[PATCH 6.8 218/336] rxrpc: Only transmit one ACK per jumbo packet received

Greg Kroah-Hartman
2024-05-14T10:47:25Z

From: David Howells <dhowells@redhat.com>

[ Upstream commit 012b7206918dcc5a4dcf1432b3e643114c95957e ]

Only generate one ACK packet for all the subpackets in a jumbo packet. If
we would like to generate more than one ACK, we prioritise them base on
their reason code, in the order, highest first:

OutOfSeq > NoSpace > ExceedsWin > Duplicate > Requested > Delay > Idle

For the first four, we reference the lowest offending subpacket; for the
last three, the highest.

This reduces the number of ACKs we end up transmitting to one per UDP
packet transmitted to reduce network loading and packet parsing.

Fixes: 5d7edbc9231e ("rxrpc: Get rid of the Rx ring")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Reviewed-by: Jeffrey Altman <jaltman@auristor.com <mailto:jaltman@auristor.com>>
Link: https://lore.kernel.org/r/20240503150749.1001323-3-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/rxrpc/input.c | 46 +++++++++++++++++++++++++++++++++++-----------
1 file changed, 35 insertions(+), 11 deletions(-)

diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index f7304e06aadca..5dfda1ac51dda 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -9,6 +9,17 @@

#include "ar-internal.h"

+/* Override priority when generating ACKs for received DATA */
+static const u8 rxrpc_ack_priority[RXRPC_ACK__INVALID] = {
+ [RXRPC_ACK_IDLE] = 1,
+ [RXRPC_ACK_DELAY] = 2,
+ [RXRPC_ACK_REQUESTED] = 3,
+ [RXRPC_ACK_DUPLICATE] = 4,
+ [RXRPC_ACK_EXCEEDS_WINDOW] = 5,
+ [RXRPC_ACK_NOSPACE] = 6,
+ [RXRPC_ACK_OUT_OF_SEQUENCE] = 7,
+};
+
static void rxrpc_proto_abort(struct rxrpc_call *call, rxrpc_seq_t seq,
enum rxrpc_abort_reason why)
{
@@ -366,7 +377,7 @@ static void rxrpc_input_queue_data(struct rxrpc_call *call, struct sk_buff *skb,
* Process a DATA packet.
*/
static void rxrpc_input_data_one(struct rxrpc_call *call, struct sk_buff *skb,
- bool *_notify)
+ bool *_notify, rxrpc_serial_t *_ack_serial, int *_ack_reason)
{
struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
struct sk_buff *oos;
@@ -419,8 +430,6 @@ static void rxrpc_input_data_one(struct rxrpc_call *call, struct sk_buff *skb,
/* Send an immediate ACK if we fill in a hole */
else if (!skb_queue_empty(&call->rx_oos_queue))
ack_reason = RXRPC_ACK_DELAY;
- else
- call->ackr_nr_unacked++;

window++;
if (after(window, wtop)) {
@@ -498,12 +507,16 @@ static void rxrpc_input_data_one(struct rxrpc_call *call, struct sk_buff *skb,
}

send_ack:
- if (ack_reason >= 0)
- rxrpc_send_ACK(call, ack_reason, serial,
- rxrpc_propose_ack_input_data);
- else
- rxrpc_propose_delay_ACK(call, serial,
- rxrpc_propose_ack_input_data);
+ if (ack_reason >= 0) {
+ if (rxrpc_ack_priority[ack_reason] > rxrpc_ack_priority[*_ack_reason]) {
+ *_ack_serial = serial;
+ *_ack_reason = ack_reason;
+ } else if (rxrpc_ack_priority[ack_reason] == rxrpc_ack_priority[*_ack_reason] &&
+ ack_reason == RXRPC_ACK_REQUESTED) {
+ *_ack_serial = serial;
+ *_ack_reason = ack_reason;
+ }
+ }
}

/*
@@ -514,9 +527,11 @@ static bool rxrpc_input_split_jumbo(struct rxrpc_call *call, struct sk_buff *skb
struct rxrpc_jumbo_header jhdr;
struct rxrpc_skb_priv *sp = rxrpc_skb(skb), *jsp;
struct sk_buff *jskb;
+ rxrpc_serial_t ack_serial = 0;
unsigned int offset = sizeof(struct rxrpc_wire_header);
unsigned int len = skb->len - offset;
bool notify = false;
+ int ack_reason = 0;

while (sp->hdr.flags & RXRPC_JUMBO_PACKET) {
if (len < RXRPC_JUMBO_SUBPKTLEN)
@@ -536,7 +551,7 @@ static bool rxrpc_input_split_jumbo(struct rxrpc_call *call, struct sk_buff *skb
jsp = rxrpc_skb(jskb);
jsp->offset = offset;
jsp->len = RXRPC_JUMBO_DATALEN;
- rxrpc_input_data_one(call, jskb, &notify);
+ rxrpc_input_data_one(call, jskb, &notify, &ack_serial, &ack_reason);
rxrpc_free_skb(jskb, rxrpc_skb_put_jumbo_subpacket);

sp->hdr.flags = jhdr.flags;
@@ -549,7 +564,16 @@ static bool rxrpc_input_split_jumbo(struct rxrpc_call *call, struct sk_buff *skb

sp->offset = offset;
sp->len = len;
- rxrpc_input_data_one(call, skb, &notify);
+ rxrpc_input_data_one(call, skb, &notify, &ack_serial, &ack_reason);
+
+ if (ack_reason > 0) {
+ rxrpc_send_ACK(call, ack_reason, ack_serial,
+ rxrpc_propose_ack_input_data);
+ } else {
+ call->ackr_nr_unacked++;
+ rxrpc_propose_delay_ACK(call, sp->hdr.serial,
+ rxrpc_propose_ack_input_data);
+ }
if (notify) {
trace_rxrpc_notify_socket(call->debug_id, sp->hdr.serial);
rxrpc_notify_socket(call);
--
2.43.0