[ovs-dev] [PATCH v2] dpif-netdev: proper tx queue id

Ilya Maximets i.maximets at samsung.com
Tue Aug 18 14:03:22 UTC 2015


Thanks for review.
I sent new version of patch.

http://openvswitch.org/pipermail/dev/2015-August/058926.html

Best regards, Ilya Maximets.

On 17.08.2015 19:45, Daniele Di Proietto wrote:
> Sorry about the long wait.
> 
> I think this is the right direction, I like the idea of having a thread
> local map of the txqs.  It will allow us to assign the txqs in a more
> sophisticated way.
> 
> I see some unit tests failing with this patch applied.  Could you try
> running the testsuite with 'make check'?
> 
> The txq distribution code is run only when a pmd device is added.
> If a "system" or a "dummy" device is added its txq will not be used
> by any pmd thread (or to the main thread).
> 
> Two more comments below.
> 
> On 06/08/2015 15:32, "Ilya Maximets" <i.maximets at samsung.com> wrote:
> 
>> Currently tx_qid is equal to pmd->core_id. This leads to unexpected
>> behavior if pmd-cpu-mask different from '/(0*)(1|3|7)?(f*)/',
>> e.g. if core_ids are not sequential, or doesn't start from 0, or both.
>>
>> Example:
>> 	starting 2 pmd threads with 1 port, 2 rxqs per port,
>> 	pmd-cpu-mask = 00000014 and let dev->real_n_txq = 2
>>
>> 	It that case pmd_1->tx_qid = 2, pmd_2->tx_qid = 4 and
>> 	txq_needs_locking = true (if device hasn't ovs_numa_get_n_cores()+1
>> 	queues).
>>
>> 	In that case, after truncating in netdev_dpdk_send__():
>> 		'qid = qid % dev->real_n_txq;'
>> 	pmd_1: qid = 2 % 2 = 0
>> 	pmd_2: qid = 4 % 2 = 0
>>
>> 	So, both threads will call dpdk_queue_pkts() with same qid = 0.
>> 	This is unexpected behavior if there is 2 tx queues in device.
>> 	Queue #1 will not be used and both threads will lock queue #0
>> 	on each send.
>>
>> Fix that by introducing per pmd thread hash map 'tx_queues', where will
>> be stored all available tx queues for that pmd thread with
>> port_no as a key(hash). All tx_qid-s will be unique per port and
>> sequential to prevent described unexpected mapping after truncating.
>>
>> Implemented infrastructure can be used in the future to choose
>> between all tx queues available for that pmd thread.
>>
>> Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
>> ---
>> lib/dpif-netdev.c | 110
>> ++++++++++++++++++++++++++++++++++++++++++++----------
>> 1 file changed, 91 insertions(+), 19 deletions(-)
>>
>> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
>> index c144352..309994c 100644
>> --- a/lib/dpif-netdev.c
>> +++ b/lib/dpif-netdev.c
>> @@ -365,6 +365,13 @@ struct dp_netdev_pmd_cycles {
>>     atomic_ullong n[PMD_N_CYCLES];
>> };
>>
>> +struct dp_netdev_pmd_txq {
>> +    struct cmap_node node;        /* In owning dp_netdev_pmd_thread's */
>> +                                  /* 'tx_queues'. */
>> +    struct dp_netdev_port *port;
>> +    int tx_qid;
>> +};
>> +
>> /* PMD: Poll modes drivers.  PMD accesses devices via polling to
>> eliminate
>>  * the performance overhead of interrupt processing.  Therefore netdev
>> can
>>  * not implement rx-wait for these devices.  dpif-netdev needs to poll
>> @@ -420,8 +427,8 @@ struct dp_netdev_pmd_thread {
>>                                     /* threads on same numa node. */
>>     unsigned core_id;               /* CPU core id of this pmd thread. */
>>     int numa_id;                    /* numa node id of this pmd thread.
>> */
>> -    int tx_qid;                     /* Queue id used by this pmd thread
>> to
>> -                                     * send packets on all netdevs */
>> +    struct cmap tx_queues;          /* Queue ids used by this pmd thread
>> to
>> +                                     * send packets to ports */
>>
>>     /* Only a pmd thread can write on its own 'cycles' and 'stats'.
>>      * The main thread keeps 'stats_zero' and 'cycles_zero' as base
>> @@ -2602,6 +2609,46 @@ dpif_netdev_wait(struct dpif *dpif)
>>     seq_wait(tnl_conf_seq, dp->last_tnl_conf_seq);
>> }
>>
>> +static void
>> +pmd_flush_tx_queues(struct dp_netdev_pmd_thread *pmd)
>> +{
>> +    struct dp_netdev_pmd_txq *txq;
>> +
>> +    CMAP_FOR_EACH (txq, node, &pmd->tx_queues) {
>> +        cmap_remove(&pmd->tx_queues, &txq->node,
>> +                    hash_port_no(txq->port->port_no));
>> +        port_unref(txq->port);
>> +        free(txq);
>> +    }
>> +}
> 
> The term "flush" used for txqs makes me think that the
> packets in the device transmission queue will be sent.
> 
>> +
>> +static void OVS_UNUSED
>> +pmd_tx_queues_print(struct dp_netdev_pmd_thread *pmd)
>> +{
>> +    struct dp_netdev_pmd_txq *txq;
>> +
>> +    CMAP_FOR_EACH (txq, node, &pmd->tx_queues) {
>> +        VLOG_INFO("Core_id: %d, Port: %s, tx_qid: %d\n",
>> +                   pmd->core_id, netdev_get_name(txq->port->netdev),
>> +                   txq->tx_qid);
>> +    }
>> +}
>> +
>> +static struct dp_netdev_pmd_txq *
>> +pmd_lookup_txq(const struct dp_netdev_pmd_thread *pmd,
>> +               const struct dp_netdev_port *port)
>> +{
>> +    struct dp_netdev_pmd_txq *txq;
>> +
>> +    CMAP_FOR_EACH_WITH_HASH (txq, node, hash_port_no(port->port_no),
>> +                             &pmd->tx_queues) {
>> +        if (txq->port == port) {
>> +            return txq;
>> +        }
>> +    }
>> +    return NULL;
>> +}
>> +
>> struct rxq_poll {
>>     struct dp_netdev_port *port;
>>     struct netdev_rxq *rx;
>> @@ -2613,16 +2660,20 @@ pmd_load_queues(struct dp_netdev_pmd_thread *pmd,
>> {
>>     struct rxq_poll *poll_list = *ppoll_list;
>>     struct dp_netdev_port *port;
>> -    int n_pmds_on_numa, index, i;
>> +    struct dp_netdev_pmd_txq *txq;
>> +    int n_pmds_on_numa, rx_index, tx_index, i;
>>
>>     /* Simple scheduler for netdev rx polling. */
>> +    pmd_flush_tx_queues(pmd);
>> +
>>     for (i = 0; i < poll_cnt; i++) {
>>         port_unref(poll_list[i].port);
>>     }
>>
>>     poll_cnt = 0;
>>     n_pmds_on_numa = get_n_pmd_threads_on_numa(pmd->dp, pmd->numa_id);
>> -    index = 0;
>> +    rx_index = 0;
>> +    tx_index = 0;
>>
>>     CMAP_FOR_EACH (port, node, &pmd->dp->ports) {
>>         /* Calls port_try_ref() to prevent the main thread
>> @@ -2633,7 +2684,7 @@ pmd_load_queues(struct dp_netdev_pmd_thread *pmd,
>>                 int i;
>>
>>                 for (i = 0; i < netdev_n_rxq(port->netdev); i++) {
>> -                    if ((index % n_pmds_on_numa) == pmd->index) {
>> +                    if ((rx_index % n_pmds_on_numa) == pmd->index) {
>>                         poll_list = xrealloc(poll_list,
>>                                         sizeof *poll_list * (poll_cnt +
>> 1));
>>
>> @@ -2642,7 +2693,20 @@ pmd_load_queues(struct dp_netdev_pmd_thread *pmd,
>>                         poll_list[poll_cnt].rx = port->rxq[i];
>>                         poll_cnt++;
>>                     }
>> -                    index++;
>> +                    rx_index++;
>> +                }
>> +
>> +                /* Last queue reserved for non pmd threads */
>> +                for (i = 0; i < netdev_n_txq(port->netdev) - 1; i++) {
>> +                    if ((tx_index % n_pmds_on_numa) == pmd->index) {
>> +                        txq = xmalloc(sizeof *txq);
>> +                        port_ref(port);
>> +                        txq->port = port;
>> +                        txq->tx_qid = i;
>> +                        cmap_insert(&pmd->tx_queues, &txq->node,
>> +                                    hash_port_no(port->port_no));
>> +                    }
>> +                    tx_index++;
>>                 }
>>             }
>>             /* Unrefs the port_try_ref(). */
>> @@ -2712,6 +2776,8 @@ reload:
>>         goto reload;
>>     }
>>
>> +    pmd_flush_tx_queues(pmd);
>> +
>>     for (i = 0; i < poll_cnt; i++) {
>>          port_unref(poll_list[i].port);
>>     }
>> @@ -2825,16 +2891,6 @@ dp_netdev_pmd_get_next(struct dp_netdev *dp,
>> struct cmap_position *pos)
>>     return next;
>> }
>>
>> -static int
>> -core_id_to_qid(unsigned core_id)
>> -{
>> -    if (core_id != NON_PMD_CORE_ID) {
>> -        return core_id;
>> -    } else {
>> -        return ovs_numa_get_n_cores();
>> -    }
>> -}
>> -
>> /* Configures the 'pmd' based on the input argument. */
>> static void
>> dp_netdev_configure_pmd(struct dp_netdev_pmd_thread *pmd, struct
>> dp_netdev *dp,
>> @@ -2843,7 +2899,6 @@ dp_netdev_configure_pmd(struct dp_netdev_pmd_thread
>> *pmd, struct dp_netdev *dp,
>>     pmd->dp = dp;
>>     pmd->index = index;
>>     pmd->core_id = core_id;
>> -    pmd->tx_qid = core_id_to_qid(core_id);
>>     pmd->numa_id = numa_id;
>>
>>     ovs_refcount_init(&pmd->ref_cnt);
>> @@ -2854,9 +2909,20 @@ dp_netdev_configure_pmd(struct
>> dp_netdev_pmd_thread *pmd, struct dp_netdev *dp,
>>     ovs_mutex_init(&pmd->flow_mutex);
>>     dpcls_init(&pmd->cls);
>>     cmap_init(&pmd->flow_table);
>> -    /* init the 'flow_cache' since there is no
>> +    cmap_init(&pmd->tx_queues);
>> +    /* init the 'flow_cache' and 'tx_queues' since there is no
>>      * actual thread created for NON_PMD_CORE_ID. */
>>     if (core_id == NON_PMD_CORE_ID) {
>> +        struct dp_netdev_port *port;
>> +        CMAP_FOR_EACH (port, node, &pmd->dp->ports) {
>> +            if (port_try_ref(port)) {
>> +                struct dp_netdev_pmd_txq * txq = xmalloc(sizeof *txq);
>> +                txq->port = port;
>> +                txq->tx_qid = ovs_numa_get_n_cores();
>> +                cmap_insert(&pmd->tx_queues, &txq->node,
>> +                            hash_port_no(port->port_no));
>> +            }
>> +        }
>>         emc_cache_init(&pmd->flow_cache);
>>     }
>>     cmap_insert(&dp->poll_threads, CONST_CAST(struct cmap_node *,
>> &pmd->node),
>> @@ -2869,6 +2935,7 @@ dp_netdev_destroy_pmd(struct dp_netdev_pmd_thread
>> *pmd)
>>     dp_netdev_pmd_flow_flush(pmd);
>>     dpcls_destroy(&pmd->cls);
>>     cmap_destroy(&pmd->flow_table);
>> +    cmap_destroy(&pmd->tx_queues);
>>     ovs_mutex_destroy(&pmd->flow_mutex);
>>     latch_destroy(&pmd->exit_latch);
>>     xpthread_cond_destroy(&pmd->cond);
>> @@ -2885,6 +2952,7 @@ dp_netdev_del_pmd(struct dp_netdev_pmd_thread *pmd)
>>      * no actual thread uninit it for NON_PMD_CORE_ID. */
>>     if (pmd->core_id == NON_PMD_CORE_ID) {
>>         emc_cache_uninit(&pmd->flow_cache);
>> +        pmd_flush_tx_queues(pmd);
>>     } else {
>>         latch_set(&pmd->exit_latch);
>>         dp_netdev_reload_pmd__(pmd);
>> @@ -3480,13 +3548,17 @@ dp_execute_cb(void *aux_, struct dp_packet
>> **packets, int cnt,
>>     struct dp_netdev *dp = pmd->dp;
>>     int type = nl_attr_type(a);
>>     struct dp_netdev_port *p;
>> +    struct dp_netdev_pmd_txq *txq;
>>     int i;
>>
>>     switch ((enum ovs_action_attr)type) {
>>     case OVS_ACTION_ATTR_OUTPUT:
>>         p = dp_netdev_lookup_port(dp, u32_to_odp(nl_attr_get_u32(a)));
>>         if (OVS_LIKELY(p)) {
>> -            netdev_send(p->netdev, pmd->tx_qid, packets, cnt, may_steal);
>> +            txq = pmd_lookup_txq(pmd, p);
>> +            if (OVS_UNLIKELY(!txq))
>> +                break;
>> +            netdev_send(p->netdev, txq->tx_qid, packets, cnt, may_steal);
> 
> I think that performing two lookups (for the port and for the txq) is more
> expensive than necessary.  One solution could be to include a pointer to
> the
> netdev in the 'txq'.
> 
>>             return;
>>         }
>>         break;
>> -- 
>> 2.1.4
>>
> 
> 



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