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Commit a1197f5a authored by Ilpo Järvinen's avatar Ilpo Järvinen Committed by David S. Miller
Browse files

tcp: introduce struct tcp_sacktag_state to reduce arg pressure 



There are just too many args to some sacktag functions. This
idea was first proposed by David S. Miller around a year ago,
and the current situation is much worse that what it was back
then.

tcp_sacktag_one can be made a bit simpler by returning the
new sacked (it can be achieved with a single variable though
the previous code "caching" sacked into a local variable and
therefore it is not exactly equal but the results will be the
same).

codiff on x86_64
  tcp_sacktag_one         |  -15
  tcp_shifted_skb         |  -50
  tcp_match_skb_to_sack   |   -1
  tcp_sacktag_walk        |  -64
  tcp_sacktag_write_queue |  -59
  tcp_urg                 |   +1
  tcp_event_data_recv     |   -1
 7 functions changed, 1 bytes added, 190 bytes removed, diff: -189

Signed-off-by: default avatarIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 775ffabf

net/ipv4/tcp_input.c

+74 −71
Original line number Diff line number Diff line
@@ -1237,6 +1237,12 @@ static int tcp_check_dsack(struct sock *sk, struct sk_buff *ack_skb, 
	return dup_sack;

}



struct tcp_sacktag_state {

	int reord;

	int fack_count;

	int flag;

};



/* Check if skb is fully within the SACK block. In presence of GSO skbs,

 * the incoming SACK may not exactly match but we can find smaller MSS

 * aligned portion of it that matches. Therefore we might need to fragment
@@ -1290,25 +1296,25 @@ static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, 
	return in_sack;

}



static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,

			   int *reord, int dup_sack, int fack_count,

			   u8 *sackedto, int pcount)

static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,

			  struct tcp_sacktag_state *state,

			  int dup_sack, int pcount)

{

	struct tcp_sock *tp = tcp_sk(sk);

	u8 sacked = TCP_SKB_CB(skb)->sacked;

	int flag = 0;

	int fack_count = state->fack_count;



	/* Account D-SACK for retransmitted packet. */

	if (dup_sack && (sacked & TCPCB_RETRANS)) {

		if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))

			tp->undo_retrans--;

		if (sacked & TCPCB_SACKED_ACKED)

			*reord = min(fack_count, *reord);

			state->reord = min(fack_count, state->reord);

	}



	/* Nothing to do; acked frame is about to be dropped (was ACKed). */

	if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))

		return flag;

		return sacked;



	if (!(sacked & TCPCB_SACKED_ACKED)) {

		if (sacked & TCPCB_SACKED_RETRANS) {
@@ -1317,7 +1323,7 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk, 
			 * that retransmission is still in flight.

			 */

			if (sacked & TCPCB_LOST) {

				*sackedto &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);

				sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);

				tp->lost_out -= pcount;

				tp->retrans_out -= pcount;

			}
@@ -1328,21 +1334,22 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk, 
				 */

				if (before(TCP_SKB_CB(skb)->seq,

					   tcp_highest_sack_seq(tp)))

					*reord = min(fack_count, *reord);

					state->reord = min(fack_count,

							   state->reord);



				/* SACK enhanced F-RTO (RFC4138; Appendix B) */

				if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))

					flag |= FLAG_ONLY_ORIG_SACKED;

					state->flag |= FLAG_ONLY_ORIG_SACKED;

			}



			if (sacked & TCPCB_LOST) {

				*sackedto &= ~TCPCB_LOST;

				sacked &= ~TCPCB_LOST;

				tp->lost_out -= pcount;

			}

		}



		*sackedto |= TCPCB_SACKED_ACKED;

		flag |= FLAG_DATA_SACKED;

		sacked |= TCPCB_SACKED_ACKED;

		state->flag |= FLAG_DATA_SACKED;

		tp->sacked_out += pcount;



		fack_count += pcount;
@@ -1361,21 +1368,20 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk, 
	 * frames and clear it. undo_retrans is decreased above, L|R frames

	 * are accounted above as well.

	 */

	if (dup_sack && (*sackedto & TCPCB_SACKED_RETRANS)) {

		*sackedto &= ~TCPCB_SACKED_RETRANS;

	if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) {

		sacked &= ~TCPCB_SACKED_RETRANS;

		tp->retrans_out -= pcount;

	}



	return flag;

	return sacked;

}



static int tcp_shifted_skb(struct sock *sk, struct sk_buff *prev,

			   struct sk_buff *skb, unsigned int pcount,

			   int shifted, int fack_count, int *reord,

			   int *flag, int mss)

			   struct sk_buff *skb,

			   struct tcp_sacktag_state *state,

			   unsigned int pcount, int shifted, int mss)

{

	struct tcp_sock *tp = tcp_sk(sk);

	u8 dummy_sacked = TCP_SKB_CB(skb)->sacked;	/* We discard results */



	BUG_ON(!pcount);
@@ -1407,8 +1413,8 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *prev, 
		skb_shinfo(skb)->gso_type = 0;

	}



	*flag |= tcp_sacktag_one(skb, sk, reord, 0, fack_count, &dummy_sacked,

				 pcount);

	/* We discard results */

	tcp_sacktag_one(skb, sk, state, 0, 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);
@@ -1460,9 +1466,9 @@ static int skb_can_shift(struct sk_buff *skb) 
 * skb.

 */

static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,

					  struct tcp_sacktag_state *state,

					  u32 start_seq, u32 end_seq,

					  int dup_sack, int *fack_count,

					  int *reord, int *flag)

					  int dup_sack)

{

	struct tcp_sock *tp = tcp_sk(sk);

	struct sk_buff *prev;
@@ -1559,8 +1565,7 @@ 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, prev, skb, pcount, len, *fack_count, reord,

			     flag, mss))

	if (!tcp_shifted_skb(sk, prev, skb, state, pcount, len, mss))

		goto out;



	/* Hole filled allows collapsing with the next as well, this is very
@@ -1579,12 +1584,12 @@ 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, prev, skb, tcp_skb_pcount(skb), len,

				*fack_count, reord, flag, mss);

		tcp_shifted_skb(sk, prev, skb, state, tcp_skb_pcount(skb), len,

				mss);

	}



out:

	*fack_count += pcount;

	state->fack_count += pcount;

	return prev;



noop:
@@ -1597,9 +1602,9 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, 


static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,

					struct tcp_sack_block *next_dup,

					struct tcp_sacktag_state *state,

					u32 start_seq, u32 end_seq,

					int dup_sack_in, int *fack_count,

					int *reord, int *flag)

					int dup_sack_in)

{

	struct tcp_sock *tp = tcp_sk(sk);

	struct sk_buff *tmp;
@@ -1629,9 +1634,8 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, 
		 * so not even _safe variant of the loop is enough.

		 */

		if (in_sack <= 0) {

			tmp = tcp_shift_skb_data(sk, skb, start_seq,

						 end_seq, dup_sack,

						 fack_count, reord, flag);

			tmp = tcp_shift_skb_data(sk, skb, state,

						 start_seq, end_seq, dup_sack);

			if (tmp != NULL) {

				if (tmp != skb) {

					skb = tmp;
@@ -1650,9 +1654,9 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, 
			break;



		if (in_sack) {

			*flag |= tcp_sacktag_one(skb, sk, reord, dup_sack,

						 *fack_count,

						 &(TCP_SKB_CB(skb)->sacked),

			TCP_SKB_CB(skb)->sacked = tcp_sacktag_one(skb, sk,

								  state,

								  dup_sack,

								  tcp_skb_pcount(skb));



			if (!before(TCP_SKB_CB(skb)->seq,
@@ -1660,7 +1664,7 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, 
				tcp_advance_highest_sack(sk, skb);

		}



		*fack_count += tcp_skb_pcount(skb);

		state->fack_count += tcp_skb_pcount(skb);

	}

	return skb;

}
@@ -1669,7 +1673,8 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, 
 * a normal way

 */

static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,

					u32 skip_to_seq, int *fack_count)

					struct tcp_sacktag_state *state,

					u32 skip_to_seq)

{

	tcp_for_write_queue_from(skb, sk) {

		if (skb == tcp_send_head(sk))
@@ -1678,7 +1683,7 @@ static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, 
		if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq))

			break;



		*fack_count += tcp_skb_pcount(skb);

		state->fack_count += tcp_skb_pcount(skb);

	}

	return skb;

}
@@ -1686,18 +1691,17 @@ static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, 
static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,

						struct sock *sk,

						struct tcp_sack_block *next_dup,

						u32 skip_to_seq,

						int *fack_count, int *reord,

						int *flag)

						struct tcp_sacktag_state *state,

						u32 skip_to_seq)

{

	if (next_dup == NULL)

		return skb;



	if (before(next_dup->start_seq, skip_to_seq)) {

		skb = tcp_sacktag_skip(skb, sk, next_dup->start_seq, fack_count);

		skb = tcp_sacktag_walk(skb, sk, NULL,

		skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq);

		skb = tcp_sacktag_walk(skb, sk, NULL, state,

				       next_dup->start_seq, next_dup->end_seq,

				     1, fack_count, reord, flag);

				       1);

	}



	return skb;
@@ -1719,16 +1723,17 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 
	struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);

	struct tcp_sack_block sp[TCP_NUM_SACKS];

	struct tcp_sack_block *cache;

	struct tcp_sacktag_state state;

	struct sk_buff *skb;

	int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);

	int used_sacks;

	int reord = tp->packets_out;

	int flag = 0;

	int found_dup_sack = 0;

	int fack_count;

	int i, j;

	int first_sack_index;



	state.flag = 0;

	state.reord = tp->packets_out;



	if (!tp->sacked_out) {

		if (WARN_ON(tp->fackets_out))

			tp->fackets_out = 0;
@@ -1738,7 +1743,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 
	found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire,

					 num_sacks, prior_snd_una);

	if (found_dup_sack)

		flag |= FLAG_DSACKING_ACK;

		state.flag |= FLAG_DSACKING_ACK;



	/* Eliminate too old ACKs, but take into

	 * account more or less fresh ones, they can
@@ -1807,7 +1812,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 
	}



	skb = tcp_write_queue_head(sk);

	fack_count = 0;

	state.fack_count = 0;

	i = 0;



	if (!tp->sacked_out) {
@@ -1832,7 +1837,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 


		/* Event "B" in the comment above. */

		if (after(end_seq, tp->high_seq))

			flag |= FLAG_DATA_LOST;

			state.flag |= FLAG_DATA_LOST;



		/* Skip too early cached blocks */

		while (tcp_sack_cache_ok(tp, cache) &&
@@ -1845,13 +1850,13 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 


			/* Head todo? */

			if (before(start_seq, cache->start_seq)) {

				skb = tcp_sacktag_skip(skb, sk, start_seq,

						       &fack_count);

				skb = tcp_sacktag_skip(skb, sk, &state,

						       start_seq);

				skb = tcp_sacktag_walk(skb, sk, next_dup,

						       &state,

						       start_seq,

						       cache->start_seq,

						       dup_sack, &fack_count,

						       &reord, &flag);

						       dup_sack);

			}



			/* Rest of the block already fully processed? */
@@ -1859,9 +1864,8 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 
				goto advance_sp;



			skb = tcp_maybe_skipping_dsack(skb, sk, next_dup,

						       cache->end_seq,

						       &fack_count, &reord,

						       &flag);

						       &state,

						       cache->end_seq);



			/* ...tail remains todo... */

			if (tcp_highest_sack_seq(tp) == cache->end_seq) {
@@ -1869,13 +1873,12 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 
				skb = tcp_highest_sack(sk);

				if (skb == NULL)

					break;

				fack_count = tp->fackets_out;

				state.fack_count = tp->fackets_out;

				cache++;

				goto walk;

			}



			skb = tcp_sacktag_skip(skb, sk, cache->end_seq,

					       &fack_count);

			skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq);

			/* Check overlap against next cached too (past this one already) */

			cache++;

			continue;
@@ -1885,20 +1888,20 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 
			skb = tcp_highest_sack(sk);

			if (skb == NULL)

				break;

			fack_count = tp->fackets_out;

			state.fack_count = tp->fackets_out;

		}

		skb = tcp_sacktag_skip(skb, sk, start_seq, &fack_count);

		skb = tcp_sacktag_skip(skb, sk, &state, start_seq);



walk:

		skb = tcp_sacktag_walk(skb, sk, next_dup, start_seq, end_seq,

				       dup_sack, &fack_count, &reord, &flag);

		skb = tcp_sacktag_walk(skb, sk, next_dup, &state,

				       start_seq, end_seq, dup_sack);



advance_sp:

		/* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct

		 * due to in-order walk

		 */

		if (after(end_seq, tp->frto_highmark))

			flag &= ~FLAG_ONLY_ORIG_SACKED;

			state.flag &= ~FLAG_ONLY_ORIG_SACKED;



		i++;

	}
@@ -1915,10 +1918,10 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 


	tcp_verify_left_out(tp);



	if ((reord < tp->fackets_out) &&

	if ((state.reord < tp->fackets_out) &&

	    ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) &&

	    (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))

		tcp_update_reordering(sk, tp->fackets_out - reord, 0);

		tcp_update_reordering(sk, tp->fackets_out - state.reord, 0);



out:
@@ -1928,7 +1931,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 
	WARN_ON((int)tp->retrans_out < 0);

	WARN_ON((int)tcp_packets_in_flight(tp) < 0);

#endif

	return flag;

	return state.flag;

}



/* Limits sacked_out so that sum with lost_out isn't ever larger than