[ovs-dev,v3,3/4] revalidator: Rebalance offloaded flows based on the pps rate

Message ID 20180710062938.18939-4-sriharsha.basavapatna@broadcom.com
State Superseded
Headers show
Series
  • Support dynamic rebalancing of offloaded flows
Related show

Commit Message

Sriharsha Basavapatna via dev July 10, 2018, 6:29 a.m.
This is the third patch in the patch-set to support dynamic rebalancing
of offloaded flows.

The dynamic rebalancing functionality is implemented in this patch. The
ukeys that are not scheduled for deletion are obtained and passed as input
to the rebalancing routine. The rebalancing is done in the context of
revalidation leader thread, after all other revalidator threads are
done with gathering rebalancing data for flows.

For each netdev that is in OOR state, a list of flows - both offloaded
and non-offloaded (pending) - is obtained using the ukeys. For each netdev
that is in OOR state, the flows are grouped and sorted into offloaded and
pending flows.  The offloaded flows are sorted in descending order of
pps-rate, while pending flows are sorted in ascending order of pps-rate.

The rebalancing is done in two phases. In the first phase, we try to
offload all pending flows and if that succeeds, the OOR state on the device
is cleared. If some (or none) of the pending flows could not be offloaded,
then we start replacing an offloaded flow that has a lower pps-rate than
a pending flow, until there are no more pending flows with a higher rate
than an offloaded flow. The flows that are replaced from the device are
added into kernel datapath.

Signed-off-by: Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>
Co-authored-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>
Signed-off-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>
Reviewed-by: Sathya Perla <sathya.perla@broadcom.com>
---
 lib/dpif-netdev.c             |   3 +-
 lib/dpif-netlink.c            |  14 +-
 lib/dpif-provider.h           |   7 +-
 lib/dpif.c                    |  20 +-
 lib/dpif.h                    |  20 +-
 lib/netdev-provider.h         |   3 +-
 ofproto/ofproto-dpif-upcall.c | 418 +++++++++++++++++++++++++++++++++-
 7 files changed, 464 insertions(+), 21 deletions(-)

Patch

diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 9390fff68..ad5aac62b 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -3052,7 +3052,8 @@  dpif_netdev_execute(struct dpif *dpif, struct dpif_execute *execute)
 }
 
 static void
-dpif_netdev_operate(struct dpif *dpif, struct dpif_op **ops, size_t n_ops)
+dpif_netdev_operate(struct dpif *dpif, struct dpif_op **ops, size_t n_ops,
+                    enum dpif_op_skip_type skip_flag OVS_UNUSED)
 {
     size_t i;
 
diff --git a/lib/dpif-netlink.c b/lib/dpif-netlink.c
index 5a6d53ad5..3c4b9b69f 100644
--- a/lib/dpif-netlink.c
+++ b/lib/dpif-netlink.c
@@ -2276,7 +2276,8 @@  dpif_netlink_operate_chunks(struct dpif_netlink *dpif, struct dpif_op **ops,
 }
 
 static void
-dpif_netlink_operate(struct dpif *dpif_, struct dpif_op **ops, size_t n_ops)
+dpif_netlink_operate(struct dpif *dpif_, struct dpif_op **ops, size_t n_ops,
+                     enum dpif_op_skip_type skip_flag)
 {
     struct dpif_netlink *dpif = dpif_netlink_cast(dpif_);
     struct dpif_op *new_ops[OPERATE_MAX_OPS];
@@ -2284,7 +2285,7 @@  dpif_netlink_operate(struct dpif *dpif_, struct dpif_op **ops, size_t n_ops)
     int i = 0;
     int err = 0;
 
-    if (netdev_is_flow_api_enabled()) {
+    if (skip_flag != DPIF_OP_SKIP_OFFLOAD && netdev_is_flow_api_enabled()) {
         while (n_ops > 0) {
             count = 0;
 
@@ -2293,6 +2294,10 @@  dpif_netlink_operate(struct dpif *dpif_, struct dpif_op **ops, size_t n_ops)
 
                 err = try_send_to_netdev(dpif, op);
                 if (err && err != EEXIST) {
+                    if (skip_flag == DPIF_OP_SKIP_DP) {
+                        op->error = err;
+                        return;
+                    }
                     new_ops[count++] = op;
                 } else {
                     op->error = err;
@@ -2303,8 +2308,11 @@  dpif_netlink_operate(struct dpif *dpif_, struct dpif_op **ops, size_t n_ops)
 
             dpif_netlink_operate_chunks(dpif, new_ops, count);
         }
-    } else {
+    } else if (skip_flag != DPIF_OP_SKIP_DP) {
         dpif_netlink_operate_chunks(dpif, ops, n_ops);
+    } else {
+        VLOG_ERR("%s: Invalid skip_flag: %d while flow api is disabled\n",
+                 __func__, skip_flag);
     }
 }
 
diff --git a/lib/dpif-provider.h b/lib/dpif-provider.h
index cc6571b28..2bbfcf7f6 100644
--- a/lib/dpif-provider.h
+++ b/lib/dpif-provider.h
@@ -296,12 +296,13 @@  struct dpif_class {
 
     int (*flow_dump_next)(struct dpif_flow_dump_thread *thread,
                           struct dpif_flow *flows, int max_flows);
-
     /* Executes each of the 'n_ops' operations in 'ops' on 'dpif', in the order
      * in which they are specified, placing each operation's results in the
      * "output" members documented in comments and the 'error' member of each
-     * dpif_op. */
-    void (*operate)(struct dpif *dpif, struct dpif_op **ops, size_t n_ops);
+     * dpif_op. The skip_flag argument tells the provider if 'ops' should be
+     * offloaded to a netdev or to the kernel datapath or to both. */
+    void (*operate)(struct dpif *dpif, struct dpif_op **ops, size_t n_ops,
+                    enum dpif_op_skip_type skip_flag);
 
     /* Enables or disables receiving packets with dpif_recv() for 'dpif'.
      * Turning packet receive off and then back on is allowed to change Netlink
diff --git a/lib/dpif.c b/lib/dpif.c
index f6a7f6a72..d3eec1124 100644
--- a/lib/dpif.c
+++ b/lib/dpif.c
@@ -49,6 +49,7 @@ 
 #include "valgrind.h"
 #include "openvswitch/ofp-errors.h"
 #include "openvswitch/vlog.h"
+#include "lib/netdev-provider.h"
 
 VLOG_DEFINE_THIS_MODULE(dpif);
 
@@ -1010,7 +1011,7 @@  dpif_flow_get(struct dpif *dpif,
     op.flow_get.flow->key_len = key_len;
 
     opp = &op;
-    dpif_operate(dpif, &opp, 1);
+    dpif_operate(dpif, &opp, 1, DPIF_OP_SKIP_NONE);
 
     return op.error;
 }
@@ -1040,7 +1041,7 @@  dpif_flow_put(struct dpif *dpif, enum dpif_flow_put_flags flags,
     op.flow_put.stats = stats;
 
     opp = &op;
-    dpif_operate(dpif, &opp, 1);
+    dpif_operate(dpif, &opp, 1, DPIF_OP_SKIP_NONE);
 
     return op.error;
 }
@@ -1063,7 +1064,7 @@  dpif_flow_del(struct dpif *dpif,
     op.flow_del.terse = false;
 
     opp = &op;
-    dpif_operate(dpif, &opp, 1);
+    dpif_operate(dpif, &opp, 1, DPIF_OP_SKIP_NONE);
 
     return op.error;
 }
@@ -1320,7 +1321,7 @@  dpif_execute(struct dpif *dpif, struct dpif_execute *execute)
         op.execute = *execute;
 
         opp = &op;
-        dpif_operate(dpif, &opp, 1);
+        dpif_operate(dpif, &opp, 1, DPIF_OP_SKIP_NONE);
 
         return op.error;
     } else {
@@ -1331,9 +1332,12 @@  dpif_execute(struct dpif *dpif, struct dpif_execute *execute)
 /* Executes each of the 'n_ops' operations in 'ops' on 'dpif', in the order in
  * which they are specified.  Places each operation's results in the "output"
  * members documented in comments, and 0 in the 'error' member on success or a
- * positive errno on failure. */
+ * positive errno on failure. The skip_flag argument tells the provider if
+ * 'ops' should be offloaded to a netdev or to the kernel datapath or to both.
+ */
 void
-dpif_operate(struct dpif *dpif, struct dpif_op **ops, size_t n_ops)
+dpif_operate(struct dpif *dpif, struct dpif_op **ops, size_t n_ops,
+             enum dpif_op_skip_type skip_flag)
 {
     while (n_ops > 0) {
         size_t chunk;
@@ -1355,7 +1359,7 @@  dpif_operate(struct dpif *dpif, struct dpif_op **ops, size_t n_ops)
              * handle itself, without help. */
             size_t i;
 
-            dpif->dpif_class->operate(dpif, ops, chunk);
+            dpif->dpif_class->operate(dpif, ops, chunk, skip_flag);
 
             for (i = 0; i < chunk; i++) {
                 struct dpif_op *op = ops[i];
@@ -1652,7 +1656,7 @@  dpif_queue_to_priority(const struct dpif *dpif, uint32_t queue_id,
     log_operation(dpif, "queue_to_priority", error);
     return error;
 }
-
+
 void
 dpif_init(struct dpif *dpif, const struct dpif_class *dpif_class,
           const char *name,
diff --git a/lib/dpif.h b/lib/dpif.h
index 33d2d0bec..cc3ba343b 100644
--- a/lib/dpif.h
+++ b/lib/dpif.h
@@ -614,6 +614,23 @@  enum dpif_op_type {
     DPIF_OP_FLOW_GET,
 };
 
+/* skip_flag argument types to (*operate) interface */
+enum dpif_op_skip_type {
+    DPIF_OP_SKIP_NONE = 1,	/* If Offload enabled:
+                                 *                    Offload first; if it
+                                 *                    fails, go to datapath.
+                                 * If Offload disabled: Go to datapath.
+                                 */
+
+    DPIF_OP_SKIP_OFFLOAD,	/* Go to datapath only; do not offload even if
+                                 * Offload enabled
+                                 */
+
+    DPIF_OP_SKIP_DP		/* Do not go to datapath, even if Offload
+                                 * enabled and fail to offload.
+                                 */
+};
+
 /* Add or modify a flow.
  *
  * The flow is specified by the Netlink attributes with types OVS_KEY_ATTR_* in
@@ -768,7 +785,8 @@  struct dpif_op {
     };
 };
 
-void dpif_operate(struct dpif *, struct dpif_op **ops, size_t n_ops);
+void dpif_operate(struct dpif *, struct dpif_op **ops, size_t n_ops,
+                  enum dpif_op_skip_type skip_flag);
 
 /* Upcalls. */
 
diff --git a/lib/netdev-provider.h b/lib/netdev-provider.h
index 62e05619e..5c919f4a1 100644
--- a/lib/netdev-provider.h
+++ b/lib/netdev-provider.h
@@ -38,6 +38,8 @@  struct netdev_tnl_build_header_params;
 /* Offload-capable (HW) netdev information */
 struct netdev_hw_info {
     bool oor;		/* Out of Offload Resources ? */
+    int offload_count;
+    int pending_count;
 };
 
 /* A network device (e.g. an Ethernet device).
@@ -85,7 +87,6 @@  struct netdev {
     int n_rxq;
     struct shash_node *node;            /* Pointer to element in global map. */
     struct ovs_list saved_flags_list; /* Contains "struct netdev_saved_flags". */
-
     struct netdev_hw_info hw_info;	/* offload-capable netdev info */
 };
 
diff --git a/ofproto/ofproto-dpif-upcall.c b/ofproto/ofproto-dpif-upcall.c
index 355be9f39..cf1524615 100644
--- a/ofproto/ofproto-dpif-upcall.c
+++ b/ofproto/ofproto-dpif-upcall.c
@@ -22,6 +22,7 @@ 
 #include "connmgr.h"
 #include "coverage.h"
 #include "cmap.h"
+#include "lib/dpif-provider.h"
 #include "dpif.h"
 #include "openvswitch/dynamic-string.h"
 #include "fail-open.h"
@@ -42,7 +43,6 @@ 
 #include "tunnel.h"
 #include "unixctl.h"
 #include "openvswitch/vlog.h"
-#include "lib/dpif-provider.h"
 #include "lib/netdev-provider.h"
 
 #define MAX_QUEUE_LENGTH 512
@@ -399,6 +399,18 @@  static int upcall_receive(struct upcall *, const struct dpif_backer *,
                           const ovs_u128 *ufid, const unsigned pmd_id);
 static void upcall_uninit(struct upcall *);
 
+static void udpif_flow_rebalance_prepare(struct udpif *udpif,
+                                         struct udpif_key ***
+                                         active_flows,
+                                         int *num_active_flows);
+static void udpif_flow_rebalance(struct udpif *udpif,
+                                 struct udpif_key **active_flows,
+                                 int num_active_flows);
+static int udpif_flow_program(struct udpif *udpif, struct udpif_key *ukey,
+                              enum dpif_op_skip_type skip_flag);
+static int udpif_flow_unprogram(struct udpif *udpif, struct udpif_key *ukey,
+                                enum dpif_op_skip_type skip_flag);
+
 static upcall_callback upcall_cb;
 static dp_purge_callback dp_purge_cb;
 
@@ -862,6 +874,25 @@  free_dupcall:
     return n_upcalls;
 }
 
+static void
+udpif_run_flow_rebalance(struct udpif *udpif)
+{
+    struct udpif_key **active_flows = NULL;
+    static long long int time = 0;
+    static long long int now = 0;
+    int num_active_flows;
+
+    /* Don't rebalance if OFFL_REBAL_INTVL_MSEC have not elapsed */
+    now = time_msec();
+    if (now < time + OFFL_REBAL_INTVL_MSEC) {
+        return;
+    }
+    time = now;
+
+    udpif_flow_rebalance_prepare(udpif, &active_flows, &num_active_flows);
+    udpif_flow_rebalance(udpif, active_flows, num_active_flows);
+}
+
 static void *
 udpif_revalidator(void *arg)
 {
@@ -936,6 +967,7 @@  udpif_revalidator(void *arg)
 
             dpif_flow_dump_destroy(udpif->dump);
             seq_change(udpif->dump_seq);
+            udpif_run_flow_rebalance(udpif);
 
             duration = MAX(time_msec() - start_time, 1);
             udpif->dump_duration = duration;
@@ -1582,7 +1614,7 @@  handle_upcalls(struct udpif *udpif, struct upcall *upcalls,
     for (i = 0; i < n_ops; i++) {
         opsp[n_opsp++] = &ops[i].dop;
     }
-    dpif_operate(udpif->dpif, opsp, n_opsp);
+    dpif_operate(udpif->dpif, opsp, n_opsp, DPIF_OP_SKIP_NONE);
     for (i = 0; i < n_ops; i++) {
         struct udpif_key *ukey = ops[i].ukey;
 
@@ -1674,7 +1706,7 @@  ukey_create__(const struct nlattr *key, size_t key_len,
     ukey->state = UKEY_CREATED;
     ukey->state_thread = ovsthread_id_self();
     ukey->state_where = OVS_SOURCE_LOCATOR;
-    ukey->created = time_msec();
+    ukey->created = ukey->flow_time = time_msec();
     memset(&ukey->stats, 0, sizeof ukey->stats);
     ukey->stats.used = used;
     ukey->xcache = NULL;
@@ -2333,7 +2365,7 @@  push_dp_ops(struct udpif *udpif, struct ukey_op *ops, size_t n_ops)
     for (i = 0; i < n_ops; i++) {
         opsp[i] = &ops[i].dop;
     }
-    dpif_operate(udpif->dpif, opsp, n_ops);
+    dpif_operate(udpif->dpif, opsp, n_ops, DPIF_OP_SKIP_NONE);
 
     for (i = 0; i < n_ops; i++) {
         struct ukey_op *op = &ops[i];
@@ -2564,6 +2596,16 @@  udpif_flow_time_delta(struct udpif *udpif, struct udpif_key *ukey)
     return (udpif->dpif->current_ms - ukey->flow_time) / 1000;
 }
 
+/*
+ * Save backlog packet count while switching modes
+ * between offloaded and kernel datapaths.
+ */
+static void
+udpif_set_ukey_backlog_packets(struct udpif_key *ukey)
+{
+    ukey->flow_backlog_packets = ukey->flow_packets;
+}
+
 /* Gather pps-rate for the given dpif_flow and save it in its ukey */
 static void
 udpif_update_flow_pps(struct udpif *udpif, struct udpif_key *ukey,
@@ -2641,6 +2683,7 @@  revalidate(struct revalidator *revalidator)
         kill_them_all = n_dp_flows > flow_limit * 2;
         max_idle = n_dp_flows > flow_limit ? 100 : ofproto_max_idle;
 
+        udpif->dpif->current_ms = time_msec();
         for (f = flows; f < &flows[n_dumped]; f++) {
             long long int used = f->stats.used;
             struct recirc_refs recircs = RECIRC_REFS_EMPTY_INITIALIZER;
@@ -3016,3 +3059,370 @@  upcall_unixctl_purge(struct unixctl_conn *conn, int argc OVS_UNUSED,
     }
     unixctl_command_reply(conn, "");
 }
+
+/*
+ * Walk umaps and build an array of pointers to ukeys. That
+ * serves as the input to udpif_flow_rebalance() routine.
+ */
+static void
+udpif_flow_rebalance_prepare(struct udpif *udpif, struct udpif_key
+                             ***active_flows, int *num_active_flows)
+{
+    struct udpif_key **f = NULL;
+    size_t n = 0;
+    size_t i;
+    size_t j;
+
+    if (!active_flows || !num_active_flows) {
+        return;
+    }
+
+    for (i = 0; i < N_UMAPS; i++) {
+        struct umap *umap = &udpif->ukeys[i];
+        n += cmap_count(&umap->cmap);
+    }
+
+    f = xzalloc(n * sizeof(*f));
+
+    for (i = 0, j = 0; i < N_UMAPS; i++) {
+        struct udpif_key *ukey;
+        struct umap *umap = &udpif->ukeys[i];
+
+        CMAP_FOR_EACH (ukey, cmap_node, &umap->cmap) {
+                f[j++] = ukey;
+                if (j >= n) {
+                   goto done;
+                }
+        }
+    }
+
+done:
+    *active_flows = f;
+    *num_active_flows = n;
+}
+
+/* Flows are sorted in the following order:
+ * netdev name, flow state (offloaded/kernel path), flow_pps_rate.
+ */
+static int
+flow_compare_rebalance(const void *elem1, const void *elem2)
+{
+    const struct udpif_key *f1 =
+                *(struct udpif_key **)elem1;
+    const struct udpif_key *f2 =
+                *(struct udpif_key **)elem2;
+    struct netdev *netdev1;
+    struct netdev *netdev2;
+    int rv;
+
+    netdev1 = f1->tunnel_netdev ? f1->tunnel_netdev : f1->in_netdev;
+    netdev2 = f2->tunnel_netdev ? f2->tunnel_netdev : f2->in_netdev;
+
+    rv = strcmp(netdev1->name, netdev2->name);
+    if (rv) {
+        return (rv);
+    }
+
+    if (f1->offloaded != f2->offloaded) {
+        return (f2->offloaded - f1->offloaded);
+    }
+
+    float diff = (f1->offloaded == true) ?
+        f1->flow_pps_rate - f2->flow_pps_rate :
+        f2->flow_pps_rate - f1->flow_pps_rate;
+
+    return (diff < 0) ? -1 : 1;
+}
+
+/* Insert flows from pending array during rebalancing */
+static int
+rebalance_insert_pending(struct udpif *udpif, struct udpif_key **pending_flows,
+                         int pending_count, int insert_count,
+                         float rate_threshold)
+{
+    int i, err = 0;
+    struct udpif_key *flow;
+    int count = 0;
+
+    for (i = 0; i < pending_count; i++) {
+        flow = pending_flows[i];
+
+        /* Stop offloading pending flows if the insert count is
+         * reached and the flow rate is less than the threshold
+         */
+        if ((count >= insert_count) &&
+            (flow->flow_pps_rate < rate_threshold)) {
+                break;
+        }
+
+        /* Offload the flow to netdev */
+        err = udpif_flow_program(udpif, flow, DPIF_OP_SKIP_DP);
+
+        if (err == ENOSPC) {
+            /* Stop if we are out of resources */
+            break;
+        }
+
+        if (err) {
+            continue;
+        }
+
+        /* Offload succeeded; delete it from the kernel datapath */
+        udpif_flow_unprogram(udpif, flow, DPIF_OP_SKIP_OFFLOAD);
+
+        /* Change the state of the flow, adjust dpif counters */
+        flow->offloaded = true;
+
+        udpif_set_ukey_backlog_packets(flow);
+        count++;
+    }
+
+    return count;
+}
+
+/* Remove flows from offloaded array during rebalancing */
+static void
+rebalance_remove_offloaded(struct udpif *udpif,
+                           struct udpif_key **offloaded_flows,
+                           int offload_count)
+{
+    int i;
+    struct udpif_key *flow;
+
+    for (i = 0; i < offload_count; i++) {
+        flow = offloaded_flows[i];
+
+        /* Remove offloaded flow from netdev */
+        udpif_flow_unprogram(udpif, flow, DPIF_OP_SKIP_DP);
+
+        /* Install the flow into kernel path */
+        udpif_flow_program(udpif, flow, DPIF_OP_SKIP_OFFLOAD);
+        flow->offloaded = false;
+
+        udpif_set_ukey_backlog_packets(flow);
+    }
+}
+
+/*
+ * Rebalance offloaded flows on a netdev that's in OOR state.
+ *
+ * The rebalancing is done in two phases. In the first phase, we check if
+ * the pending flows can be offloaded (if some resources became available
+ * in the meantime) by trying to offload each pending flow. If all pending
+ * flows get successfully offloaded, the OOR state is cleared on the netdev
+ * and there's nothing to rebalance.
+ *
+ * If some of the pending flows could not be offloaded, i.e, we still see
+ * the OOR error, then we move to the second phase of rebalancing. In this
+ * phase, the rebalancer compares pps-rate of an offloaded flow with the
+ * least pps-rate with that of a pending flow with the highest pps-rate from
+ * their respective sorted arrays. If pps-rate of the offloaded flow is less
+ * than the pps-rate of the pending flow, then it deletes the offloaded flow
+ * from the HW/netdev and adds it to kernel datapath and then offloads pending
+ * to HW/netdev. This process is repeated for every pair of offloaded and
+ * pending flows in the ordered list. The process stops when we encounter an
+ * offloaded flow that has a higher pps-rate than the corresponding pending
+ * flow. The entire rebalancing process is repeated in the next iteration.
+ */
+static bool
+rebalance_device(struct udpif *udpif, struct udpif_key **offloaded_flows,
+                 int offload_count, struct udpif_key **pending_flows,
+                 int pending_count)
+{
+
+    /* Phase 1 */
+    int num_inserted = rebalance_insert_pending(udpif, pending_flows,
+                                                pending_count, pending_count,
+                                                0.0);
+    if (num_inserted) {
+        VLOG_DBG("Offload rebalance: Phase1: inserted %d pending flows\n",
+                  num_inserted);
+    }
+
+    /* Adjust pending array */
+    pending_flows = &pending_flows[num_inserted];
+    pending_count -= num_inserted;
+
+    if (!pending_count) {
+    /*
+     * Successfully offloaded all pending flows. The device
+     * is no longer in OOR state; done rebalancing this device.
+     */
+        return false;
+    }
+
+    /*
+     * Phase 2; determine how many offloaded flows to churn.
+     */
+    int churn_count = 0;
+    while ((churn_count < offload_count) &&
+           (churn_count < pending_count)) {
+        if (pending_flows[churn_count]->flow_pps_rate <=
+            offloaded_flows[churn_count]->flow_pps_rate)
+                break;
+        churn_count++;
+    }
+
+    if (churn_count) {
+        VLOG_DBG("Offload rebalance: Phase2: removed %d offloaded flows\n",
+                  churn_count);
+    }
+
+    /* Bail early if nothing to churn */
+    if (!churn_count) {
+        return true;
+    }
+
+    /* Remove offloaded flows */
+    rebalance_remove_offloaded(udpif, offloaded_flows, churn_count);
+
+    /* Adjust offloaded array */
+    offloaded_flows = &offloaded_flows[churn_count];
+    offload_count -= churn_count;
+
+    /* Replace offloaded flows with pending flows */
+    num_inserted = rebalance_insert_pending(udpif, pending_flows,
+                                            pending_count, churn_count,
+                                            offload_count ?
+                                            offloaded_flows[0]->flow_pps_rate :
+                                            0.0);
+    if (num_inserted) {
+        VLOG_DBG("Offload rebalance: Phase2: inserted %d pending flows\n",
+                  num_inserted);
+    }
+
+    return true;
+}
+
+/*
+ * Given all ukeys that are active in the datapath, rebalance
+ * offloaded flows on HW netdevs that are in OOR state.
+ */
+static void
+udpif_flow_rebalance(struct udpif *udpif,
+                     struct udpif_key **active_flows,
+                     int num_active_flows)
+{
+    struct udpif_key **sort_flows = NULL;
+    int total_offload_count = 0;
+    int total_pending_count = 0;
+    int total_flow_count = 0;
+    int oor_netdev_count = 0;
+    struct udpif_key *ukey;
+    struct netdev *netdev;
+    int offload_index = 0;
+    int pending_index;
+    bool oor;
+    int i;
+
+    if (!num_active_flows) {
+       return;
+    }
+
+    sort_flows = xzalloc(sizeof(*sort_flows) * num_active_flows);
+
+    /* Populate sort_flows[] initially with flows that
+     * have an 'OOR' device as their input or output port
+     */
+    for (i = 0; i < num_active_flows; i++) {
+        ukey = active_flows[i];
+
+        /* Both input and output netdevs must be available for the flow */
+        if (!ukey->in_netdev || !ukey->out_netdev) {
+            continue;
+        }
+
+        /* Get input netdev for the flow */
+        netdev = ukey->tunnel_netdev ? ukey->tunnel_netdev : ukey->in_netdev;
+
+        /* Is the in-netdev for this flow in OOR state ? */
+        if (netdev->hw_info.oor) {
+            /* Add the flow to sort_flows[] */
+            sort_flows[total_flow_count++] = active_flows[i];
+
+            if (ukey->offloaded) {
+                total_offload_count++;
+                if (netdev->hw_info.offload_count++ == 0) {
+                    oor_netdev_count++;
+                }
+            } else {
+                total_pending_count++;
+                netdev->hw_info.pending_count++;
+            }
+        }
+    }
+
+    qsort(sort_flows, total_flow_count, sizeof(struct udpif_key *),
+          flow_compare_rebalance);
+
+    /*
+     * We now have a count of offloaded and pending flows on each of the
+     * netdevs that are in OOR state. Now rebalance netdevs that are in OOR
+     * state.
+     */
+    while (oor_netdev_count) {
+        netdev = sort_flows[offload_index]->tunnel_netdev ?
+                         sort_flows[offload_index]->tunnel_netdev :
+                         sort_flows[offload_index]->in_netdev;
+        if (!netdev->hw_info.oor) {
+                continue;
+        }
+
+        VLOG_DBG("Offload rebalance: netdev: %s is OOR\n", netdev->name);
+        pending_index = offload_index + netdev->hw_info.offload_count;
+        oor = rebalance_device(udpif,
+                               &sort_flows[offload_index],
+                               netdev->hw_info.offload_count,
+                               &sort_flows[pending_index],
+                               netdev->hw_info.pending_count);
+
+        netdev->hw_info.oor = oor;
+        offload_index = pending_index + netdev->hw_info.pending_count;
+        netdev->hw_info.offload_count = netdev->hw_info.pending_count = 0;
+        oor_netdev_count--;
+    }
+
+    free(sort_flows);
+    free(active_flows);
+}
+
+static void
+ukey_to_ukey_op(struct udpif *udpif, struct ukey_op *uop,
+                struct udpif_key *ukey, bool put)
+{
+    if (put) {
+        put_op_init(uop, ukey, DPIF_FP_CREATE);
+    } else {
+        delete_op_init(udpif, uop, ukey);
+    }
+}
+
+#define FLOW_PGM_NUM_OPS 1
+
+static int
+udpif_flow_program(struct udpif *udpif, struct udpif_key *ukey,
+                   enum dpif_op_skip_type skip_flag)
+{
+    struct dpif_op *opsp;
+    struct ukey_op uop;
+
+    opsp = &uop.dop;
+    ukey_to_ukey_op(udpif, &uop, ukey, true);
+    dpif_operate(udpif->dpif, &opsp, FLOW_PGM_NUM_OPS, skip_flag);
+
+    return opsp->error;
+}
+
+static int
+udpif_flow_unprogram(struct udpif *udpif, struct udpif_key *ukey,
+                     enum dpif_op_skip_type skip_flag)
+{
+    struct dpif_op *opsp;
+    struct ukey_op uop;
+
+    opsp = &uop.dop;
+    ukey_to_ukey_op(udpif, &uop, ukey, false);
+    dpif_operate(udpif->dpif, &opsp, FLOW_PGM_NUM_OPS, skip_flag);
+
+    return opsp->error;
+}