rxrpc: Cache the congestion window setting

Cache the congestion window setting that was determined during a call's
transmission phase when it finishes so that it can be used by the next call
to the same peer, thereby shortcutting the slow-start algorithm.

The value is stored in the rxrpc_peer struct and is accessed without
locking.  Each call takes the value that happens to be there when it starts
and just overwrites the value when it finishes.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index adbf379..69b9733 100644 (file)
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -300,6 +300,8 @@ struct rxrpc_peer {
        u64                     rtt_cache[RXRPC_RTT_CACHE_SIZE]; /* Determined RTT cache */
        u8                      rtt_cursor;     /* next entry at which to insert */
        u8                      rtt_usage;      /* amount of cache actually used */
+
+       u8                      cong_cwnd;      /* Congestion window size */
 };
 
 /*

diff --git a/net/rxrpc/call_accept.c b/net/rxrpc/call_accept.c
index 0d4d84e..dd30d74 100644 (file)
--- a/net/rxrpc/call_accept.c
+++ b/net/rxrpc/call_accept.c
@@ -310,6 +310,7 @@ static struct rxrpc_call *rxrpc_alloc_incoming_call(struct rxrpc_sock *rx,
        rxrpc_see_call(call);
        call->conn = conn;
        call->peer = rxrpc_get_peer(conn->params.peer);
+       call->cong_cwnd = call->peer->cong_cwnd;
        return call;
 }
 

diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index 423030f..d7809a0 100644 (file)
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -136,12 +136,7 @@ struct rxrpc_call *rxrpc_alloc_call(gfp_t gfp)
        call->tx_winsize = 16;
        call->rx_expect_next = 1;
 
-       if (RXRPC_TX_SMSS > 2190)
-               call->cong_cwnd = 2;
-       else if (RXRPC_TX_SMSS > 1095)
-               call->cong_cwnd = 3;
-       else
-               call->cong_cwnd = 4;
+       call->cong_cwnd = 2;
        call->cong_ssthresh = RXRPC_RXTX_BUFF_SIZE - 1;
        return call;
 

diff --git a/net/rxrpc/conn_client.c b/net/rxrpc/conn_client.c
index dd8bb91..eb21576 100644 (file)
--- a/net/rxrpc/conn_client.c
+++ b/net/rxrpc/conn_client.c
@@ -292,6 +292,12 @@ static int rxrpc_get_client_conn(struct rxrpc_call *call,
        if (!cp->peer)
                goto error;
 
+       call->cong_cwnd = cp->peer->cong_cwnd;
+       if (call->cong_cwnd >= call->cong_ssthresh)
+               call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
+       else
+               call->cong_mode = RXRPC_CALL_SLOW_START;
+
        /* If the connection is not meant to be exclusive, search the available
         * connections to see if the connection we want to use already exists.
         */

diff --git a/net/rxrpc/conn_object.c b/net/rxrpc/conn_object.c
index 5bb2551..929b50d 100644 (file)
--- a/net/rxrpc/conn_object.c
+++ b/net/rxrpc/conn_object.c
@@ -193,6 +193,8 @@ void rxrpc_disconnect_call(struct rxrpc_call *call)
 {
        struct rxrpc_connection *conn = call->conn;
 
+       call->peer->cong_cwnd = call->cong_cwnd;
+
        spin_lock_bh(&conn->params.peer->lock);
        hlist_del_init(&call->error_link);
        spin_unlock_bh(&conn->params.peer->lock);

diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c
index cfed3b2..5787f97 100644 (file)
--- a/net/rxrpc/peer_object.c
+++ b/net/rxrpc/peer_object.c
@@ -228,6 +228,13 @@ struct rxrpc_peer *rxrpc_alloc_peer(struct rxrpc_local *local, gfp_t gfp)
                seqlock_init(&peer->service_conn_lock);
                spin_lock_init(&peer->lock);
                peer->debug_id = atomic_inc_return(&rxrpc_debug_id);
+
+               if (RXRPC_TX_SMSS > 2190)
+                       peer->cong_cwnd = 2;
+               else if (RXRPC_TX_SMSS > 1095)
+                       peer->cong_cwnd = 3;
+               else
+                       peer->cong_cwnd = 4;
        }
 
        _leave(" = %p", peer);