACKRECOVERY),
 	SNMP_MIB_ITEM("TCPSACKReneging", LINUX_MIB_TCPSACKRENEGING),
@@ -230,14 +223,12 @@ static const struct snmp_mib snmp4_net_list[] = {
 	SNMP_MIB_ITEM("TCPSackFailures", LINUX_MIB_TCPSACKFAILURES),
 	SNMP_MIB_ITEM("TCPLossFailures", LINUX_MIB_TCPLOSSFAILURES),
 	SNMP_MIB_ITEM("TCPFastRetrans", LINUX_MIB_TCPFASTRETRANS),
-	SNMP_MIB_ITEM("TCPForwardRetrans", LINUX_MIB_TCPFORWARDRETRANS),
 	SNMP_MIB_ITEM("TCPSlowStartRetrans", LINUX_MIB_TCPSLOWSTARTRETRANS),
 	SNMP_MIB_ITEM("TCPTimeouts", LINUX_MIB_TCPTIMEOUTS),
 	SNMP_MIB_ITEM("TCPLossProbes", LINUX_MIB_TCPLOSSPROBES),
 	SNMP_MIB_ITEM("TCPLossProbeRecovery", LINUX_MIB_TCPLOSSPROBERECOVERY),
 	SNMP_MIB_ITEM("TCPRenoRecoveryFail", LINUX_MIB_TCPRENORECOVERYFAIL),
 	SNMP_MIB_ITEM("TCPSackRecoveryFail", LINUX_MIB_TCPSACKRECOVERYFAIL),
-	SNMP_MIB_ITEM("TCPSchedulerFailed", LINUX_MIB_TCPSCHEDULERFAILED),
 	SNMP_MIB_ITEM("TCPRcvCollapsed", LINUX_MIB_TCPRCVCOLLAPSED),
 	SNMP_MIB_ITEM("TCPDSACKOldSent", LINUX_MIB_TCPDSACKOLDSENT),
 	SNMP_MIB_ITEM("TCPDSACKOfoSent", LINUX_MIB_TCPDSACKOFOSENT),
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 9bf809726066..0d3c038d7b04 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -45,6 +45,9 @@ static int tcp_syn_retries_max = MAX_TCP_SYNCNT;
 static int ip_ping_group_range_min[] = { 0, 0 };
 static int ip_ping_group_range_max[] = { GID_T_MAX, GID_T_MAX };
 
+/* obsolete */
+static int sysctl_tcp_low_latency __read_mostly;
+
 /* Update system visible IP port range */
 static void set_local_port_range(struct net *net, int range[2])
 {
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 71ce33decd97..e022874d509f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -400,7 +400,6 @@ void tcp_init_sock(struct sock *sk)
 
 	tp->out_of_order_queue = RB_ROOT;
 	tcp_init_xmit_timers(sk);
-	tcp_prequeue_init(tp);
 	INIT_LIST_HEAD(&tp->tsq_node);
 
 	icsk->icsk_rto = TCP_TIMEOUT_INIT;
@@ -1525,20 +1524,6 @@ static void tcp_cleanup_rbuf(struct sock *sk, int copied)
 		tcp_send_ack(sk);
 }
 
-static void tcp_prequeue_process(struct sock *sk)
-{
-	struct sk_buff *skb;
-	struct tcp_sock *tp = tcp_sk(sk);
-
-	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPREQUEUED);
-
-	while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
-		sk_backlog_rcv(sk, skb);
-
-	/* Clear memory counter. */
-	tp->ucopy.memory = 0;
-}
-
 static struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off)
 {
 	struct sk_buff *skb;
@@ -1671,7 +1656,6 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
 	int err;
 	int target;		/* Read at least this many bytes */
 	long timeo;
-	struct task_struct *user_recv = NULL;
 	struct sk_buff *skb, *last;
 	u32 urg_hole = 0;
 
@@ -1806,51 +1790,6 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
 
 		tcp_cleanup_rbuf(sk, copied);
 
-		if (!sysctl_tcp_low_latency && tp->ucopy.task == user_recv) {
-			/* Install new reader */
-			if (!user_recv && !(flags & (MSG_TRUNC | MSG_PEEK))) {
-				user_recv = current;
-				tp->ucopy.task = user_recv;
-				tp->ucopy.msg = msg;
-			}
-
-			tp->ucopy.len = len;
-
-			WARN_ON(tp->copied_seq != tp->rcv_nxt &&
-				!(flags & (MSG_PEEK | MSG_TRUNC)));
-
-			/* Ugly... If prequeue is not empty, we have to
-			 * process it before releasing socket, otherwise
-			 * order will be broken at second iteration.
-			 * More elegant solution is required!!!
-			 *
-			 * Look: we have the following (pseudo)queues:
-			 *
-			 * 1. packets in flight
-			 * 2. backlog
-			 * 3. prequeue
-			 * 4. receive_queue
-			 *
-			 * Each queue can be processed only if the next ones
-			 * are empty. At this point we have empty receive_queue.
-			 * But prequeue _can_ be not empty after 2nd iteration,
-			 * when we jumped to start of loop because backlog
-			 * processing added something to receive_queue.
-			 * We cannot release_sock(), because backlog contains
-			 * packets arrived _after_ prequeued ones.
-			 *
-			 * Shortly, algorithm is clear --- to process all
-			 * the queues in order. We could make it more directly,
-			 * requeueing packets from backlog to prequeue, if
-			 * is not empty. It is more elegant, but eats cycles,
-			 * unfortunately.
-			 */
-			if (!skb_queue_empty(&tp->ucopy.prequeue))
-				goto do_prequeue;
-
-			/* __ Set realtime policy in scheduler __ */
-		}
-
 		if (copied >= target) {
 			/* Do not sleep, just process backlog. */
 			release_sock(sk);
@@ -1859,31 +1798,6 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
 			sk_wait_data(sk, &timeo, last);
 		}
 
-		if (user_recv) {
-			int chunk;
-
-			/* __ Restore normal policy in scheduler __ */
-
-			chunk = len - tp->ucopy.len;
-			if (chunk != 0) {
-				NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPDIRECTCOPYFROMBACKLOG, chunk);
-				len -= chunk;
-				copied += chunk;
-			}
-
-			if (tp->rcv_nxt == tp->copied_seq &&
-			    !skb_queue_empty(&tp->ucopy.prequeue)) {
-do_prequeue:
-				tcp_prequeue_process(sk);
-
-				chunk = len - tp->ucopy.len;
-				if (chunk != 0) {
-					NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPDIRECTCOPYFROMPREQUEUE, chunk);
-					len -= chunk;
-					copied += chunk;
-				}
-			}
-		}
 		if ((flags & MSG_PEEK) &&
 		    (peek_seq - copied - urg_hole != tp->copied_seq)) {
 			net_dbg_ratelimited("TCP(%s:%d): Application bug, race in MSG_PEEK\n",
@@ -1934,10 +1848,8 @@ do_prequeue:
 		tcp_rcv_space_adjust(sk);
 
 skip_copy:
-		if (tp->urg_data && after(tp->copied_seq, tp->urg_seq)) {
+		if (tp->urg_data && after(tp->copied_seq, tp->urg_seq))
 			tp->urg_data = 0;
-			tcp_fast_path_check(sk);
-		}
 		if (used + offset < skb->len)
 			continue;
 
@@ -1955,25 +1867,6 @@ skip_copy:
 		break;
 	} while (len > 0);
 
-	if (user_recv) {
-		if (!skb_queue_empty(&tp->ucopy.prequeue)) {
-			int chunk;
-
-			tp->ucopy.len = copied > 0 ? len : 0;
-
-			tcp_prequeue_process(sk);
-
-			if (copied > 0 && (chunk = len - tp->ucopy.len) != 0) {
-				NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPDIRECTCOPYFROMPREQUEUE, chunk);
-				len -= chunk;
-				copied += chunk;
-			}
-		}
-
-		tp->ucopy.task = NULL;
-		tp->ucopy.len = 0;
-	}
-
 	/* According to UNIX98, msg_name/msg_namelen are ignored
 	 * on connected socket. I was just happy when found this 8) --ANK
 	 */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index adc3f3e9468c..af0a98d54b62 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -103,7 +103,6 @@ int sysctl_tcp_invalid_ratelimit __read_mostly = HZ/2;
 #define FLAG_DATA_SACKED	0x20 /* New SACK.				*/
 #define FLAG_ECE		0x40 /* ECE in this ACK				*/
 #define FLAG_LOST_RETRANS	0x80 /* This ACK marks some retransmission lost */
-#define FLAG_SLOWPATH		0x100 /* Do not skip RFC checks for window update.*/
 #define FLAG_ORIG_SACK_ACKED	0x200 /* Never retransmitted data are (s)acked	*/
 #define FLAG_SND_UNA_ADVANCED	0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
 #define FLAG_DSACKING_ACK	0x800 /* SACK blocks contained D-SACK info */
@@ -3367,12 +3366,6 @@ static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32
 		if (tp->snd_wnd != nwin) {
 			tp->snd_wnd = nwin;
 
-			/* Note, it is the only place, where
-			 * fast path is recovered for sending TCP.
-			 */
-			tp->pred_flags = 0;
-			tcp_fast_path_check(sk);
-
 			if (tcp_send_head(sk))
 				tcp_slow_start_after_idle_check(sk);
 
@@ -3554,6 +3547,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	u32 lost = tp->lost;
 	int acked = 0; /* Number of packets newly acked */
 	int rexmit = REXMIT_NONE; /* Flag to (re)transmit to recover losses */
+	u32 ack_ev_flags = 0;
 
 	sack_state.first_sackt = 0;
 	sack_state.rate = &rs;
@@ -3597,43 +3591,27 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	if (flag & FLAG_UPDATE_TS_RECENT)
 		tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
 
-	if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
-		/* Window is constant, pure forward advance.
-		 * No more checks are required.
-		 * Note, we use the fact that SND.UNA>=SND.WL2.
-		 */
-		tcp_update_wl(tp, ack_seq);
-		tcp_snd_una_update(tp, ack);
-		flag |= FLAG_WIN_UPDATE;
+	if (ack_seq != TCP_SKB_CB(skb)->end_seq)
+		flag |= FLAG_DATA;
+	else
+		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPUREACKS);
 
-		tcp_in_ack_event(sk, CA_ACK_WIN_UPDATE);
+	flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
 
-		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPACKS);
-	} else {
-		u32 ack_ev_flags = CA_ACK_SLOWPATH;
+	if (TCP_SKB_CB(skb)->sacked)
+		flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
+						&sack_state);
 
-		if (ack_seq != TCP_SKB_CB(skb)->end_seq)
-			flag |= FLAG_DATA;
-		else
-			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPUREACKS);
-
-		flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
-
-		if (TCP_SKB_CB(skb)->sacked)
-			flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
-							&sack_state);
-
-		if (tcp_ecn_rcv_ecn_echo(tp, tcp_hdr(skb))) {
-			flag |= FLAG_ECE;
-			ack_ev_flags |= CA_ACK_ECE;
-		}
-
-		if (flag & FLAG_WIN_UPDATE)
-			ack_ev_flags |= CA_ACK_WIN_UPDATE;
-
-		tcp_in_ack_event(sk, ack_ev_flags);
+	if (tcp_ecn_rcv_ecn_echo(tp, tcp_hdr(skb))) {
+		flag |= FLAG_ECE;
+		ack_ev_flags = CA_ACK_ECE;
 	}
 
+	if (flag & FLAG_WIN_UPDATE)
+		ack_ev_flags |= CA_ACK_WIN_UPDATE;
+
+	tcp_in_ack_event(sk, ack_ev_flags);
+
 	/* We passed data and got it acked, remove any soft error
 	 * log. Something worked...
 	 */
@@ -4398,8 +4376,6 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 		return;
 	}
 
-	/* Disable header prediction. */
-	tp->pred_flags = 0;
 	inet_csk_schedule_ack(sk);
 
 	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOQUEUE);
@@ -4611,32 +4587,14 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 			goto out_of_window;
 
 		/* Ok. In sequence. In window. */
-		if (tp->ucopy.task == current &&
-		    tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
-		    sock_owned_by_user(sk) && !tp->urg_data) {
-			int chunk = min_t(unsigned int, skb->len,
-					  tp->ucopy.len);
-
-			__set_current_state(TASK_RUNNING);
-
-			if (!skb_copy_datagram_msg(skb, 0, tp->ucopy.msg, chunk)) {
-				tp->ucopy.len -= chunk;
-				tp->copied_seq += chunk;
-				eaten = (chunk == skb->len);
-				tcp_rcv_space_adjust(sk);
-			}
-		}
-
-		if (eaten <= 0) {
 queue_and_out:
-			if (eaten < 0) {
-				if (skb_queue_len(&sk->sk_receive_queue) == 0)
-					sk_forced_mem_schedule(sk, skb->truesize);
-				else if (tcp_try_rmem_schedule(sk, skb, skb->truesize))
-					goto drop;
-			}
-			eaten = tcp_queue_rcv(sk, skb, 0, &fragstolen);
+		if (eaten < 0) {
+			if (skb_queue_len(&sk->sk_receive_queue) == 0)
+				sk_forced_mem_schedule(sk, skb->truesize);
+			else if (tcp_try_rmem_schedule(sk, skb, skb->truesize))
+				goto drop;
 		}
+		eaten = tcp_queue_rcv(sk, skb, 0, &fragstolen);
 		tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
 		if (skb->len)
 			tcp_event_data_recv(sk, skb);
@@ -4656,8 +4614,6 @@ queue_and_out:
 		if (tp->rx_opt.num_sacks)
 			tcp_sack_remove(tp);
 
-		tcp_fast_path_check(sk);
-
 		if (eaten > 0)
 			kfree_skb_partial(skb, fragstolen);
 		if (!sock_flag(sk, SOCK_DEAD))
@@ -4983,7 +4939,6 @@ static int tcp_prune_queue(struct sock *sk)
 	NET_INC_STATS(sock_net(sk), LINUX_MIB_RCVPRUNED);
 
 	/* Massive buffer overcommit. */
-	tp->pred_flags = 0;
 	return -1;
 }
 
@@ -5155,9 +5110,6 @@ static void tcp_check_urg(struct sock *sk, const struct tcphdr *th)
 
 	tp->urg_data = TCP_URG_NOTYET;
 	tp->urg_seq = ptr;
-
-	/* Disable header prediction. */
-	tp->pred_flags = 0;
 }
 
 /* This is the 'fast' part of urgent handling. */
@@ -5186,26 +5138,6 @@ static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *t
 	}
 }
 
-static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-	int chunk = skb->len - hlen;
-	int err;
-
-	if (skb_csum_unnecessary(skb))
-		err = skb_copy_datagram_msg(skb, hlen, tp->ucopy.msg, chunk);
-	else
-		err = skb_copy_and_csum_datagram_msg(skb, hlen, tp->ucopy.msg);
-
-	if (!err) {
-		tp->ucopy.len -= chunk;
-		tp->copied_seq += chunk;
-		tcp_rcv_space_adjust(sk);
-	}
-
-	return err;
-}
-
 /* Accept RST for rcv_nxt - 1 after a FIN.
  * When tcp connections are abruptly terminated from Mac OSX (via ^C), a
  * FIN is sent followed by a RST packet. The RST is sent with the same
@@ -5336,26 +5268,6 @@ discard:
 
 /*
  *	TCP receive function for the ESTABLISHED state.
- *
- *	It is split into a fast path and a slow path. The fast path is
- * 	disabled when:
- *	- A zero window was announced from us - zero window probing
- *        is only handled properly in the slow path.
- *	- Out of order segments arrived.
- *	- Urgent data is expected.
- *	- There is no buffer space left
- *	- Unexpected TCP flags/window values/header lengths are received
- *	  (detected by checking the TCP header against pred_flags)
- *	- Data is sent in both directions. Fast path only supports pure senders
- *	  or pure receivers (this means either the sequence number or the ack
- *	  value must stay constant)
- *	- Unexpected TCP option.
- *
- *	When these conditions are not satisfied it drops into a standard
- *	receive procedure patterned after RFC793 to handle all cases.
- *	The first three cases are guaranteed by proper pred_flags setting,
- *	the rest is checked inline. Fast processing is turned on in
- *	tcp_data_queue when everything is OK.
  */
 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 			 const struct tcphdr *th)
@@ -5366,172 +5278,19 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 	tcp_mstamp_refresh(tp);
 	if (unlikely(!sk->sk_rx_dst))
 		inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb);
-	/*
-	 *	Header prediction.
-	 *	The code loosely follows the one in the famous
-	 *	"30 instruction TCP receive" Van Jacobson mail.
-	 *
-	 *	Van's trick is to deposit buffers into socket queue
-	 *	on a device interrupt, to call tcp_recv function
-	 *	on the receive process context and checksum and copy
-	 *	the buffer to user space. smart...
-	 *
-	 *	Our current scheme is not silly either but we take the
-	 *	extra cost of the net_bh soft interrupt processing...
-	 *	We do checksum and copy also but from device to kernel.
-	 */
 
 	tp->rx_opt.saw_tstamp = 0;
 
-	/*	pred_flags is 0xS?10 << 16 + snd_wnd
-	 *	if header_prediction is to be made
-	 *	'S' will always be tp->tcp_header_len >> 2
-	 *	'?' will be 0 for the fast path, otherwise pred_flags is 0 to
-	 *  turn it off	(when there are holes in the receive
-	 *	 space for instance)
-	 *	PSH flag is ignored.
-	 */
-
-	if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
-	    TCP_SKB_CB(skb)->seq == tp->rcv_nxt &&
-	    !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
-		int tcp_header_len = tp->tcp_header_len;
-
-		/* Timestamp header prediction: tcp_header_len
-		 * is automatically equal to th->doff*4 due to pred_flags
-		 * match.
-		 */
-
-		/* Check timestamp */
-		if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
-			/* No? Slow path! */
-			if (!tcp_parse_aligned_timestamp(tp, th))
-				goto slow_path;
-
-			/* If PAWS failed, check it more carefully in slow path */
-			if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
-				goto slow_path;
-
-			/* DO NOT update ts_recent here, if checksum fails
-			 * and timestamp was corrupted part, it will result
-			 * in a hung connection since we will drop all
-			 * future packets due to the PAWS test.
-			 */
-		}
-
-		if (len <= tcp_header_len) {
-			/* Bulk data transfer: sender */
-			if (len == tcp_header_len) {
-				/* Predicted packet is in window by definition.
-				 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
-				 * Hence, check seq<=rcv_wup reduces to:
-				 */
-				if (tcp_header_len ==
-				    (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
-				    tp->rcv_nxt == tp->rcv_wup)
-					tcp_store_ts_recent(tp);
-
-				/* We know that such packets are checksummed
-				 * on entry.
-				 */
-				tcp_ack(sk, skb, 0);
-				__kfree_skb(skb);
-				tcp_data_snd_check(sk);
-				return;
-			} else { /* Header too small */
-				TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
-				goto discard;
-			}
-		} else {
-			int eaten = 0;
-			bool fragstolen = false;
-
-			if (tp->ucopy.task == current &&
-			    tp->copied_seq == tp->rcv_nxt &&
-			    len - tcp_header_len <= tp->ucopy.len &&
-			    sock_owned_by_user(sk)) {
-				__set_current_state(TASK_RUNNING);
-
-				if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) {
-					/* Predicted packet is in window by definition.
-					 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
-					 * Hence, check seq<=rcv_wup reduces to:
-					 */
-					if (tcp_header_len ==
-					    (sizeof(struct tcphdr) +
-					     TCPOLEN_TSTAMP_ALIGNED) &&
-					    tp->rcv_nxt == tp->rcv_wup)
-						tcp_store_ts_recent(tp);
-
-					tcp_rcv_rtt_measure_ts(sk, skb);
-
-					__skb_pull(skb, tcp_header_len);
-					tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
-					NET_INC_STATS(sock_net(sk),
-							LINUX_MIB_TCPHPHITSTOUSER);
-					eaten = 1;
-				}
-			}
-			if (!eaten) {
-				if (tcp_checksum_complete(skb))
-					goto csum_error;
-
-				if ((int)skb->truesize > sk->sk_forward_alloc)
-					goto step5;
-
-				/* Predicted packet is in window by definition.
-				 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
-				 * Hence, check seq<=rcv_wup reduces to:
-				 */
-				if (tcp_header_len ==
-				    (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
-				    tp->rcv_nxt == tp->rcv_wup)
-					tcp_store_ts_recent(tp);
-
-				tcp_rcv_rtt_measure_ts(sk, skb);
-
-				NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPHITS);
-
-				/* Bulk data transfer: receiver */
-				eaten = tcp_queue_rcv(sk, skb, tcp_header_len,
-						      &fragstolen);
-			}
-
-			tcp_event_data_recv(sk, skb);
-
-			if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
-				/* Well, only one small jumplet in fast path... */
-				tcp_ack(sk, skb, FLAG_DATA);
-				tcp_data_snd_check(sk);
-				if (!inet_csk_ack_scheduled(sk))
-					goto no_ack;
-			}
-
-			__tcp_ack_snd_check(sk, 0);
-no_ack:
-			if (eaten)
-				kfree_skb_partial(skb, fragstolen);
-			sk->sk_data_ready(sk);
-			return;
-		}
-	}
-
-slow_path:
 	if (len < (th->doff << 2) || tcp_checksum_complete(skb))
 		goto csum_error;
 
 	if (!th->ack && !th->rst && !th->syn)
 		goto discard;
 
-	/*
-	 *	Standard slow path.
-	 */
-
 	if (!tcp_validate_incoming(sk, skb, th, 1))
 		return;
 
-step5:
-	if (tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT) < 0)
+	if (tcp_ack(sk, skb, FLAG_UPDATE_TS_RECENT) < 0)
 		goto discard;
 
 	tcp_rcv_rtt_measure_ts(sk, skb);
@@ -5585,11 +5344,10 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
 	if (sock_flag(sk, SOCK_KEEPOPEN))
 		inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
 
-	if (!tp->rx_opt.snd_wscale)
-		__tcp_fast_path_on(tp, tp->snd_wnd);
-	else
-		tp->pred_flags = 0;
-
+	if (!sock_flag(sk, SOCK_DEAD)) {
+		sk->sk_state_change(sk);
+		sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
+	}
 }
 
 static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
@@ -5718,7 +5476,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
 		tcp_ecn_rcv_synack(tp, th);
 
 		tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
-		tcp_ack(sk, skb, FLAG_SLOWPATH);
+		tcp_ack(sk, skb, 0);
 
 		/* Ok.. it's good. Set up sequence numbers and
 		 * move to established.
@@ -5954,8 +5712,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 		return 0;
 
 	/* step 5: check the ACK field */
-	acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH |
-				      FLAG_UPDATE_TS_RECENT |
+
+	acceptable = tcp_ack(sk, skb, FLAG_UPDATE_TS_RECENT |
 				      FLAG_NO_CHALLENGE_ACK) > 0;
 
 	if (!acceptable) {
@@ -6023,7 +5781,6 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 		tp->lsndtime = tcp_jiffies32;
 
 		tcp_initialize_rcv_mss(sk);
-		tcp_fast_path_on(tp);
 		break;
 
 	case TCP_FIN_WAIT1: {
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 3a19ea28339f..9b51663cd5a4 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -85,8 +85,6 @@
 #include <crypto/hash.h>
 #include <linux/scatterlist.h>
 
-int sysctl_tcp_low_latency __read_mostly;
-
 #ifdef CONFIG_TCP_MD5SIG
 static int tcp_v4_md5_hash_hdr(char *md5_hash, const struct tcp_md5sig_key *key,
 			       __be32 daddr, __be32 saddr, const struct tcphdr *th);
@@ -1541,61 +1539,6 @@ void tcp_v4_early_demux(struct sk_buff *skb)
 	}
 }
 
-/* Packet is added to VJ-style prequeue for processing in process
- * context, if a reader task is waiting. Apparently, this exciting
- * idea (VJ's mail "Re: query about TCP header on tcp-ip" of 07 Sep 93)
- * failed somewhere. Latency? Burstiness? Well, at least now we will
- * see, why it failed. 8)8)				  --ANK
- *
- */
-bool tcp_prequeue(struct sock *sk, struct sk_buff *skb)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-
-	if (sysctl_tcp_low_latency || !tp->ucopy.task)
-		return false;
-
-	if (skb->len <= tcp_hdrlen(skb) &&
-	    skb_queue_len(&tp->ucopy.prequeue) == 0)
-		return false;
-
-	/* Before escaping RCU protected region, we need to take care of skb
-	 * dst. Prequeue is only enabled for established sockets.
-	 * For such sockets, we might need the skb dst only to set sk->sk_rx_dst
-	 * Instead of doing full sk_rx_dst validity here, let's perform
-	 * an optimistic check.
-	 */
-	if (likely(sk->sk_rx_dst))
-		skb_dst_drop(skb);
-	else
-		skb_dst_force_safe(skb);
-
-	__skb_queue_tail(&tp->ucopy.prequeue, skb);
-	tp->ucopy.memory += skb->truesize;
-	if (skb_queue_len(&tp->ucopy.prequeue) >= 32 ||
-	    tp->ucopy.memory + atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) {
-		struct sk_buff *skb1;
-
-		BUG_ON(sock_owned_by_user(sk));
-		__NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPPREQUEUEDROPPED,
-				skb_queue_len(&tp->ucopy.prequeue));
-
-		while ((skb1 = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
-			sk_backlog_rcv(sk, skb1);
-
-		tp->ucopy.memory = 0;
-	} else if (skb_queue_len(&tp->ucopy.prequeue) == 1) {
-		wake_up_interruptible_sync_poll(sk_sleep(sk),
-					   POLLIN | POLLRDNORM | POLLRDBAND);
-		if (!inet_csk_ack_scheduled(sk))
-			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
-						  (3 * tcp_rto_min(sk)) / 4,
-						  TCP_RTO_MAX);
-	}
-	return true;
-}
-EXPORT_SYMBOL(tcp_prequeue);
-
 bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
 {
 	u32 limit = sk->sk_rcvbuf + sk->sk_sndbuf;
@@ -1770,8 +1713,7 @@ process:
 	tcp_segs_in(tcp_sk(sk), skb);
 	ret = 0;
 	if (!sock_owned_by_user(sk)) {
-		if (!tcp_prequeue(sk, skb))
-			ret = tcp_v4_do_rcv(sk, skb);
+		ret = tcp_v4_do_rcv(sk, skb);
 	} else if (tcp_add_backlog(sk, skb)) {
 		goto discard_and_relse;
 	}
@@ -1936,9 +1878,6 @@ void tcp_v4_destroy_sock(struct sock *sk)
 	}
 #endif
 
-	/* Clean prequeue, it must be empty really */
-	__skb_queue_purge(&tp->ucopy.prequeue);
-
 	/* Clean up a referenced TCP bind bucket. */
 	if (inet_csk(sk)->icsk_bind_hash)
 		inet_put_port(sk);
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 0ff83c1637d8..1537b87c657f 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -436,8 +436,6 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 		struct tcp_sock *newtp = tcp_sk(newsk);
 
 		/* Now setup tcp_sock */
-		newtp->pred_flags = 0;
-
 		newtp->rcv_wup = newtp->copied_seq =
 		newtp->rcv_nxt = treq->rcv_isn + 1;
 		newtp->segs_in = 1;
@@ -445,7 +443,6 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 		newtp->snd_sml = newtp->snd_una =
 		newtp->snd_nxt = newtp->snd_up = treq->snt_isn + 1;
 
-		tcp_prequeue_init(newtp);
 		INIT_LIST_HEAD(&newtp->tsq_node);
 
 		tcp_init_wl(newtp, treq->rcv_isn);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 886d874775df..8380464aead1 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -295,9 +295,7 @@ static u16 tcp_select_window(struct sock *sk)
 	/* RFC1323 scaling applied */
 	new_win >>= tp->rx_opt.rcv_wscale;
 
-	/* If we advertise zero window, disable fast path. */
 	if (new_win == 0) {
-		tp->pred_flags = 0;
 		if (old_win)
 			NET_INC_STATS(sock_net(sk),
 				      LINUX_MIB_TCPTOZEROWINDOWADV);
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index c0feeeef962a..f753f9d2fee3 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -239,7 +239,6 @@ static int tcp_write_timeout(struct sock *sk)
 /* Called with BH disabled */
 void tcp_delack_timer_handler(struct sock *sk)
 {
-	struct tcp_sock *tp = tcp_sk(sk);
 	struct inet_connection_sock *icsk = inet_csk(sk);
 
 	sk_mem_reclaim_partial(sk);
@@ -254,17 +253,6 @@ void tcp_delack_timer_handler(struct sock *sk)
 	}
 	icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
 
-	if (!skb_queue_empty(&tp->ucopy.prequeue)) {
-		struct sk_buff *skb;
-
-		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED);
-
-		while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
-			sk_backlog_rcv(sk, skb);
-
-		tp->ucopy.memory = 0;
-	}
-
 	if (inet_csk_ack_scheduled(sk)) {
 		if (!icsk->icsk_ack.pingpong) {
 			/* Delayed ACK missed: inflate ATO. */
diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c
index bec9cafbe3f9..e5de84310949 100644
--- a/net/ipv4/tcp_westwood.c
+++ b/net/ipv4/tcp_westwood.c
@@ -153,24 +153,6 @@ static inline void update_rtt_min(struct westwood *w)
 		w->rtt_min = min(w->rtt, w->rtt_min);
 }
 
-/*
- * @westwood_fast_bw
- * It is called when we are in fast path. In particular it is called when
- * header prediction is successful. In such case in fact update is
- * straight forward and doesn't need any particular care.
- */
-static inline void westwood_fast_bw(struct sock *sk)
-{
-	const struct tcp_sock *tp = tcp_sk(sk);
-	struct westwood *w = inet_csk_ca(sk);
-
-	westwood_update_window(sk);
-
-	w->bk += tp->snd_una - w->snd_una;
-	w->snd_una = tp->snd_una;
-	update_rtt_min(w);
-}
-
 /*
  * @westwood_acked_count
  * This function evaluates cumul_ack for evaluating bk in case of
@@ -223,17 +205,12 @@ static u32 tcp_westwood_bw_rttmin(const struct sock *sk)
 
 static void tcp_westwood_ack(struct sock *sk, u32 ack_flags)
 {
-	if (ack_flags & CA_ACK_SLOWPATH) {
-		struct westwood *w = inet_csk_ca(sk);
+	struct westwood *w = inet_csk_ca(sk);
 
-		westwood_update_window(sk);
-		w->bk += westwood_acked_count(sk);
+	westwood_update_window(sk);
+	w->bk += westwood_acked_count(sk);
 
-		update_rtt_min(w);
-		return;
-	}
-
-	westwood_fast_bw(sk);
+	update_rtt_min(w);
 }
 
 static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 2968a33cca7d..39ee8e7fc4bd 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1505,8 +1505,7 @@ process:
 	tcp_segs_in(tcp_sk(sk), skb);
 	ret = 0;
 	if (!sock_owned_by_user(sk)) {
-		if (!tcp_prequeue(sk, skb))
-			ret = tcp_v6_do_rcv(sk, skb);
+		ret = tcp_v6_do_rcv(sk, skb);
 	} else if (tcp_add_backlog(sk, skb)) {
 		goto discard_and_relse;
 	}