rxrpc: Request an ACK on impending Tx stall

Set the REQUEST-ACK flag on the DATA packet we're about to send if we're
about to stall transmission because the app layer isn't keeping up
supplying us with data to transmit.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://patch.msgid.link/20241204074710.990092-8-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h
index 62064f63d6eb8af1fb72237f2f89d208d592384f..d86b5f07d29260f95cdc996178b79174734805c5 100644 (file)
--- a/include/trace/events/rxrpc.h
+++ b/include/trace/events/rxrpc.h
@@ -452,6 +452,7 @@
 
 #define rxrpc_req_ack_traces \
        EM(rxrpc_reqack_ack_lost,               "ACK-LOST  ")   \
+       EM(rxrpc_reqack_app_stall,              "APP-STALL ")   \
        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 fcdfbc1d5aafa9b40a6c08b60e8294dbcafab1d1..d0fd37bdcfe9c8653192b8c7d9f07a55e938fb90 100644 (file)
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -110,7 +110,7 @@ struct rxrpc_net {
        atomic_t                stat_tx_acks[256];
        atomic_t                stat_rx_acks[256];
 
-       atomic_t                stat_why_req_ack[7];
+       atomic_t                stat_why_req_ack[8];
 
        atomic_t                stat_io_loop;
 };

diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index 50d5f2a02458a81febdaebc925d1035d48327c6b..b93a5d50be3e446408c9935a60b73442c1591340 100644 (file)
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -330,7 +330,7 @@ static void rxrpc_prepare_data_subpacket(struct rxrpc_call *call, struct rxrpc_t
        struct rxrpc_wire_header *whdr = txb->kvec[0].iov_base;
        enum rxrpc_req_ack_trace why;
        struct rxrpc_connection *conn = call->conn;
-       bool last;
+       bool last, more;
        u8 flags;
 
        _enter("%x,{%d}", txb->seq, txb->len);
@@ -345,6 +345,9 @@ static void rxrpc_prepare_data_subpacket(struct rxrpc_call *call, struct rxrpc_t
        flags = txb->flags & RXRPC_TXBUF_WIRE_FLAGS;
        last = txb->flags & RXRPC_LAST_PACKET;
 
+       more = (!list_is_last(&txb->call_link, &call->tx_buffer) ||
+               !list_empty(&call->tx_sendmsg));
+
        /* If our RTT cache needs working on, request an ACK.  Also request
         * ACKs if a DATA packet appears to have been lost.
         *
@@ -366,6 +369,8 @@ static void rxrpc_prepare_data_subpacket(struct rxrpc_call *call, struct rxrpc_t
                why = rxrpc_reqack_more_rtt;
        else if (ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000), ktime_get_real()))
                why = rxrpc_reqack_old_rtt;
+       else if (!last && !more)
+               why = rxrpc_reqack_app_stall;
        else
                goto dont_set_request_ack;
 

diff --git a/net/rxrpc/proc.c b/net/rxrpc/proc.c
index cdf32f0d8e0eab981ada897649040ec121741c47..ce4d48bdfbe9e954ff38815f957612d0456f9313 100644 (file)
--- a/net/rxrpc/proc.c
+++ b/net/rxrpc/proc.c
@@ -520,10 +520,11 @@ 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\n",
+                  "Why-Req-A: acklost=%u mrtt=%u ortt=%u stall=%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_old_rtt]),
+                  atomic_read(&rxnet->stat_why_req_ack[rxrpc_reqack_app_stall]));
        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]),