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

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

On 10/23/2015 10:17 AM, Xie, Huawei wrote:
> 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;
Missed a line
  m = __rte_pktmbuf_prefree_seg(m)
> 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);
>>
>>
>