Maybe it's a bit late for this series, but would be possible in a
future enhancement to have a user parameter to set a different value
for ALB_PMD_LOAD_THRESHOLD?

Regards,
Federico

FEDERICO IEZZI

SR. TELCO ARCHITECT

Red Hat EMEA

fie...@redhat.com    M: +31-6-5152-9709

TRIED. TESTED. TRUSTED.
@RedHat   Red Hat   Red Hat


On Mon, 14 Jan 2019 at 11:56, Nitin Katiyar <nitin.kati...@ericsson.com> wrote:
>
> Port rx queues that have not been statically assigned to PMDs are currently
> assigned based on periodically sampled load measurements.
> The assignment is performed at specific instances – port addition, port
> deletion, upon reassignment request via CLI etc.
>
> Due to change in traffic pattern over time it can cause uneven load among
> the PMDs and thus resulting in lower overall throughout.
>
> This patch enables the support of auto load balancing of PMDs based on
> measured load of RX queues. Each PMD measures the processing load for each
> of its associated queues every 10 seconds. If the aggregated PMD load reaches
> 95% for 6 consecutive intervals then PMD considers itself to be overloaded.
>
> If any PMD is overloaded, a dry-run of the PMD assignment algorithm is
> performed by OVS main thread. The dry-run does NOT change the existing
> queue to PMD assignments.
>
> If the resultant mapping of dry-run indicates an improved distribution
> of the load then the actual reassignment will be performed.
>
> The automatic rebalancing will be disabled by default and has to be
> enabled via configuration option. The interval (in minutes) between
> two consecutive rebalancing can also be configured via CLI, default
> is 1 min.
>
> Following example commands can be used to set the auto-lb params:
> ovs-vsctl set open_vswitch . other_config:pmd-auto-lb="true"
> ovs-vsctl set open_vswitch . other_config:pmd-auto-lb-rebalance-intvl="5"
>
> Co-authored-by: Rohith Basavaraja <rohith.basavar...@gmail.com>
> Co-authored-by: Venkatesan Pradeep <venkatesan.prad...@ericsson.com>
> Signed-off-by: Rohith Basavaraja <rohith.basavar...@gmail.com>
> Signed-off-by: Venkatesan Pradeep <venkatesan.prad...@ericsson.com>
> Signed-off-by: Nitin Katiyar <nitin.kati...@ericsson.com>
> ---
>  Documentation/topics/dpdk/pmd.rst |  41 +++++
>  NEWS                              |   1 +
>  lib/dpif-netdev.c                 | 379 
> ++++++++++++++++++++++++++++++++++++++
>  vswitchd/vswitch.xml              |  41 +++++
>  4 files changed, 462 insertions(+)
>
> diff --git a/Documentation/topics/dpdk/pmd.rst 
> b/Documentation/topics/dpdk/pmd.rst
> index dd9172d..c273b40 100644
> --- a/Documentation/topics/dpdk/pmd.rst
> +++ b/Documentation/topics/dpdk/pmd.rst
> @@ -183,3 +183,44 @@ or can be triggered by using::
>     In addition, the output of ``pmd-rxq-show`` was modified to include
>     Rx queue utilization of the PMD as a percentage. Prior to this, tracking 
> of
>     stats was not available.
> +
> +Automatic assignment of Port/Rx Queue to PMD Threads (experimental)
> +-------------------------------------------------------------------
> +
> +Cycle or utilization based allocation of Rx queues to PMDs gives efficient
> +load distribution but it is not adaptive to change in traffic pattern 
> occuring
> +over the time. This causes uneven load among the PMDs which results in 
> overall
> +lower throughput.
> +
> +To address this automatic load balancing of PMDs can be set by::
> +
> +    $ ovs-vsctl set open_vswitch . other_config:pmd-auto-lb="true"
> +
> +If pmd-auto-lb is set to true AND cycle based assignment is enabled then auto
> +load balancing of PMDs is enabled provided there are 2 or more non-isolated
> +PMDs and at least one of these PMDs is polling more than one RX queue.
> +
> +Once auto load balancing is set, each non-isolated PMD measures the 
> processing
> +load for each of its associated queues every 10 seconds. If the aggregated 
> PMD
> +load reaches 95% for 6 consecutive intervals then PMD considers itself to be
> +overloaded.
> +
> +If any PMD is overloaded, a dry-run of the PMD assignment algorithm is
> +performed by OVS main thread. The dry-run does NOT change the existing queue
> +to PMD assignments.
> +
> +If the resultant mapping of dry-run indicates an improved distribution of the
> +load then the actual reassignment will be performed.
> +
> +The minimum time between 2 consecutive PMD auto load balancing iterations can
> +also be configured by::
> +
> +    $ ovs-vsctl set open_vswitch .\
> +        other_config:pmd-auto-lb-rebal-interval="<interval>"
> +
> +where ``<interval>`` is a value in minutes. The default interval is 1 minute
> +and setting it to 0 will also result in default value i.e. 1 min.
> +
> +A user can use this option to avoid frequent trigger of auto load balancing 
> of
> +PMDs. For e.g. set this (in min) such that it occurs once in few hours or a 
> day
> +or a week.
> diff --git a/NEWS b/NEWS
> index 2de844f..0e9fcb1 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -23,6 +23,7 @@ Post-v2.10.0
>       * Add option for simple round-robin based Rxq to PMD assignment.
>         It can be set with pmd-rxq-assign.
>       * Add support for DPDK 18.11
> +     * Add support for Auto load balancing of PMDs (experimental)
>     - Add 'symmetric_l3' hash function.
>     - OVS now honors 'updelay' and 'downdelay' for bonds with LACP configured.
>     - ovs-vswitchd:
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index 1564db9..c1757ab 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -80,6 +80,12 @@
>
>  VLOG_DEFINE_THIS_MODULE(dpif_netdev);
>
> +/* Auto Load Balancing Defaults */
> +#define ALB_ACCEPTABLE_IMPROVEMENT       25
> +#define ALB_PMD_LOAD_THRESHOLD           95
> +#define ALB_PMD_REBALANCE_POLL_INTERVAL  1 /* 1 Min */
> +#define MIN_TO_MSEC                  60000
> +
>  #define FLOW_DUMP_MAX_BATCH 50
>  /* Use per thread recirc_depth to prevent recirculation loop. */
>  #define MAX_RECIRC_DEPTH 6
> @@ -288,6 +294,13 @@ struct dp_meter {
>      struct dp_meter_band bands[];
>  };
>
> +struct pmd_auto_lb {
> +    bool auto_lb_requested;     /* Auto load balancing requested by user. */
> +    bool is_enabled;            /* Current status of Auto load balancing. */
> +    uint64_t rebalance_intvl;
> +    uint64_t rebalance_poll_timer;
> +};
> +
>  /* Datapath based on the network device interface from netdev.h.
>   *
>   *
> @@ -368,6 +381,7 @@ struct dp_netdev {
>      uint64_t last_tnl_conf_seq;
>
>      struct conntrack conntrack;
> +    struct pmd_auto_lb pmd_alb;
>  };
>
>  static void meter_lock(const struct dp_netdev *dp, uint32_t meter_id)
> @@ -702,6 +716,11 @@ struct dp_netdev_pmd_thread {
>      /* Keep track of detailed PMD performance statistics. */
>      struct pmd_perf_stats perf_stats;
>
> +    /* Stats from previous iteration used by automatic pmd
> +     * load balance logic. */
> +    uint64_t prev_stats[PMD_N_STATS];
> +    atomic_count pmd_overloaded;
> +
>      /* Set to true if the pmd thread needs to be reloaded. */
>      bool need_reload;
>  };
> @@ -3734,6 +3753,53 @@ dpif_netdev_operate(struct dpif *dpif, struct dpif_op 
> **ops, size_t n_ops,
>      }
>  }
>
> +/* Enable or Disable PMD auto load balancing. */
> +static void
> +set_pmd_auto_lb(struct dp_netdev *dp)
> +{
> +    unsigned int cnt = 0;
> +    struct dp_netdev_pmd_thread *pmd;
> +    struct pmd_auto_lb *pmd_alb = &dp->pmd_alb;
> +
> +    bool enable_alb = false;
> +    bool multi_rxq = false;
> +    bool pmd_rxq_assign_cyc = dp->pmd_rxq_assign_cyc;
> +
> +    /* Ensure that there is at least 2 non-isolated PMDs and
> +     * one of them is polling more than one rxq. */
> +    CMAP_FOR_EACH (pmd, node, &dp->poll_threads) {
> +        if (pmd->core_id == NON_PMD_CORE_ID || pmd->isolated) {
> +            continue;
> +        }
> +
> +        if (hmap_count(&pmd->poll_list) > 1) {
> +            multi_rxq = true;
> +        }
> +        if (cnt && multi_rxq) {
> +                enable_alb = true;
> +                break;
> +        }
> +        cnt++;
> +    }
> +
> +    /* Enable auto LB if it is requested and cycle based assignment is true. 
> */
> +    enable_alb = enable_alb && pmd_rxq_assign_cyc &&
> +                    pmd_alb->auto_lb_requested;
> +
> +    if (pmd_alb->is_enabled != enable_alb) {
> +        pmd_alb->is_enabled = enable_alb;
> +        if (pmd_alb->is_enabled) {
> +            VLOG_INFO("PMD auto load balance is enabled "
> +                      "(with rebalance interval:%"PRIu64" msec)",
> +                       pmd_alb->rebalance_intvl);
> +        } else {
> +            pmd_alb->rebalance_poll_timer = 0;
> +            VLOG_INFO("PMD auto load balance is disabled");
> +        }
> +    }
> +
> +}
> +
>  /* Applies datapath configuration from the database. Some of the changes are
>   * actually applied in dpif_netdev_run(). */
>  static int
> @@ -3748,6 +3814,7 @@ dpif_netdev_set_config(struct dpif *dpif, const struct 
> smap *other_config)
>                          DEFAULT_EM_FLOW_INSERT_INV_PROB);
>      uint32_t insert_min, cur_min;
>      uint32_t tx_flush_interval, cur_tx_flush_interval;
> +    uint64_t rebalance_intvl;
>
>      tx_flush_interval = smap_get_int(other_config, "tx-flush-interval",
>                                       DEFAULT_TX_FLUSH_INTERVAL);
> @@ -3819,6 +3886,23 @@ dpif_netdev_set_config(struct dpif *dpif, const struct 
> smap *other_config)
>                    pmd_rxq_assign);
>          dp_netdev_request_reconfigure(dp);
>      }
> +
> +    struct pmd_auto_lb *pmd_alb = &dp->pmd_alb;
> +    pmd_alb->auto_lb_requested = smap_get_bool(other_config, "pmd-auto-lb",
> +                              false);
> +
> +    rebalance_intvl = smap_get_int(other_config, 
> "pmd-auto-lb-rebal-interval",
> +                              ALB_PMD_REBALANCE_POLL_INTERVAL);
> +
> +    /* Input is in min, convert it to msec. */
> +    rebalance_intvl =
> +        rebalance_intvl ? rebalance_intvl * MIN_TO_MSEC : MIN_TO_MSEC;
> +
> +    if (pmd_alb->rebalance_intvl != rebalance_intvl) {
> +        pmd_alb->rebalance_intvl = rebalance_intvl;
> +    }
> +
> +    set_pmd_auto_lb(dp);
>      return 0;
>  }
>
> @@ -4762,6 +4846,9 @@ reconfigure_datapath(struct dp_netdev *dp)
>
>      /* Reload affected pmd threads. */
>      reload_affected_pmds(dp);
> +
> +    /* Check if PMD Auto LB is to be enabled */
> +    set_pmd_auto_lb(dp);
>  }
>
>  /* Returns true if one of the netdevs in 'dp' requires a reconfiguration */
> @@ -4780,6 +4867,237 @@ ports_require_restart(const struct dp_netdev *dp)
>      return false;
>  }
>
> +/* Function for calculating variance. */
> +static uint64_t
> +variance(uint64_t a[], int n)
> +{
> +    /* Compute mean (average of elements). */
> +    uint64_t sum = 0;
> +    uint64_t mean = 0;
> +    uint64_t sqDiff = 0;
> +
> +    if (!n) {
> +        return 0;
> +    }
> +
> +    for (int i = 0; i < n; i++) {
> +        sum += a[i];
> +    }
> +
> +    if (sum) {
> +        mean = sum / n;
> +
> +        /* Compute sum squared differences with mean. */
> +        for (int i = 0; i < n; i++) {
> +            sqDiff += (a[i] - mean)*(a[i] - mean);
> +        }
> +    }
> +    return (sqDiff ? (sqDiff / n) : 0);
> +}
> +
> +
> +/* Returns the variance in the PMDs usage as part of dry run of rxqs
> + * assignment to PMDs. */
> +static bool
> +get_dry_run_variance(struct dp_netdev *dp, uint32_t *core_list,
> +                     uint32_t num, uint64_t *predicted_variance)
> +    OVS_REQUIRES(dp->port_mutex)
> +{
> +    struct dp_netdev_port *port;
> +    struct dp_netdev_pmd_thread *pmd;
> +    struct dp_netdev_rxq ** rxqs = NULL;
> +    struct rr_numa *numa = NULL;
> +    struct rr_numa_list rr;
> +    int n_rxqs = 0;
> +    bool ret = false;
> +    uint64_t *pmd_usage;
> +
> +    if (!predicted_variance) {
> +        return ret;
> +    }
> +
> +    pmd_usage = xcalloc(num, sizeof(uint64_t));
> +
> +    HMAP_FOR_EACH (port, node, &dp->ports) {
> +        if (!netdev_is_pmd(port->netdev)) {
> +            continue;
> +        }
> +
> +        for (int qid = 0; qid < port->n_rxq; qid++) {
> +            struct dp_netdev_rxq *q = &port->rxqs[qid];
> +            uint64_t cycle_hist = 0;
> +
> +            if (q->pmd->isolated) {
> +                continue;
> +            }
> +
> +            if (n_rxqs == 0) {
> +                rxqs = xmalloc(sizeof *rxqs);
> +            } else {
> +                rxqs = xrealloc(rxqs, sizeof *rxqs * (n_rxqs + 1));
> +            }
> +
> +            /* Sum the queue intervals and store the cycle history. */
> +            for (unsigned i = 0; i < PMD_RXQ_INTERVAL_MAX; i++) {
> +                cycle_hist += dp_netdev_rxq_get_intrvl_cycles(q, i);
> +            }
> +            dp_netdev_rxq_set_cycles(q, RXQ_CYCLES_PROC_HIST,
> +                                         cycle_hist);
> +            /* 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, compare_rxq_cycles);
> +    }
> +    rr_numa_list_populate(dp, &rr);
> +
> +    for (int i = 0; i < n_rxqs; i++) {
> +        int numa_id = netdev_get_numa_id(rxqs[i]->port->netdev);
> +        numa = rr_numa_list_lookup(&rr, numa_id);
> +        if (!numa) {
> +            /* Abort if cross NUMA polling. */
> +            VLOG_DBG("PMD auto lb dry run."
> +                     " Aborting due to cross-numa polling.");
> +            goto cleanup;
> +        }
> +
> +        pmd = rr_numa_get_pmd(numa, true);
> +        VLOG_DBG("PMD auto lb dry run. Predicted: Core %d on numa node %d "
> +                  "to be assigned port \'%s\' rx queue %d "
> +                  "(measured processing cycles %"PRIu64").",
> +                  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_HIST));
> +
> +        for (int id = 0; id < num; id++) {
> +            if (pmd->core_id == core_list[id]) {
> +                /* Add the processing cycles of rxq to pmd polling it. */
> +                pmd_usage[id] += dp_netdev_rxq_get_cycles(rxqs[i],
> +                                        RXQ_CYCLES_PROC_HIST);
> +            }
> +        }
> +    }
> +
> +    CMAP_FOR_EACH (pmd, node, &dp->poll_threads) {
> +        uint64_t total_cycles = 0;
> +
> +        if ((pmd->core_id == NON_PMD_CORE_ID) || pmd->isolated) {
> +            continue;
> +        }
> +
> +        /* Get the total pmd cycles for an interval. */
> +        atomic_read_relaxed(&pmd->intrvl_cycles, &total_cycles);
> +        /* Estimate the cycles to cover all intervals. */
> +        total_cycles *= PMD_RXQ_INTERVAL_MAX;
> +        for (int id = 0; id < num; id++) {
> +            if (pmd->core_id == core_list[id]) {
> +                if (pmd_usage[id]) {
> +                    pmd_usage[id] = (pmd_usage[id] * 100) / total_cycles;
> +                }
> +                VLOG_DBG("PMD auto lb dry run. Predicted: Core %d, "
> +                         "usage %"PRIu64"", pmd->core_id, pmd_usage[id]);
> +            }
> +        }
> +    }
> +    *predicted_variance = variance(pmd_usage, num);
> +    ret = true;
> +
> +cleanup:
> +    rr_numa_list_destroy(&rr);
> +    free(rxqs);
> +    free(pmd_usage);
> +    return ret;
> +}
> +
> +/* Does the dry run of Rxq assignment to PMDs and returns true if it gives
> + * better distribution of load on PMDs. */
> +static bool
> +pmd_rebalance_dry_run(struct dp_netdev *dp)
> +    OVS_REQUIRES(dp->port_mutex)
> +{
> +    struct dp_netdev_pmd_thread *pmd;
> +    uint64_t *curr_pmd_usage;
> +
> +    uint64_t curr_variance;
> +    uint64_t new_variance;
> +    uint64_t improvement = 0;
> +    uint32_t num_pmds;
> +    uint32_t *pmd_corelist;
> +    struct rxq_poll *poll, *poll_next;
> +    bool ret;
> +
> +    num_pmds = cmap_count(&dp->poll_threads);
> +
> +    if (num_pmds > 1) {
> +        curr_pmd_usage = xcalloc(num_pmds, sizeof(uint64_t));
> +        pmd_corelist = xcalloc(num_pmds, sizeof(uint32_t));
> +    } else {
> +        return false;
> +    }
> +
> +    num_pmds = 0;
> +    CMAP_FOR_EACH (pmd, node, &dp->poll_threads) {
> +        uint64_t total_cycles = 0;
> +        uint64_t total_proc = 0;
> +
> +        if ((pmd->core_id == NON_PMD_CORE_ID) || pmd->isolated) {
> +            continue;
> +        }
> +
> +        /* Get the total pmd cycles for an interval. */
> +        atomic_read_relaxed(&pmd->intrvl_cycles, &total_cycles);
> +        /* Estimate the cycles to cover all intervals. */
> +        total_cycles *= PMD_RXQ_INTERVAL_MAX;
> +
> +        HMAP_FOR_EACH_SAFE (poll, poll_next, node, &pmd->poll_list) {
> +            uint64_t proc_cycles = 0;
> +            for (unsigned i = 0; i < PMD_RXQ_INTERVAL_MAX; i++) {
> +                proc_cycles += dp_netdev_rxq_get_intrvl_cycles(poll->rxq, i);
> +            }
> +            total_proc += proc_cycles;
> +        }
> +        if (total_proc) {
> +            curr_pmd_usage[num_pmds] = (total_proc * 100) / total_cycles;
> +        }
> +
> +        VLOG_DBG("PMD auto lb dry run. Current: Core %d, usage %"PRIu64"",
> +                  pmd->core_id, curr_pmd_usage[num_pmds]);
> +
> +        if (atomic_count_get(&pmd->pmd_overloaded)) {
> +            atomic_count_set(&pmd->pmd_overloaded, 0);
> +        }
> +
> +        pmd_corelist[num_pmds] = pmd->core_id;
> +        num_pmds++;
> +    }
> +
> +    curr_variance = variance(curr_pmd_usage, num_pmds);
> +    ret = get_dry_run_variance(dp, pmd_corelist, num_pmds, &new_variance);
> +
> +    if (ret) {
> +        VLOG_DBG("PMD auto lb dry run. Current PMD variance: %"PRIu64","
> +                  " Predicted PMD variance: %"PRIu64"",
> +                  curr_variance, new_variance);
> +
> +        if (new_variance < curr_variance) {
> +            improvement =
> +                ((curr_variance - new_variance) * 100) / curr_variance;
> +        }
> +        if (improvement < ALB_ACCEPTABLE_IMPROVEMENT) {
> +            ret = false;
> +        }
> +    }
> +
> +    free(curr_pmd_usage);
> +    free(pmd_corelist);
> +    return ret;
> +}
> +
> +
>  /* Return true if needs to revalidate datapath flows. */
>  static bool
>  dpif_netdev_run(struct dpif *dpif)
> @@ -4789,6 +5107,9 @@ dpif_netdev_run(struct dpif *dpif)
>      struct dp_netdev_pmd_thread *non_pmd;
>      uint64_t new_tnl_seq;
>      bool need_to_flush = true;
> +    bool pmd_rebalance = false;
> +    long long int now = time_msec();
> +    struct dp_netdev_pmd_thread *pmd;
>
>      ovs_mutex_lock(&dp->port_mutex);
>      non_pmd = dp_netdev_get_pmd(dp, NON_PMD_CORE_ID);
> @@ -4821,6 +5142,32 @@ dpif_netdev_run(struct dpif *dpif)
>          dp_netdev_pmd_unref(non_pmd);
>      }
>
> +    struct pmd_auto_lb *pmd_alb = &dp->pmd_alb;
> +    if (pmd_alb->is_enabled) {
> +        if (!pmd_alb->rebalance_poll_timer) {
> +            pmd_alb->rebalance_poll_timer = now;
> +        } else if ((pmd_alb->rebalance_poll_timer +
> +                   pmd_alb->rebalance_intvl) < now) {
> +            pmd_alb->rebalance_poll_timer = now;
> +            CMAP_FOR_EACH (pmd, node, &dp->poll_threads) {
> +                if (atomic_count_get(&pmd->pmd_overloaded) >=
> +                                    PMD_RXQ_INTERVAL_MAX) {
> +                    pmd_rebalance = true;
> +                    break;
> +                }
> +            }
> +
> +            if (pmd_rebalance &&
> +                !dp_netdev_is_reconf_required(dp) &&
> +                !ports_require_restart(dp) &&
> +                pmd_rebalance_dry_run(dp)) {
> +                VLOG_INFO("PMD auto lb dry run."
> +                          " requesting datapath reconfigure.");
> +                dp_netdev_request_reconfigure(dp);
> +            }
> +        }
> +    }
> +
>      if (dp_netdev_is_reconf_required(dp) || ports_require_restart(dp)) {
>          reconfigure_datapath(dp);
>      }
> @@ -4979,6 +5326,8 @@ pmd_thread_main(void *f_)
>  reload:
>      pmd_alloc_static_tx_qid(pmd);
>
> +    atomic_count_init(&pmd->pmd_overloaded, 0);
> +
>      /* List port/core affinity */
>      for (i = 0; i < poll_cnt; i++) {
>         VLOG_DBG("Core %d processing port \'%s\' with queue-id %d\n",
> @@ -7188,9 +7537,39 @@ dp_netdev_pmd_try_optimize(struct dp_netdev_pmd_thread 
> *pmd,
>                             struct polled_queue *poll_list, int poll_cnt)
>  {
>      struct dpcls *cls;
> +    uint64_t tot_idle = 0, tot_proc = 0;
> +    unsigned int pmd_load = 0;
>
>      if (pmd->ctx.now > pmd->rxq_next_cycle_store) {
>          uint64_t curr_tsc;
> +        struct pmd_auto_lb *pmd_alb = &pmd->dp->pmd_alb;
> +        if (pmd_alb->is_enabled && !pmd->isolated
> +            && (pmd->perf_stats.counters.n[PMD_CYCLES_ITER_IDLE] >=
> +                                       pmd->prev_stats[PMD_CYCLES_ITER_IDLE])
> +            && (pmd->perf_stats.counters.n[PMD_CYCLES_ITER_BUSY] >=
> +                                        
> pmd->prev_stats[PMD_CYCLES_ITER_BUSY]))
> +            {
> +            tot_idle = pmd->perf_stats.counters.n[PMD_CYCLES_ITER_IDLE] -
> +                       pmd->prev_stats[PMD_CYCLES_ITER_IDLE];
> +            tot_proc = pmd->perf_stats.counters.n[PMD_CYCLES_ITER_BUSY] -
> +                       pmd->prev_stats[PMD_CYCLES_ITER_BUSY];
> +
> +            if (tot_proc) {
> +                pmd_load = ((tot_proc * 100) / (tot_idle + tot_proc));
> +            }
> +
> +            if (pmd_load >= ALB_PMD_LOAD_THRESHOLD) {
> +                atomic_count_inc(&pmd->pmd_overloaded);
> +            } else {
> +                atomic_count_set(&pmd->pmd_overloaded, 0);
> +            }
> +        }
> +
> +        pmd->prev_stats[PMD_CYCLES_ITER_IDLE] =
> +                        pmd->perf_stats.counters.n[PMD_CYCLES_ITER_IDLE];
> +        pmd->prev_stats[PMD_CYCLES_ITER_BUSY] =
> +                        pmd->perf_stats.counters.n[PMD_CYCLES_ITER_BUSY];
> +
>          /* Get the cycles that were used to process each queue and store. */
>          for (unsigned i = 0; i < poll_cnt; i++) {
>              uint64_t rxq_cyc_curr = 
> dp_netdev_rxq_get_cycles(poll_list[i].rxq,
> diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
> index 2160910..72f5283 100644
> --- a/vswitchd/vswitch.xml
> +++ b/vswitchd/vswitch.xml
> @@ -574,6 +574,47 @@
>              be set to 'skip_sw'.
>          </p>
>        </column>
> +      <column name="other_config" key="pmd-auto-lb"
> +              type='{"type": "boolean"}'>
> +        <p>
> +         Configures PMD Auto Load Balancing that allows automatic assignment 
> of
> +         RX queues to PMDs if any of PMDs is overloaded (i.e. processing 
> cycles
> +         > 95%).
> +        </p>
> +        <p>
> +         It uses current scheme of cycle based assignment of RX queues that
> +         are not statically pinned to PMDs.
> +        </p>
> +        <p>
> +          The default value is <code>false</code>.
> +        </p>
> +        <p>
> +          Set this value to <code>true</code> to enable this option. It is
> +          currently disabled by default and an experimental feature.
> +        </p>
> +        <p>
> +         This only comes in effect if cycle based assignment is enabled and
> +         there are more than one non-isolated PMDs present and atleast one of
> +         it polls more than one queue.
> +        </p>
> +      </column>
> +      <column name="other_config" key="pmd-auto-lb-rebal-interval"
> +              type='{"type": "integer",
> +                     "minInteger": 0, "maxInteger": 20000}'>
> +        <p>
> +         The minimum time (in minutes) 2 consecutive PMD Auto Load Balancing
> +         iterations.
> +        </p>
> +        <p>
> +         The defaul value is 1 min. If configured to 0 then it would be
> +         converted to default value i.e. 1 min
> +        </p>
> +        <p>
> +         This option can be configured to avoid frequent trigger of auto load
> +         balancing of PMDs. For e.g. set the value (in min) such that it 
> occurs
> +         once in few hours or a day or a week.
> +        </p>
> +      </column>
>      </group>
>      <group title="Status">
>        <column name="next_cfg">
> --
> 1.9.1
>
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