[PATCH 0/17]: tcp & more tcp

[PATCH 0/17]: tcp & more tcp

[Ilpo Järvinen]

Hi,

The first one is the retrans leak fix for net-2.6, rest for
net-next (IMHO).

The series includes two fixes which are a result of my adventure
to measure large window loss recovery performance. I still have
some work to do in that area but the simplest in-order behaviors
now easily scales beyond 1GbE even on a low-end machine :-).

--
 i.

[PATCH net-2.6 01/17] tcp: fix retrans_out leaks

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

There's conflicting assumptions in shifting, the caller assumes
that dupsack results in S'ed skbs (or a part of it) for sure but
never gave a hint to tcp_sacktag_one when dsack is actually in
use. Thus DSACK retrans_out -= pcount was not taken and the
counter became out of sync. Remove obstacle from that information
flow to get DSACKs accounted in tcp_sacktag_one as expected.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Tested-by: Denys Fedoryshchenko <denys@visp.net.lb>
---
 net/ipv4/tcp_input.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a6961d7..c28976a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1374,7 +1374,8 @@ static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
 
 static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
 			   struct tcp_sacktag_state *state,
-			   unsigned int pcount, int shifted, int mss)
+			   unsigned int pcount, int shifted, int mss,
+			   int dup_sack)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *prev = tcp_write_queue_prev(sk, skb);
@@ -1410,7 +1411,7 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
 	}
 
 	/* We discard results */
-	tcp_sacktag_one(skb, sk, state, 0, pcount);
+	tcp_sacktag_one(skb, sk, state, dup_sack, pcount);
 
 	/* Difference in this won't matter, both ACKed by the same cumul. ACK */
 	TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
@@ -1561,7 +1562,7 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
 
 	if (!skb_shift(prev, skb, len))
 		goto fallback;
-	if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss))
+	if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack))
 		goto out;
 
 	/* Hole filled allows collapsing with the next as well, this is very
@@ -1580,7 +1581,7 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
 	len = skb->len;
 	if (skb_shift(prev, skb, len)) {
 		pcount += tcp_skb_pcount(skb);
-		tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss);
+		tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0);
 	}
 
 out:
-- 
1.5.6.5

[PATCH net-next 02/17] tcp: don't backtrack to sacked skbs

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Backtracking to sacked skbs is a horrible performance killer
since the hint cannot be advanced successfully past them...
...And it's totally unnecessary too.

In theory this is 2.6.27..28 regression but I doubt anybody
can make .28 to have worse performance because of other TCP
improvements.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_output.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f6f61b3..2471cd4 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2065,7 +2065,7 @@ begin_fwd:
 			goto begin_fwd;
 
 		} else if (!(sacked & TCPCB_LOST)) {
-			if (hole == NULL && !(sacked & TCPCB_SACKED_RETRANS))
+			if (hole == NULL && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
 				hole = skb;
 			continue;
 
-- 
1.5.6.5

[PATCH net-next 03/17] tcp: fix lost_cnt_hint miscounts

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

It is possible that lost_cnt_hint gets underflow in
tcp_clean_rtx_queue because the cumulative ACK can cover
the segment where lost_skb_hint points to only partially,
which means that the hint is not cleared, opposite to what
my (earlier) comment claimed.

Also I don't agree what I ended up writing about non-trivial
case there to be what I intented to say. It was not supposed
to happen that the hint won't get cleared and we underflow
in any scenario.

In general, this is quite hard to trigger in practice.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_input.c |   13 +++++--------
 1 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c28976a..3f2f090 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3273,18 +3273,15 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 		if (tcp_is_reno(tp)) {
 			tcp_remove_reno_sacks(sk, pkts_acked);
 		} else {
+			int delta;
+
 			/* Non-retransmitted hole got filled? That's reordering */
 			if (reord < prior_fackets)
 				tcp_update_reordering(sk, tp->fackets_out - reord, 0);
 
-			/* No need to care for underflows here because
-			 * the lost_skb_hint gets NULLed if we're past it
-			 * (or something non-trivial happened)
-			 */
-			if (tcp_is_fack(tp))
-				tp->lost_cnt_hint -= pkts_acked;
-			else
-				tp->lost_cnt_hint -= prior_sacked - tp->sacked_out;
+			delta = tcp_is_fack(tp) ? pkts_acked :
+						  prior_sacked - tp->sacked_out;
+			tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta);
 		}
 
 		tp->fackets_out -= min(pkts_acked, tp->fackets_out);
-- 
1.5.6.5

[PATCH net-next 04/17] tcp: deferring in middle of queue makes very little sense

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

If skb can be sent right away, we certainly should do that
if it's in the middle of the queue because it won't get
more data into it.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_output.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 2471cd4..fa3c81a 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1356,6 +1356,10 @@ static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
 	if (limit >= sk->sk_gso_max_size)
 		goto send_now;
 
+	/* Middle in queue won't get any more data, full sendable already? */
+	if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
+		goto send_now;
+
 	if (sysctl_tcp_tso_win_divisor) {
 		u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
 
-- 
1.5.6.5

[PATCH net-next 05/17] tcp: Don't clear hints when tcp_fragmenting

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

1) We didn't remove any skbs, so no need to handle stale refs.

2) scoreboard_skb_hint is trivial, no timestamps were changed
   so no need to clear that one

3) lost_skb_hint needs tweaking similar to that of
   tcp_sacktag_one().

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_output.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index fa3c81a..3feab4d 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -771,7 +771,6 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
 
 	BUG_ON(len > skb->len);
 
-	tcp_clear_retrans_hints_partial(tp);
 	nsize = skb_headlen(skb) - len;
 	if (nsize < 0)
 		nsize = 0;
@@ -854,6 +853,12 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
 			tcp_verify_left_out(tp);
 		}
 		tcp_adjust_fackets_out(sk, skb, diff);
+
+		if (tp->lost_skb_hint &&
+		    before(TCP_SKB_CB(skb)->seq,
+			   TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
+		    (tcp_is_fack(tp) || TCP_SKB_CB(skb)->sacked))
+			tp->lost_cnt_hint -= diff;
 	}
 
 	/* Link BUFF into the send queue. */
-- 
1.5.6.5

[PATCH net-next 06/17] tcp: fix corner case issue in segmentation during rexmitting

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

If cur_mss grew very recently so that the previously G/TSOed skb
now fits well into a single segment it would get send up in
parts unless we calculate # of segments again. This corner-case
could happen eg. after mtu probe completes or less than
previously sack blocks are required for the opposite direction.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_output.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 3feab4d..77af7fa 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1921,6 +1921,8 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 	if (skb->len > cur_mss) {
 		if (tcp_fragment(sk, skb, cur_mss, cur_mss))
 			return -ENOMEM; /* We'll try again later. */
+	} else {
+		tcp_init_tso_segs(sk, skb, cur_mss);
 	}
 
 	tcp_retrans_try_collapse(sk, skb, cur_mss);
-- 
1.5.6.5

[PATCH net-next 07/17] tcp: remove redundant code from tcp_mark_lost_retrans

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Arnd Hannemann <hannemann@nets.rwth-aachen.de> noticed and was
puzzled by the fact that !tcp_is_fack(tp) leads to early return
near the beginning and the later on tcp_is_fack(tp) was still
used in an if condition. The later check was a left-over from
RFC3517 SACK stuff (== !tcp_is_fack(tp) behavior nowadays) as
there wasn't clear way how to handle this particular check
cheaply in the spirit of RFC3517 (using only SACK blocks, not
holes + SACK blocks as with FACK). I sort of left it there as
a reminder but since it's confusing other people just remove
it and comment the missing-feature stuff instead.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Cc: Arnd Hannemann <hannemann@nets.rwth-aachen.de>
---
 net/ipv4/tcp_input.c |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3f2f090..125b451 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1178,10 +1178,18 @@ static void tcp_mark_lost_retrans(struct sock *sk)
 		if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
 			continue;
 
-		if (after(received_upto, ack_seq) &&
-		    (tcp_is_fack(tp) ||
-		     !before(received_upto,
-			     ack_seq + tp->reordering * tp->mss_cache))) {
+		/* TODO: We would like to get rid of tcp_is_fack(tp) only
+		 * constraint here (see above) but figuring out that at
+		 * least tp->reordering SACK blocks reside between ack_seq
+		 * and received_upto is not easy task to do cheaply with
+		 * the available datastructures.
+		 *
+		 * Whether FACK should check here for tp->reordering segs
+		 * in-between one could argue for either way (it would be
+		 * rather simple to implement as we could count fack_count
+		 * during the walk and do tp->fackets_out - fack_count).
+		 */
+		if (after(received_upto, ack_seq)) {
 			TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
 			tp->retrans_out -= tcp_skb_pcount(skb);
 
-- 
1.5.6.5

[PATCH net-next 08/17] tcp: separate timeout marking loop to it's own function

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Some comment about its current state added. So far I have
seen very few cases where the thing is actually useful,
usually just marginally (though admittedly I don't usually
see top of window losses where it seems possible that there
could be some gain), instead, more often the cases suffer
from L-marking spike which is certainly not desirable
(I'll bury improving it to my todo list, but on a low
prio position).

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_input.c |   63 +++++++++++++++++++++++++++++++-------------------
 1 files changed, 39 insertions(+), 24 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 125b451..03f5ede 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2461,6 +2461,44 @@ static int tcp_time_to_recover(struct sock *sk)
 	return 0;
 }
 
+/* New heuristics: it is possible only after we switched to restart timer
+ * each time when something is ACKed. Hence, we can detect timed out packets
+ * during fast retransmit without falling to slow start.
+ *
+ * Usefulness of this as is very questionable, since we should know which of
+ * the segments is the next to timeout which is relatively expensive to find
+ * in general case unless we add some data structure just for that. The
+ * current approach certainly won't find the right one too often and when it
+ * finally does find _something_ it usually marks large part of the window
+ * right away (because a retransmission with a larger timestamp blocks the
+ * loop from advancing). -ij
+ */
+static void tcp_timeout_skbs(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *skb;
+
+	if (!tcp_is_fack(tp) || !tcp_head_timedout(sk))
+		return;
+
+	skb = tp->scoreboard_skb_hint;
+	if (tp->scoreboard_skb_hint == NULL)
+		skb = tcp_write_queue_head(sk);
+
+	tcp_for_write_queue_from(skb, sk) {
+		if (skb == tcp_send_head(sk))
+			break;
+		if (!tcp_skb_timedout(sk, skb))
+			break;
+
+		tcp_skb_mark_lost(tp, skb);
+	}
+
+	tp->scoreboard_skb_hint = skb;
+
+	tcp_verify_left_out(tp);
+}
+
 /* Mark head of queue up as lost. With RFC3517 SACK, the packets is
  * is against sacked "cnt", otherwise it's against facked "cnt"
  */
@@ -2533,30 +2571,7 @@ static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
 		tcp_mark_head_lost(sk, sacked_upto);
 	}
 
-	/* New heuristics: it is possible only after we switched
-	 * to restart timer each time when something is ACKed.
-	 * Hence, we can detect timed out packets during fast
-	 * retransmit without falling to slow start.
-	 */
-	if (tcp_is_fack(tp) && tcp_head_timedout(sk)) {
-		struct sk_buff *skb;
-
-		skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
-			: tcp_write_queue_head(sk);
-
-		tcp_for_write_queue_from(skb, sk) {
-			if (skb == tcp_send_head(sk))
-				break;
-			if (!tcp_skb_timedout(sk, skb))
-				break;
-
-			tcp_skb_mark_lost(tp, skb);
-		}
-
-		tp->scoreboard_skb_hint = skb;
-
-		tcp_verify_left_out(tp);
-	}
+	tcp_timeout_skbs(sk);
 }
 
 /* CWND moderation, preventing bursts due to too big ACKs
-- 
1.5.6.5

[PATCH net-next 09/17] tcp: cleanup ca_state mess in tcp_timer

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Redundant checks made indentation impossible to follow.
However, it might be useful to make this ca_state+is_sack
indexed array.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_timer.c |   23 ++++++++++-------------
 1 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 0170e91..b144a26 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -328,19 +328,16 @@ static void tcp_retransmit_timer(struct sock *sk)
 	if (icsk->icsk_retransmits == 0) {
 		int mib_idx;
 
-		if (icsk->icsk_ca_state == TCP_CA_Disorder ||
-		    icsk->icsk_ca_state == TCP_CA_Recovery) {
-			if (tcp_is_sack(tp)) {
-				if (icsk->icsk_ca_state == TCP_CA_Recovery)
-					mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
-				else
-					mib_idx = LINUX_MIB_TCPSACKFAILURES;
-			} else {
-				if (icsk->icsk_ca_state == TCP_CA_Recovery)
-					mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
-				else
-					mib_idx = LINUX_MIB_TCPRENOFAILURES;
-			}
+		if (icsk->icsk_ca_state == TCP_CA_Disorder) {
+			if (tcp_is_sack(tp))
+				mib_idx = LINUX_MIB_TCPSACKFAILURES;
+			else
+				mib_idx = LINUX_MIB_TCPRENOFAILURES;
+		} else if (icsk->icsk_ca_state == TCP_CA_Recovery) {
+			if (tcp_is_sack(tp))
+				mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
+			else
+				mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
 		} else if (icsk->icsk_ca_state == TCP_CA_Loss) {
 			mib_idx = LINUX_MIB_TCPLOSSFAILURES;
 		} else {
-- 
1.5.6.5

[PATCH net-next 10/17] tcp: drop unnecessary local var in collapse

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_output.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 77af7fa..61445b5 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1767,11 +1767,9 @@ static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
 	int skb_size, next_skb_size;
-	u16 flags;
 
 	skb_size = skb->len;
 	next_skb_size = next_skb->len;
-	flags = TCP_SKB_CB(skb)->flags;
 
 	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
 
@@ -1791,9 +1789,8 @@ static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
 	/* Update sequence range on original skb. */
 	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
 
-	/* Merge over control information. */
-	flags |= TCP_SKB_CB(next_skb)->flags; /* This moves PSH/FIN etc. over */
-	TCP_SKB_CB(skb)->flags = flags;
+	/* Merge over control information. This moves PSH/FIN etc. over */
+	TCP_SKB_CB(skb)->flags |= TCP_SKB_CB(next_skb)->flags;
 
 	/* All done, get rid of second SKB and account for it so
 	 * packet counting does not break.
-- 
1.5.6.5

[PATCH net-next 11/17] htcp: merge icsk_ca_state compare

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Similar to what is done elsewhere in TCP code when double
state checks are being done.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_htcp.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c
index 937549b..9520eec 100644
--- a/net/ipv4/tcp_htcp.c
+++ b/net/ipv4/tcp_htcp.c
@@ -115,8 +115,7 @@ static void measure_achieved_throughput(struct sock *sk, u32 pkts_acked, s32 rtt
 		return;
 
 	/* achieved throughput calculations */
-	if (icsk->icsk_ca_state != TCP_CA_Open &&
-	    icsk->icsk_ca_state != TCP_CA_Disorder) {
+	if (!((1 << icsk->icsk_ca_state) & (TCPF_CA_Open | TCPF_CA_Disorder))) {
 		ca->packetcount = 0;
 		ca->lasttime = now;
 		return;
-- 
1.5.6.5

[PATCH net-next 12/17] tcp: add helper for AI algorithm

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

It seems that implementation in yeah was inconsistent to what
other did as it would increase cwnd one ack earlier than the
others do.

Size benefits:

  bictcp_cong_avoid |  -36
  tcp_cong_avoid_ai |  +52
  bictcp_cong_avoid |  -34
  tcp_scalable_cong_avoid |  -36
  tcp_veno_cong_avoid |  -12
  tcp_yeah_cong_avoid |  -38

= -104 bytes total

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 include/net/tcp.h       |    1 +
 net/ipv4/tcp_bic.c      |   11 +----------
 net/ipv4/tcp_cong.c     |   21 ++++++++++++++-------
 net/ipv4/tcp_cubic.c    |   11 +----------
 net/ipv4/tcp_scalable.c |   10 ++--------
 net/ipv4/tcp_veno.c     |    7 +------
 net/ipv4/tcp_yeah.c     |    9 +--------
 7 files changed, 21 insertions(+), 49 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 218235d..0366a55 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -685,6 +685,7 @@ extern void tcp_get_allowed_congestion_control(char *buf, size_t len);
 extern int tcp_set_allowed_congestion_control(char *allowed);
 extern int tcp_set_congestion_control(struct sock *sk, const char *name);
 extern void tcp_slow_start(struct tcp_sock *tp);
+extern void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w);
 
 extern struct tcp_congestion_ops tcp_init_congestion_ops;
 extern u32 tcp_reno_ssthresh(struct sock *sk);
diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c
index 7eb7636..3b53fd1 100644
--- a/net/ipv4/tcp_bic.c
+++ b/net/ipv4/tcp_bic.c
@@ -149,16 +149,7 @@ static void bictcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
 		tcp_slow_start(tp);
 	else {
 		bictcp_update(ca, tp->snd_cwnd);
-
-		/* In dangerous area, increase slowly.
-		 * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
-		 */
-		if (tp->snd_cwnd_cnt >= ca->cnt) {
-			if (tp->snd_cwnd < tp->snd_cwnd_clamp)
-				tp->snd_cwnd++;
-			tp->snd_cwnd_cnt = 0;
-		} else
-			tp->snd_cwnd_cnt++;
+		tcp_cong_avoid_ai(tp, ca->cnt);
 	}
 
 }
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 4ec5b4e..e92beb9 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -336,6 +336,19 @@ void tcp_slow_start(struct tcp_sock *tp)
 }
 EXPORT_SYMBOL_GPL(tcp_slow_start);
 
+/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w) */
+void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w)
+{
+	if (tp->snd_cwnd_cnt >= w) {
+		if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+			tp->snd_cwnd++;
+		tp->snd_cwnd_cnt = 0;
+	} else {
+		tp->snd_cwnd_cnt++;
+	}
+}
+EXPORT_SYMBOL_GPL(tcp_cong_avoid_ai);
+
 /*
  * TCP Reno congestion control
  * This is special case used for fallback as well.
@@ -365,13 +378,7 @@ void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
 				tp->snd_cwnd++;
 		}
 	} else {
-		/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd */
-		if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
-			if (tp->snd_cwnd < tp->snd_cwnd_clamp)
-				tp->snd_cwnd++;
-			tp->snd_cwnd_cnt = 0;
-		} else
-			tp->snd_cwnd_cnt++;
+		tcp_cong_avoid_ai(tp, tp->snd_cwnd);
 	}
 }
 EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index ee467ec..71d5f2f 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -294,16 +294,7 @@ static void bictcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
 		tcp_slow_start(tp);
 	} else {
 		bictcp_update(ca, tp->snd_cwnd);
-
-		/* In dangerous area, increase slowly.
-		 * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
-		 */
-		if (tp->snd_cwnd_cnt >= ca->cnt) {
-			if (tp->snd_cwnd < tp->snd_cwnd_clamp)
-				tp->snd_cwnd++;
-			tp->snd_cwnd_cnt = 0;
-		} else
-			tp->snd_cwnd_cnt++;
+		tcp_cong_avoid_ai(tp, ca->cnt);
 	}
 
 }
diff --git a/net/ipv4/tcp_scalable.c b/net/ipv4/tcp_scalable.c
index 4660b08..a765137 100644
--- a/net/ipv4/tcp_scalable.c
+++ b/net/ipv4/tcp_scalable.c
@@ -24,14 +24,8 @@ static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
 
 	if (tp->snd_cwnd <= tp->snd_ssthresh)
 		tcp_slow_start(tp);
-	else {
-		tp->snd_cwnd_cnt++;
-		if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){
-			if (tp->snd_cwnd < tp->snd_cwnd_clamp)
-				tp->snd_cwnd++;
-			tp->snd_cwnd_cnt = 0;
-		}
-	}
+	else
+		tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT));
 }
 
 static u32 tcp_scalable_ssthresh(struct sock *sk)
diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c
index d08b2e8..e9bbff7 100644
--- a/net/ipv4/tcp_veno.c
+++ b/net/ipv4/tcp_veno.c
@@ -159,12 +159,7 @@ static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
 				/* In the "non-congestive state", increase cwnd
 				 *  every rtt.
 				 */
-				if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
-					if (tp->snd_cwnd < tp->snd_cwnd_clamp)
-						tp->snd_cwnd++;
-					tp->snd_cwnd_cnt = 0;
-				} else
-					tp->snd_cwnd_cnt++;
+				tcp_cong_avoid_ai(tp, tp->snd_cwnd);
 			} else {
 				/* In the "congestive state", increase cwnd
 				 * every other rtt.
diff --git a/net/ipv4/tcp_yeah.c b/net/ipv4/tcp_yeah.c
index 9ec843a..66b6821 100644
--- a/net/ipv4/tcp_yeah.c
+++ b/net/ipv4/tcp_yeah.c
@@ -94,14 +94,7 @@ static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
 
 	} else {
 		/* Reno */
-
-		if (tp->snd_cwnd_cnt < tp->snd_cwnd)
-			tp->snd_cwnd_cnt++;
-
-		if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
-			tp->snd_cwnd++;
-			tp->snd_cwnd_cnt = 0;
-		}
+		tcp_cong_avoid_ai(tp, tp->snd_cwnd);
 	}
 
 	/* The key players are v_vegas.beg_snd_una and v_beg_snd_nxt.
-- 
1.5.6.5

[PATCH net-next 13/17] tcp: kill eff_sacks "cache", the sole user can calculate itself

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Also fixes insignificant bug that would cause sending of stale
SACK block (would occur in some corner cases).

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 include/linux/tcp.h      |    1 -
 include/net/tcp.h        |    1 -
 net/ipv4/tcp_input.c     |   15 ++-------------
 net/ipv4/tcp_minisocks.c |    3 +--
 net/ipv4/tcp_output.c    |   12 ++++++------
 5 files changed, 9 insertions(+), 23 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 0cd99e6..4b86ad7 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -218,7 +218,6 @@ struct tcp_options_received {
 		snd_wscale : 4,	/* Window scaling received from sender	*/
 		rcv_wscale : 4;	/* Window scaling to send to receiver	*/
 /*	SACKs data	*/
-	u8	eff_sacks;	/* Size of SACK array to send with next packet */
 	u8	num_sacks;	/* Number of SACK blocks		*/
 	u16	user_mss;  	/* mss requested by user in ioctl */
 	u16	mss_clamp;	/* Maximal mss, negotiated at connection setup */
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 0366a55..055e494 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -926,7 +926,6 @@ extern void tcp_done(struct sock *sk);
 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
 {
 	rx_opt->dsack = 0;
-	rx_opt->eff_sacks = 0;
 	rx_opt->num_sacks = 0;
 }
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 03f5ede..e4442a2 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4099,7 +4099,6 @@ static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq)
 		tp->rx_opt.dsack = 1;
 		tp->duplicate_sack[0].start_seq = seq;
 		tp->duplicate_sack[0].end_seq = end_seq;
-		tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks + 1;
 	}
 }
 
@@ -4154,8 +4153,6 @@ static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
 			 * Decrease num_sacks.
 			 */
 			tp->rx_opt.num_sacks--;
-			tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks +
-					       tp->rx_opt.dsack;
 			for (i = this_sack; i < tp->rx_opt.num_sacks; i++)
 				sp[i] = sp[i + 1];
 			continue;
@@ -4218,7 +4215,6 @@ new_sack:
 	sp->start_seq = seq;
 	sp->end_seq = end_seq;
 	tp->rx_opt.num_sacks++;
-	tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
 }
 
 /* RCV.NXT advances, some SACKs should be eaten. */
@@ -4232,7 +4228,6 @@ static void tcp_sack_remove(struct tcp_sock *tp)
 	/* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
 	if (skb_queue_empty(&tp->out_of_order_queue)) {
 		tp->rx_opt.num_sacks = 0;
-		tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
 		return;
 	}
 
@@ -4253,11 +4248,8 @@ static void tcp_sack_remove(struct tcp_sock *tp)
 		this_sack++;
 		sp++;
 	}
-	if (num_sacks != tp->rx_opt.num_sacks) {
+	if (num_sacks != tp->rx_opt.num_sacks)
 		tp->rx_opt.num_sacks = num_sacks;
-		tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks +
-				       tp->rx_opt.dsack;
-	}
 }
 
 /* This one checks to see if we can put data from the
@@ -4333,10 +4325,8 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 
 	TCP_ECN_accept_cwr(tp, skb);
 
-	if (tp->rx_opt.dsack) {
+	if (tp->rx_opt.dsack)
 		tp->rx_opt.dsack = 0;
-		tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks;
-	}
 
 	/*  Queue data for delivery to the user.
 	 *  Packets in sequence go to the receive queue.
@@ -4456,7 +4446,6 @@ drop:
 		if (tcp_is_sack(tp)) {
 			tp->rx_opt.num_sacks = 1;
 			tp->rx_opt.dsack     = 0;
-			tp->rx_opt.eff_sacks = 1;
 			tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
 			tp->selective_acks[0].end_seq =
 						TCP_SKB_CB(skb)->end_seq;
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index f67effb..bb3d8b3 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -434,9 +434,8 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
 		newtp->rx_opt.saw_tstamp = 0;
 
 		newtp->rx_opt.dsack = 0;
-		newtp->rx_opt.eff_sacks = 0;
-
 		newtp->rx_opt.num_sacks = 0;
+
 		newtp->urg_data = 0;
 
 		if (sock_flag(newsk, SOCK_KEEPOPEN))
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 61445b5..1555bb7 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -441,10 +441,8 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
 			*ptr++ = htonl(sp[this_sack].end_seq);
 		}
 
-		if (tp->rx_opt.dsack) {
+		if (tp->rx_opt.dsack)
 			tp->rx_opt.dsack = 0;
-			tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks;
-		}
 	}
 }
 
@@ -550,6 +548,7 @@ static unsigned tcp_established_options(struct sock *sk, struct sk_buff *skb,
 	struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL;
 	struct tcp_sock *tp = tcp_sk(sk);
 	unsigned size = 0;
+	unsigned int eff_sacks;
 
 #ifdef CONFIG_TCP_MD5SIG
 	*md5 = tp->af_specific->md5_lookup(sk, sk);
@@ -568,10 +567,11 @@ static unsigned tcp_established_options(struct sock *sk, struct sk_buff *skb,
 		size += TCPOLEN_TSTAMP_ALIGNED;
 	}
 
-	if (unlikely(tp->rx_opt.eff_sacks)) {
+	eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
+	if (unlikely(eff_sacks)) {
 		const unsigned remaining = MAX_TCP_OPTION_SPACE - size;
 		opts->num_sack_blocks =
-			min_t(unsigned, tp->rx_opt.eff_sacks,
+			min_t(unsigned, eff_sacks,
 			      (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
 			      TCPOLEN_SACK_PERBLOCK);
 		size += TCPOLEN_SACK_BASE_ALIGNED +
@@ -1418,7 +1418,7 @@ static int tcp_mtu_probe(struct sock *sk)
 	    icsk->icsk_mtup.probe_size ||
 	    inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
 	    tp->snd_cwnd < 11 ||
-	    tp->rx_opt.eff_sacks)
+	    tp->rx_opt.num_sacks || tp->rx_opt.dsack)
 		return -1;
 
 	/* Very simple search strategy: just double the MSS. */
-- 
1.5.6.5

[PATCH net-next 14/17] tcp: remove pointless .dsack code

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

In the pure assignment case, the earlier zeroing is
still in effect.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_input.c  |    4 +---
 net/ipv4/tcp_output.c |    3 +--
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index e4442a2..464c8a4 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4325,8 +4325,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 
 	TCP_ECN_accept_cwr(tp, skb);
 
-	if (tp->rx_opt.dsack)
-		tp->rx_opt.dsack = 0;
+	tp->rx_opt.dsack = 0;
 
 	/*  Queue data for delivery to the user.
 	 *  Packets in sequence go to the receive queue.
@@ -4445,7 +4444,6 @@ drop:
 		/* Initial out of order segment, build 1 SACK. */
 		if (tcp_is_sack(tp)) {
 			tp->rx_opt.num_sacks = 1;
-			tp->rx_opt.dsack     = 0;
 			tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
 			tp->selective_acks[0].end_seq =
 						TCP_SKB_CB(skb)->end_seq;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 1555bb7..d5c7245 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -441,8 +441,7 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
 			*ptr++ = htonl(sp[this_sack].end_seq);
 		}
 
-		if (tp->rx_opt.dsack)
-			tp->rx_opt.dsack = 0;
+		tp->rx_opt.dsack = 0;
 	}
 }
 
-- 
1.5.6.5

[PATCH net-next 15/17] tcp: kill pointless if () in sack_remove

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_input.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 464c8a4..071917d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4248,8 +4248,7 @@ static void tcp_sack_remove(struct tcp_sock *tp)
 		this_sack++;
 		sp++;
 	}
-	if (num_sacks != tp->rx_opt.num_sacks)
-		tp->rx_opt.num_sacks = num_sacks;
+	tp->rx_opt.num_sacks = num_sacks;
 }
 
 /* This one checks to see if we can put data from the
-- 
1.5.6.5

[PATCH net-next 16/17] tcp: in sendmsg/pages open code the real goto target

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

copied was assigned zero right before the goto, so if (copied)
cannot ever be true.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 90b2f3c..d3f9bee 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -683,7 +683,7 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffse
 
 	err = -EPIPE;
 	if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
-		goto do_error;
+		goto out_err;
 
 	while (psize > 0) {
 		struct sk_buff *skb = tcp_write_queue_tail(sk);
@@ -854,7 +854,7 @@ int tcp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
 
 	err = -EPIPE;
 	if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
-		goto do_error;
+		goto out_err;
 
 	while (--iovlen >= 0) {
 		int seglen = iov->iov_len;
-- 
1.5.6.5

[PATCH net-next 17/17] tcp: get rid of two unnecessary u16s in TCP skb flags copying

[Ilpo Järvinen]

From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

I guess these fields were one day 16-bit in the struct but
nowadays they're just using 8 bits anyway.

This is just a precaution, didn't result any change in my
case but who knows what all those varying gcc versions &
options do. I've been told that 16-bit is not so nice with
some cpus.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_output.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index d5c7245..274110e 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -766,7 +766,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
 	struct sk_buff *buff;
 	int nsize, old_factor;
 	int nlen;
-	u16 flags;
+	u8 flags;
 
 	BUG_ON(len > skb->len);
 
@@ -1281,7 +1281,7 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
 {
 	struct sk_buff *buff;
 	int nlen = skb->len - len;
-	u16 flags;
+	u8 flags;
 
 	/* All of a TSO frame must be composed of paged data.  */
 	if (skb->len != skb->data_len)
-- 
1.5.6.5

Re: [PATCH net-next 17/17] tcp: get rid of two unnecessary u16s in TCP skb flags copying

[Andi Kleen]

"Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi> writes:

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
>
> I guess these fields were one day 16-bit in the struct but
> nowadays they're just using 8 bits anyway.
>
> This is just a precaution, didn't result any change in my
> case but who knows what all those varying gcc versions &
> options do. I've been told that 16-bit is not so nice with
> some cpus.

Typically when 16bit is not nice, 8bit isn't nice either.
For general flags the most save in terms of uniform performance
is "int"

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only.

Re: [PATCH net-next 17/17] tcp: get rid of two unnecessary u16s in TCP skb flags copying

[David Miller]

From: Andi Kleen <andi@firstfloor.org>
Date: Sun, 01 Mar 2009 03:39:02 +0100

> "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi> writes:
> 
> > From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> >
> > I guess these fields were one day 16-bit in the struct but
> > nowadays they're just using 8 bits anyway.
> >
> > This is just a precaution, didn't result any change in my
> > case but who knows what all those varying gcc versions &
> > options do. I've been told that 16-bit is not so nice with
> > some cpus.
> 
> Typically when 16bit is not nice, 8bit isn't nice either.
> For general flags the most save in terms of uniform performance
> is "int"

It's really only the truly ancient alpha cpus where this is
a measurable issue.  Those chips only have 32-bit loads
and stores, so ever sub-32-bit access involves a 32-bit
load/store and a bunch of byte extraction instructions.

I don't think it's a relevant concern today.  Especially
on x86 if that's why you are alluding to Andi.

Re: [PATCH net-next 17/17] tcp: get rid of two unnecessary u16s in TCP skb flags copying

[Andi Kleen]

On Sat, Feb 28, 2009 at 07:08:45PM -0800, David Miller wrote:
> From: Andi Kleen <andi@firstfloor.org>
> Date: Sun, 01 Mar 2009 03:39:02 +0100
> 
> > "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi> writes:
> > 
> > > From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> > >
> > > I guess these fields were one day 16-bit in the struct but
> > > nowadays they're just using 8 bits anyway.
> > >
> > > This is just a precaution, didn't result any change in my
> > > case but who knows what all those varying gcc versions &
> > > options do. I've been told that 16-bit is not so nice with
> > > some cpus.
> > 
> > Typically when 16bit is not nice, 8bit isn't nice either.
> > For general flags the most save in terms of uniform performance
> > is "int"
> 
> It's really only the truly ancient alpha cpus where this is
> a measurable issue.  Those chips only have 32-bit loads
> and stores, so ever sub-32-bit access involves a 32-bit
> load/store and a bunch of byte extraction instructions.

Yes old Alpha is the only one I know, although I don't claim to know every 
weirdness of every embedded CPU out there.

My point was merely that 16bit is not in any way better than 8 bit.
> 
> I don't think it's a relevant concern today.  Especially
> on x86 if that's why you are alluding to Andi.

x86 normally[1] doesn't care, but it also doesn't save anything normally
for a on stack (or in register) variable because there's typically
padding anyways.

[1] there are some issues on older Intel CPUs with partial register
stall in a few cases.

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only.

Re: [PATCH net-next 17/17] tcp: get rid of two unnecessary u16s in TCP skb flags copying

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:42 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> I guess these fields were one day 16-bit in the struct but
> nowadays they're just using 8 bits anyway.
> 
> This is just a precaution, didn't result any change in my
> case but who knows what all those varying gcc versions &
> options do. I've been told that 16-bit is not so nice with
> some cpus.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-next 16/17] tcp: in sendmsg/pages open code the real goto target

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:41 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> copied was assigned zero right before the goto, so if (copied)
> cannot ever be true.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-next 15/17] tcp: kill pointless if () in sack_remove

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:40 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

I skipped this for the same reason I skipped patch #14.
This could be there to avoid dirtying that part of
the structure when it isn't necessary.

Re: [PATCH net-next 14/17] tcp: remove pointless .dsack code

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:39 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> In the pure assignment case, the earlier zeroing is
> still in effect.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

I skipped this one.

These tests could be there to avoid dirtying a cacheline
when unnecessary.  And so unless we can prove the condition
always hits and we always do the write, we should keep
the tests there.

Re: [PATCH net-next 14/17] tcp: remove pointless .dsack code

[Ilpo Järvinen]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 1061 bytes --]

On Mon, 2 Mar 2009, David Miller wrote:

> From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
> Date: Sat, 28 Feb 2009 16:44:39 +0200
> 
> > From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> > 
> > In the pure assignment case, the earlier zeroing is
> > still in effect.
> > 
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> I skipped this one.
> 
> These tests could be there to avoid dirtying a cacheline
> when unnecessary.  And so unless we can prove the condition
> always hits and we always do the write, we should keep
> the tests there.

We'll be dirty it anyway (not that I check), the first "real" statement
in tcp_rcv_established is:

	tp->rx_opt.saw_tstamp = 0;

...that'll land on the same dword. :-/

I suppose the blocks are there just because they had more complexity 
inside when they had to calculate the eff_sacks too (maybe it would
have been better to just remove them in that drop-patch so you would
have had less head-ache :-)).

Besides, it isn't very nice to have tx/rx or rx'es on different cpus 
anyway, no? 


-- 
 i.

Re: [PATCH net-next 14/17] tcp: remove pointless .dsack code

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Mon, 2 Mar 2009 13:54:17 +0200 (EET)

> We'll be dirty it anyway (not that I check), the first "real" statement
> in tcp_rcv_established is:
> 
> 	tp->rx_opt.saw_tstamp = 0;
> 
> ...that'll land on the same dword. :-/
> 
> I suppose the blocks are there just because they had more complexity 
> inside when they had to calculate the eff_sacks too (maybe it would
> have been better to just remove them in that drop-patch so you would
> have had less head-ache :-)).

That sounds like a good commit log entry for when you resubmit
this patch :-)

Re: [PATCH net-next 13/17] tcp: kill eff_sacks "cache", the sole user can calculate itself

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:38 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> Also fixes insignificant bug that would cause sending of stale
> SACK block (would occur in some corner cases).
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-next 12/17] tcp: add helper for AI algorithm

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:37 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> It seems that implementation in yeah was inconsistent to what
> other did as it would increase cwnd one ack earlier than the
> others do.
> 
> Size benefits:
> 
>   bictcp_cong_avoid |  -36
>   tcp_cong_avoid_ai |  +52
>   bictcp_cong_avoid |  -34
>   tcp_scalable_cong_avoid |  -36
>   tcp_veno_cong_avoid |  -12
>   tcp_yeah_cong_avoid |  -38
> 
> = -104 bytes total
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied, nice work.

Re: [PATCH net-next 11/17] htcp: merge icsk_ca_state compare

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:36 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> Similar to what is done elsewhere in TCP code when double
> state checks are being done.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-next 10/17] tcp: drop unnecessary local var in collapse

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:35 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-next 09/17] tcp: cleanup ca_state mess in tcp_timer

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:34 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> Redundant checks made indentation impossible to follow.
> However, it might be useful to make this ca_state+is_sack
> indexed array.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-next 08/17] tcp: separate timeout marking loop to it's own function

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:33 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> Some comment about its current state added. So far I have
> seen very few cases where the thing is actually useful,
> usually just marginally (though admittedly I don't usually
> see top of window losses where it seems possible that there
> could be some gain), instead, more often the cases suffer
> from L-marking spike which is certainly not desirable
> (I'll bury improving it to my todo list, but on a low
> prio position).
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-next 06/17] tcp: fix corner case issue in segmentation during rexmitting

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:31 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> If cur_mss grew very recently so that the previously G/TSOed skb
> now fits well into a single segment it would get send up in
> parts unless we calculate # of segments again. This corner-case
> could happen eg. after mtu probe completes or less than
> previously sack blocks are required for the opposite direction.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-next 07/17] tcp: remove redundant code from tcp_mark_lost_retrans

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:32 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> Arnd Hannemann <hannemann@nets.rwth-aachen.de> noticed and was
> puzzled by the fact that !tcp_is_fack(tp) leads to early return
> near the beginning and the later on tcp_is_fack(tp) was still
> used in an if condition. The later check was a left-over from
> RFC3517 SACK stuff (== !tcp_is_fack(tp) behavior nowadays) as
> there wasn't clear way how to handle this particular check
> cheaply in the spirit of RFC3517 (using only SACK blocks, not
> holes + SACK blocks as with FACK). I sort of left it there as
> a reminder but since it's confusing other people just remove
> it and comment the missing-feature stuff instead.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-next 05/17] tcp: Don't clear hints when tcp_fragmenting

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:30 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> 1) We didn't remove any skbs, so no need to handle stale refs.
> 
> 2) scoreboard_skb_hint is trivial, no timestamps were changed
>    so no need to clear that one
> 
> 3) lost_skb_hint needs tweaking similar to that of
>    tcp_sacktag_one().
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-next 04/17] tcp: deferring in middle of queue makes very little sense

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:29 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> If skb can be sent right away, we certainly should do that
> if it's in the middle of the queue because it won't get
> more data into it.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

I can't believe this check was missing :-)

Re: [PATCH net-next 03/17] tcp: fix lost_cnt_hint miscounts

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:28 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> It is possible that lost_cnt_hint gets underflow in
> tcp_clean_rtx_queue because the cumulative ACK can cover
> the segment where lost_skb_hint points to only partially,
> which means that the hint is not cleared, opposite to what
> my (earlier) comment claimed.
> 
> Also I don't agree what I ended up writing about non-trivial
> case there to be what I intented to say. It was not supposed
> to happen that the hint won't get cleared and we underflow
> in any scenario.
> 
> In general, this is quite hard to trigger in practice.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-next 02/17] tcp: don't backtrack to sacked skbs

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:27 +0200

> From: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> Backtracking to sacked skbs is a horrible performance killer
> since the hint cannot be advanced successfully past them...
> ...And it's totally unnecessary too.
> 
> In theory this is 2.6.27..28 regression but I doubt anybody
> can make .28 to have worse performance because of other TCP
> improvements.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

Applied.

Re: [PATCH net-2.6 01/17] tcp: fix retrans_out leaks

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 28 Feb 2009 16:44:26 +0200

> There's conflicting assumptions in shifting, the caller assumes
> that dupsack results in S'ed skbs (or a part of it) for sure but
> never gave a hint to tcp_sacktag_one when dsack is actually in
> use. Thus DSACK retrans_out -= pcount was not taken and the
> counter became out of sync. Remove obstacle from that information
> flow to get DSACKs accounted in tcp_sacktag_one as expected.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> Tested-by: Denys Fedoryshchenko <denys@visp.net.lb>

Applied, thanks.