Re: [dpdk-dev] [PATCH v4 6/7] virtio: simple tx routine

["Xie, Huawei" <huawei.xie@intel.com>]

On 10/23/2015 12:57 AM, Stephen Hemminger wrote:
> On Thu, 22 Oct 2015 20:09:50 +0800
> Huawei Xie <huawei.xie@intel.com> wrote:
>
>> Changes in v4:
>> - move virtio_xmit_cleanup ahead to free descriptors earlier
>>
>> Changes in v3:
>> - Remove return at the end of void function
>> - Remove always_inline attribute for virtio_xmit_cleanup
>> bulk free of mbufs when clean used ring.
>> shift operation of idx could be saved if vq_free_cnt means
>> free slots rather than free descriptors.
>>
>> TODO: rearrange vq data structure, pack the stats var together so that we
>> could use one vec instruction to update all of them.
>>
>> Signed-off-by: Huawei Xie <huawei.xie@intel.com>
>> ---
>>  drivers/net/virtio/virtio_ethdev.h      |  3 ++
>>  drivers/net/virtio/virtio_rxtx_simple.c | 93 +++++++++++++++++++++++++++++++++
>>  2 files changed, 96 insertions(+)
>>
>> diff --git a/drivers/net/virtio/virtio_ethdev.h b/drivers/net/virtio/virtio_ethdev.h
>> index d7797ab..ae2d47d 100644
>> --- a/drivers/net/virtio/virtio_ethdev.h
>> +++ b/drivers/net/virtio/virtio_ethdev.h
>> @@ -111,6 +111,9 @@ uint16_t virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
>>  uint16_t virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
>>  		uint16_t nb_pkts);
>>  
>> +uint16_t virtio_xmit_pkts_simple(void *tx_queue, struct rte_mbuf **tx_pkts,
>> +		uint16_t nb_pkts);
>> +
>>  /*
>>   * The VIRTIO_NET_F_GUEST_TSO[46] features permit the host to send us
>>   * frames larger than 1514 bytes. We do not yet support software LRO
>> diff --git a/drivers/net/virtio/virtio_rxtx_simple.c b/drivers/net/virtio/virtio_rxtx_simple.c
>> index ef17562..79b4f7f 100644
>> --- a/drivers/net/virtio/virtio_rxtx_simple.c
>> +++ b/drivers/net/virtio/virtio_rxtx_simple.c
>> @@ -288,6 +288,99 @@ virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
>>  	return nb_pkts_received;
>>  }
>>  
>> +#define VIRTIO_TX_FREE_THRESH 32
>> +#define VIRTIO_TX_MAX_FREE_BUF_SZ 32
>> +#define VIRTIO_TX_FREE_NR 32
>> +/* TODO: vq->tx_free_cnt could mean num of free slots so we could avoid shift */
>> +static inline void
>> +virtio_xmit_cleanup(struct virtqueue *vq)
>> +{
>> +	uint16_t i, desc_idx;
>> +	int nb_free = 0;
>> +	struct rte_mbuf *m, *free[VIRTIO_TX_MAX_FREE_BUF_SZ];
>> +
>> +	desc_idx = (uint16_t)(vq->vq_used_cons_idx &
>> +		((vq->vq_nentries >> 1) - 1));
>> +	free[0] = (struct rte_mbuf *)vq->vq_descx[desc_idx++].cookie;
>> +	nb_free = 1;
>> +
>> +	for (i = 1; i < VIRTIO_TX_FREE_NR; i++) {
>> +		m = (struct rte_mbuf *)vq->vq_descx[desc_idx++].cookie;
>> +		if (likely(m->pool == free[0]->pool))
>> +			free[nb_free++] = m;
>> +		else {
>> +			rte_mempool_put_bulk(free[0]->pool, (void **)free,
>> +				nb_free);
>> +			free[0] = m;
>> +			nb_free = 1;
>> +		}
>> +	}
>> +
>> +	rte_mempool_put_bulk(free[0]->pool, (void **)free, nb_free);
>> +	vq->vq_used_cons_idx += VIRTIO_TX_FREE_NR;
>> +	vq->vq_free_cnt += (VIRTIO_TX_FREE_NR << 1);
>> +}
> I think you need to handle refcount, here is a similar patch
> for ixgbe.
ok, like this:

m = (struct rte_mbuf *)vq->vq_descx[desc_idx++].cookie;
if (likely(m != NULL)) {
    ...

>
> Subject: ixgbe: speed up transmit
>
> Coalesce transmit buffers and put them back into the pool
> in one burst.
>
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
>
> --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> @@ -120,12 +120,16 @@ rte_rxmbuf_alloc(struct rte_mempool *mp)
>   * Check for descriptors with their DD bit set and free mbufs.
>   * Return the total number of buffers freed.
>   */
> +#define TX_FREE_BULK 32
> +
>  static inline int __attribute__((always_inline))
>  ixgbe_tx_free_bufs(struct ixgbe_tx_queue *txq)
>  {
>  	struct ixgbe_tx_entry *txep;
>  	uint32_t status;
> -	int i;
> +	int i, n = 0;
> +	struct rte_mempool *txpool = NULL;
> +	struct rte_mbuf *free_list[TX_FREE_BULK];
>  
>  	/* check DD bit on threshold descriptor */
>  	status = txq->tx_ring[txq->tx_next_dd].wb.status;
> @@ -138,20 +142,26 @@ ixgbe_tx_free_bufs(struct ixgbe_tx_queue
>  	 */
>  	txep = &(txq->sw_ring[txq->tx_next_dd - (txq->tx_rs_thresh - 1)]);
>  
> -	/* free buffers one at a time */
> -	if ((txq->txq_flags & (uint32_t)ETH_TXQ_FLAGS_NOREFCOUNT) != 0) {
> -		for (i = 0; i < txq->tx_rs_thresh; ++i, ++txep) {
> -			txep->mbuf->next = NULL;
> -			rte_mempool_put(txep->mbuf->pool, txep->mbuf);
> -			txep->mbuf = NULL;
> -		}
> -	} else {
> -		for (i = 0; i < txq->tx_rs_thresh; ++i, ++txep) {
> -			rte_pktmbuf_free_seg(txep->mbuf);
> -			txep->mbuf = NULL;
> +	for (i = 0; i < txq->tx_rs_thresh; ++i, ++txep) {
> +		struct rte_mbuf *m;
> +
> +		/* free buffers one at a time */
> +		m = __rte_pktmbuf_prefree_seg(txep->mbuf);
> +		txep->mbuf = NULL;
> +
> +		if (n >= TX_FREE_BULK  ||
check whether m is NULL here.
> +		    (n > 0 && m->pool != txpool)) {
> +			rte_mempool_put_bulk(txpool, (void **)free_list, n);
> +			n = 0;
>  		}
> +
> +		txpool = m->pool;
> +		free_list[n++] = m;
>  	}
>  
> +	if (n > 0)
> +		rte_mempool_put_bulk(txpool, (void **)free_list, n);
> +
>  	/* buffers were freed, update counters */
>  	txq->nb_tx_free = (uint16_t)(txq->nb_tx_free + txq->tx_rs_thresh);
>  	txq->tx_next_dd = (uint16_t)(txq->tx_next_dd + txq->tx_rs_thresh);
>
>