diff mbox series

[net-next,v3,20/21] rxrpc: Clean up the resend algorithm

Message ID 20240306000655.1100294-21-dhowells@redhat.com (mailing list archive)
State Accepted
Commit 37473e41623409286ab2f5db628a59d4da9a79d7
Delegated to: Netdev Maintainers
Headers show
Series rxrpc: Miscellaneous changes and make use of MSG_SPLICE_PAGES | expand

Checks

Context Check Description
netdev/series_format fail Series longer than 15 patches (and no cover letter)
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 940 this patch: 940
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 7 of 7 maintainers
netdev/build_clang success Errors and warnings before: 956 this patch: 956
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 956 this patch: 956
netdev/checkpatch warning WARNING: line length of 93 exceeds 80 columns WARNING: line length of 95 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-03-06--21-00 (tests: 892)

Commit Message

David Howells March 6, 2024, 12:06 a.m. UTC
Clean up the DATA packet resending algorithm to retransmit packets as we
come across them whilst walking the transmission buffer rather than queuing
them for retransmission at the end.  This can be done as ACK parsing - and
thus the discarding of successful packets - is now done in the same thread
rather than separately in softirq context and a locked section is no longer
required.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org
---
 net/rxrpc/call_event.c | 79 ++++++++++++++++++++----------------------
 1 file changed, 38 insertions(+), 41 deletions(-)
diff mbox series

Patch

diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c
index 2a9f74eb7c46..6c5e3054209b 100644
--- a/net/rxrpc/call_event.c
+++ b/net/rxrpc/call_event.c
@@ -71,23 +71,18 @@  void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
 	struct rxrpc_skb_priv *sp;
 	struct rxrpc_txbuf *txb;
 	rxrpc_seq_t transmitted = call->tx_transmitted;
-	ktime_t now, max_age, oldest, ack_ts, delay;
-	bool unacked = false;
+	ktime_t next_resend = KTIME_MAX, rto = ns_to_ktime(call->peer->rto_us * NSEC_PER_USEC);
+	ktime_t resend_at = KTIME_MAX, now, delay;
+	bool unacked = false, did_send = false;
 	unsigned int i;
-	LIST_HEAD(retrans_queue);
 
 	_enter("{%d,%d}", call->acks_hard_ack, call->tx_top);
 
 	now = ktime_get_real();
-	max_age = ktime_sub_us(now, call->peer->rto_us);
-	oldest = now;
 
 	if (list_empty(&call->tx_buffer))
 		goto no_resend;
 
-	if (list_empty(&call->tx_buffer))
-		goto no_further_resend;
-
 	trace_rxrpc_resend(call, ack_skb);
 	txb = list_first_entry(&call->tx_buffer, struct rxrpc_txbuf, call_link);
 
@@ -115,19 +110,23 @@  void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
 			goto no_further_resend;
 
 		found_txb:
-			if (after(txb->serial, call->acks_highest_serial))
+			resend_at = ktime_add(txb->last_sent, rto);
+			if (after(txb->serial, call->acks_highest_serial)) {
+				if (ktime_after(resend_at, now) &&
+				    ktime_before(resend_at, next_resend))
+					next_resend = resend_at;
 				continue; /* Ack point not yet reached */
+			}
 
 			rxrpc_see_txbuf(txb, rxrpc_txbuf_see_unacked);
 
-			if (list_empty(&txb->tx_link)) {
-				list_add_tail(&txb->tx_link, &retrans_queue);
-				txb->flags |= RXRPC_TXBUF_RESENT;
-			}
-
 			trace_rxrpc_retransmit(call, txb->seq, txb->serial,
-					       ktime_to_ns(ktime_sub(txb->last_sent,
-								     max_age)));
+					       ktime_sub(resend_at, now));
+
+			txb->flags |= RXRPC_TXBUF_RESENT;
+			rxrpc_transmit_one(call, txb);
+			did_send = true;
+			now = ktime_get_real();
 
 			if (list_is_last(&txb->call_link, &call->tx_buffer))
 				goto no_further_resend;
@@ -144,6 +143,8 @@  void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
 		goto no_further_resend;
 
 	list_for_each_entry_from(txb, &call->tx_buffer, call_link) {
+		resend_at = ktime_add(txb->last_sent, rto);
+
 		if (before_eq(txb->seq, call->acks_prev_seq))
 			continue;
 		if (after(txb->seq, call->tx_transmitted))
@@ -153,25 +154,30 @@  void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
 		    before(txb->serial, ntohl(ack->serial)))
 			goto do_resend; /* Wasn't accounted for by a more recent ping. */
 
-		if (ktime_after(txb->last_sent, max_age)) {
-			if (ktime_before(txb->last_sent, oldest))
-				oldest = txb->last_sent;
+		if (ktime_after(resend_at, now)) {
+			if (ktime_before(resend_at, next_resend))
+				next_resend = resend_at;
 			continue;
 		}
 
 	do_resend:
 		unacked = true;
-		if (list_empty(&txb->tx_link)) {
-			list_add_tail(&txb->tx_link, &retrans_queue);
-			txb->flags |= RXRPC_TXBUF_RESENT;
-			rxrpc_inc_stat(call->rxnet, stat_tx_data_retrans);
-		}
+
+		txb->flags |= RXRPC_TXBUF_RESENT;
+		rxrpc_transmit_one(call, txb);
+		did_send = true;
+		rxrpc_inc_stat(call->rxnet, stat_tx_data_retrans);
+		now = ktime_get_real();
 	}
 
 no_further_resend:
 no_resend:
-	delay = rxrpc_get_rto_backoff(call->peer, !list_empty(&retrans_queue));
-	call->resend_at = ktime_add(oldest, delay);
+	if (resend_at < KTIME_MAX) {
+		delay = rxrpc_get_rto_backoff(call->peer, did_send);
+		resend_at = ktime_add(resend_at, delay);
+		trace_rxrpc_timer_set(call, resend_at - now, rxrpc_timer_trace_resend_reset);
+	}
+	call->resend_at = resend_at;
 
 	if (unacked)
 		rxrpc_congestion_timeout(call);
@@ -180,24 +186,15 @@  void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
 	 * that an ACK got lost somewhere.  Send a ping to find out instead of
 	 * retransmitting data.
 	 */
-	if (list_empty(&retrans_queue)) {
-		trace_rxrpc_timer_set(call, delay, rxrpc_timer_trace_resend_reset);
-		ack_ts = ktime_sub(now, call->acks_latest_ts);
-		if (ktime_to_us(ack_ts) < (call->peer->srtt_us >> 3))
-			goto out;
-		rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
-			       rxrpc_propose_ack_ping_for_0_retrans);
-		goto out;
-	}
+	if (!did_send) {
+		ktime_t next_ping = ktime_add_us(call->acks_latest_ts,
+						 call->peer->srtt_us >> 3);
 
-	/* Retransmit the queue */
-	while ((txb = list_first_entry_or_null(&retrans_queue,
-					       struct rxrpc_txbuf, tx_link))) {
-		list_del_init(&txb->tx_link);
-		rxrpc_transmit_one(call, txb);
+		if (ktime_sub(next_ping, now) <= 0)
+			rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
+				       rxrpc_propose_ack_ping_for_0_retrans);
 	}
 
-out:
 	_leave("");
 }