[ovs-dev] [PATCH v3 4/6] dpif-netdev: Change rxq_scheduling to use rxq processing cycles.

[Kevin Traynor]

Previously rxqs were assigned to pmds by round robin in
port/queue order.

Now that we have the processing cycles used for existing rxqs,
use that information to try and produced a better balanced
distribution of rxqs across pmds. i.e. given multiple pmds, the
rxqs which have consumed the largest amount of processing cycles
will be placed on different pmds.

The rxqs are sorted by their processing cycles and assigned (in
sorted order) round robin across pmds.

Signed-off-by: Kevin Traynor <ktraynor at redhat.com>
---
 Documentation/howto/dpdk.rst |  7 +++++
 lib/dpif-netdev.c            | 73 +++++++++++++++++++++++++++++++++++---------
 2 files changed, 66 insertions(+), 14 deletions(-)

diff --git a/Documentation/howto/dpdk.rst b/Documentation/howto/dpdk.rst
index af01d3e..a969285 100644
--- a/Documentation/howto/dpdk.rst
+++ b/Documentation/howto/dpdk.rst
@@ -119,4 +119,11 @@ After that PMD threads on cores where RX queues was pinned will become
   thread.
 
+If pmd-rxq-affinity is not set for rxqs, they will be assigned to pmds (cores)
+automatically. The processing cycles that have been required for each rxq
+will be used where known to assign rxqs with the highest consumption of
+processing cycles to different pmds.
+
+Rxq to pmds assignment takes place whenever there are configuration changes.
+
 QoS
 ---
diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 25a521a..a05e586 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -3295,8 +3295,29 @@ rr_numa_list_destroy(struct rr_numa_list *rr)
 }
 
+/* Sort Rx Queues by the processing cycles they are consuming. */
+static int
+rxq_cycle_sort(const void *a, const void *b)
+{
+    struct dp_netdev_rxq * qa;
+    struct dp_netdev_rxq * qb;
+
+    qa = *(struct dp_netdev_rxq **) a;
+    qb = *(struct dp_netdev_rxq **) b;
+
+    if (dp_netdev_rxq_get_cycles(qa, RXQ_CYCLES_PROC_LAST) >=
+            dp_netdev_rxq_get_cycles(qb, RXQ_CYCLES_PROC_LAST)) {
+        return -1;
+    }
+
+    return 1;
+}
+
 /* Assign pmds to queues.  If 'pinned' is true, assign pmds to pinned
  * queues and marks the pmds as isolated.  Otherwise, assign non isolated
  * pmds to unpinned queues.
  *
+ * If 'pinned' is false queues will be sorted by processing cycles they are
+ * consuming and then assigned to pmds in round robin order.
+ *
  * The function doesn't touch the pmd threads, it just stores the assignment
  * in the 'pmd' member of each rxq. */
@@ -3306,18 +3327,14 @@ rxq_scheduling(struct dp_netdev *dp, bool pinned) OVS_REQUIRES(dp->port_mutex)
     struct dp_netdev_port *port;
     struct rr_numa_list rr;
-
-    rr_numa_list_populate(dp, &rr);
+    struct dp_netdev_rxq ** rxqs = NULL;
+    int i, n_rxqs = 0;
+    struct rr_numa *numa = NULL;
+    int numa_id;
 
     HMAP_FOR_EACH (port, node, &dp->ports) {
-        struct rr_numa *numa;
-        int numa_id;
-
         if (!netdev_is_pmd(port->netdev)) {
             continue;
         }
 
-        numa_id = netdev_get_numa_id(port->netdev);
-        numa = rr_numa_list_lookup(&rr, numa_id);
-
         for (int qid = 0; qid < port->n_rxq; qid++) {
             struct dp_netdev_rxq *q = &port->rxqs[qid];
@@ -3337,17 +3354,45 @@ rxq_scheduling(struct dp_netdev *dp, bool pinned) OVS_REQUIRES(dp->port_mutex)
                 }
             } else if (!pinned && q->core_id == OVS_CORE_UNSPEC) {
-                if (!numa) {
-                    VLOG_WARN("There's no available (non isolated) pmd thread "
-                              "on numa node %d. Queue %d on port \'%s\' will "
-                              "not be polled.",
-                              numa_id, qid, netdev_get_name(port->netdev));
+                if (n_rxqs == 0) {
+                    rxqs = xmalloc(sizeof *rxqs);
                 } else {
-                    q->pmd = rr_numa_get_pmd(numa);
+                    rxqs = xrealloc(rxqs, sizeof *rxqs * (n_rxqs + 1));
                 }
+                /* Store the queue. */
+                rxqs[n_rxqs++] = q;
             }
         }
     }
 
+    if (n_rxqs > 1) {
+        /* Sort the queues in order of the processing cycles
+         * they consumed during their last pmd interval. */
+        qsort(rxqs, n_rxqs, sizeof *rxqs, rxq_cycle_sort);
+    }
+
+    rr_numa_list_populate(dp, &rr);
+    /* Assign the sorted queues to pmds in round robin. */
+    for (i = 0; i < n_rxqs; i++) {
+        numa_id = netdev_get_numa_id(rxqs[i]->port->netdev);
+        numa = rr_numa_list_lookup(&rr, numa_id);
+        if (!numa) {
+            VLOG_WARN("There's no available (non isolated) pmd thread "
+                      "on numa node %d. Queue %d on port \'%s\' will "
+                      "not be polled.",
+                      numa_id, netdev_rxq_get_queue_id(rxqs[i]->rx),
+                      netdev_get_name(rxqs[i]->port->netdev));
+            continue;
+        }
+        rxqs[i]->pmd = rr_numa_get_pmd(numa);
+        VLOG_INFO("Core %d on numa node %d assigned port \'%s\' "
+                  "rx queue %d (measured processing cycles %"PRIu64").",
+                  rxqs[i]->pmd->core_id, numa_id,
+                  netdev_rxq_get_name(rxqs[i]->rx),
+                  netdev_rxq_get_queue_id(rxqs[i]->rx),
+                  dp_netdev_rxq_get_cycles(rxqs[i], RXQ_CYCLES_PROC_LAST));
+    }
+
     rr_numa_list_destroy(&rr);
+    free(rxqs);
 }
 
-- 
1.8.3.1