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rxrpc: Fix to request an ack if window is limited

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Peers may only send immediate acks for every 2 UDP packets received.
When sending a jumbogram, it is important to check that there is
sufficient window space to send another same sized jumbogram following
the current one, and request an ack if there isn't.  Failure to do so may
cause the call to stall waiting for an ack until the resend timer fires.

Where jumbograms are in use this causes a very significant drop in
performance.

Fixes: fe24a54943 ("rxrpc: Send jumbo DATA packets")
Signed-off-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
Link: https://patch.msgid.link/20260408121252.2249051-10-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Marc Dionne 2026-04-08 13:12:37 +01:00 committed by Jakub Kicinski
parent d666540d21
commit 0cd3e3f3f2
4 changed files with 7 additions and 3 deletions
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1
include/trace/events/rxrpc.h
View File

@ -521,6 +521,7 @@
#define rxrpc_req_ack_traces \
EM(rxrpc_reqack_ack_lost, "ACK-LOST ") \
EM(rxrpc_reqack_app_stall, "APP-STALL ") \
EM(rxrpc_reqack_jumbo_win, "JUMBO-WIN ") \
EM(rxrpc_reqack_more_rtt, "MORE-RTT ") \
EM(rxrpc_reqack_no_srv_last, "NO-SRVLAST") \
EM(rxrpc_reqack_old_rtt, "OLD-RTT ") \

2
net/rxrpc/ar-internal.h
View File

@ -117,7 +117,7 @@ struct rxrpc_net {
atomic_t stat_tx_jumbo[10];
atomic_t stat_rx_jumbo[10];
atomic_t stat_why_req_ack[8];
atomic_t stat_why_req_ack[9];
atomic_t stat_io_loop;
};

2
net/rxrpc/output.c
View File

@ -479,6 +479,8 @@ static size_t rxrpc_prepare_data_subpacket(struct rxrpc_call *call,
why = rxrpc_reqack_old_rtt;
else if (!last && !after(READ_ONCE(call->send_top), txb->seq))
why = rxrpc_reqack_app_stall;
else if (call->tx_winsize <= (2 * req->n) || call->cong_cwnd <= (2 * req->n))
why = rxrpc_reqack_jumbo_win;
else
goto dont_set_request_ack;

5
net/rxrpc/proc.c
View File

@ -518,11 +518,12 @@ int rxrpc_stats_show(struct seq_file *seq, void *v)
atomic_read(&rxnet->stat_rx_acks[RXRPC_ACK_IDLE]),
atomic_read(&rxnet->stat_rx_acks[0]));
seq_printf(seq,
"Why-Req-A: acklost=%u mrtt=%u ortt=%u stall=%u\n",
"Why-Req-A: acklost=%u mrtt=%u ortt=%u stall=%u jwin=%u\n",
atomic_read(&rxnet->stat_why_req_ack[rxrpc_reqack_ack_lost]),
atomic_read(&rxnet->stat_why_req_ack[rxrpc_reqack_more_rtt]),
atomic_read(&rxnet->stat_why_req_ack[rxrpc_reqack_old_rtt]),
atomic_read(&rxnet->stat_why_req_ack[rxrpc_reqack_app_stall]));
atomic_read(&rxnet->stat_why_req_ack[rxrpc_reqack_app_stall]),
atomic_read(&rxnet->stat_why_req_ack[rxrpc_reqack_jumbo_win]));
seq_printf(seq,
"Why-Req-A: nolast=%u retx=%u slows=%u smtxw=%u\n",
atomic_read(&rxnet->stat_why_req_ack[rxrpc_reqack_no_srv_last]),