LU-13501 lnet: Skip health and resends for single rail configs

If the sender of a message only has a single interface it doesn't
make sense to have LNet track the health of that interface, nor
should it attempt to resend a message when it encounters a local
error. There aren't any alternative interfaces to use for a resend.

Similarly, we needn't track health values of a peer's NIs if the peer
only has a single interface. Nor do we need to attempt to resend
a message to a peer with a single interface. There's an exception for
routers. We rely on NI health to determine route aliveness, so even
if a router only has a single interface we still need to track its
health.

We can use the ln_ping_target to get the count of local NIs, and the
lnet_peer struct already contains a count of the number of peer NIs.

HPE-bug-id: LUS-8826
Signed-off-by: Chris Horn <hornc@cray.com>
Change-Id: Id89159a5d07c1668c1cbdfa9050535380f68d1f6
Reviewed-on: https://review.whamcloud.com/38448
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>

diff --git a/lnet/lnet/lib-msg.c b/lnet/lnet/lib-msg.c
index d7e8436..8ab8194 100644 (file)
--- a/lnet/lnet/lib-msg.c
+++ b/lnet/lnet/lib-msg.c
@@ -780,6 +780,10 @@ lnet_health_check(struct lnet_msg *msg)
        struct lnet_peer_ni *lpni;
        struct lnet_ni *ni;
        bool lo = false;
+       bool attempt_local_resend;
+       bool attempt_remote_resend;
+       bool handle_local_health;
+       bool handle_remote_health;
 
        /* if we're shutting down no point in handling health. */
        if (the_lnet.ln_mt_state != LNET_MT_STATE_RUNNING)
@@ -808,9 +812,40 @@ lnet_health_check(struct lnet_msg *msg)
        if (msg->msg_tx_committed) {
                ni = msg->msg_txni;
                lpni = msg->msg_txpeer;
+               attempt_local_resend = attempt_remote_resend = true;
        } else {
                ni = msg->msg_rxni;
                lpni = msg->msg_rxpeer;
+               attempt_local_resend = attempt_remote_resend = false;
+       }
+
+       /* Don't further decrement the health value if a recovery message
+        * failed.
+        */
+       if (msg->msg_recovery)
+               handle_local_health = handle_remote_health = false;
+       else
+               handle_local_health = handle_remote_health = true;
+
+       /* For local failures, health/recovery/resends are not needed if I only
+        * have a single (non-lolnd) interface. NB: pb_nnis includes the lolnd
+        * interface, so a single-rail node would have pb_nnis == 2.
+        */
+       if (the_lnet.ln_ping_target->pb_nnis <= 2) {
+               handle_local_health = false;
+               attempt_local_resend = false;
+       }
+
+       /* For remote failures, health/recovery/resends are not needed if the
+        * peer only has a single interface. Special case for routers where we
+        * rely on health feature to manage route aliveness. NB: unlike pb_nnis
+        * above, lp_nnis does _not_ include the lolnd, so a single-rail node
+        * would have lp_nnis == 1.
+        */
+       if (lpni && lpni->lpni_peer_net->lpn_peer->lp_nnis <= 1) {
+               attempt_remote_resend = false;
+               if (!lnet_isrouter(lpni))
+                       handle_remote_health = false;
        }
 
        if (!lo)
@@ -877,45 +912,25 @@ lnet_health_check(struct lnet_msg *msg)
        case LNET_MSG_STATUS_LOCAL_ABORTED:
        case LNET_MSG_STATUS_LOCAL_NO_ROUTE:
        case LNET_MSG_STATUS_LOCAL_TIMEOUT:
-               /*
-                * don't further decrement the health value if the
-                * recovery message failed.
-                */
-               if (!msg->msg_recovery)
+               if (handle_local_health)
                        lnet_handle_local_failure(ni);
-               if (msg->msg_tx_committed)
-                       /* add to the re-send queue */
+               if (attempt_local_resend)
                        return lnet_attempt_msg_resend(msg);
                break;
-
-       /*
-        * These errors will not trigger a resend so simply
-        * finalize the message
-        */
        case LNET_MSG_STATUS_LOCAL_ERROR:
-               /*
-                * don't further decrement the health value if the
-                * recovery message failed.
-                */
-               if (!msg->msg_recovery)
+               if (handle_local_health)
                        lnet_handle_local_failure(ni);
                return -1;
-
-       /*
-        * TODO: since the remote dropped the message we can
-        * attempt a resend safely.
-        */
        case LNET_MSG_STATUS_REMOTE_DROPPED:
-               if (!msg->msg_recovery)
+               if (handle_remote_health)
                        lnet_handle_remote_failure(lpni);
-               if (msg->msg_tx_committed)
+               if (attempt_remote_resend)
                        return lnet_attempt_msg_resend(msg);
                break;
-
        case LNET_MSG_STATUS_REMOTE_ERROR:
        case LNET_MSG_STATUS_REMOTE_TIMEOUT:
        case LNET_MSG_STATUS_NETWORK_TIMEOUT:
-               if (!msg->msg_recovery)
+               if (handle_remote_health)
                        lnet_handle_remote_failure(lpni);
                return -1;
        default: