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Miller" , Eric Dumazet , Paolo Abeni , linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org, Marc Dionne , Jeffrey Altman , Simon Horman , stable@kernel.org Subject: [PATCH net v3 11/11] rxrpc: Fix to request an ack if window is limited Date: Thu, 26 Mar 2026 13:18:36 +0000 Message-ID: <20260326131838.634095-12-dhowells@redhat.com> In-Reply-To: <20260326131838.634095-1-dhowells@redhat.com> References: <20260326131838.634095-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 From: Marc Dionne 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: fe24a5494390 ("rxrpc: Send jumbo DATA packets") Signed-off-by: Marc Dionne Signed-off-by: David Howells cc: Jeffrey Altman cc: Eric Dumazet cc: "David S. Miller" cc: Jakub Kicinski cc: Paolo Abeni cc: Simon Horman cc: linux-afs@lists.infradead.org cc: netdev@vger.kernel.org cc: stable@kernel.org --- include/trace/events/rxrpc.h | 1 + net/rxrpc/ar-internal.h | 2 +- net/rxrpc/output.c | 2 ++ net/rxrpc/proc.c | 5 +++-- 4 files changed, 7 insertions(+), 3 deletions(-) diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h index 5edad6a624ad..792d0f944fc2 100644 --- a/include/trace/events/rxrpc.h +++ b/include/trace/events/rxrpc.h @@ -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 ") \ diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 36d6ca0d1089..96ecb83c9071 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -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; }; diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c index d70db367e358..870e59bf06af 100644 --- a/net/rxrpc/output.c +++ b/net/rxrpc/output.c @@ -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; diff --git a/net/rxrpc/proc.c b/net/rxrpc/proc.c index 59292f7f9205..7755fca5beb8 100644 --- a/net/rxrpc/proc.c +++ b/net/rxrpc/proc.c @@ -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]),