[dpdk-dev] [PATCH v3 3/3] net/iavf: enable AVX512 for TX

[Morten Brørup]

> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Wenzhuo Lu
> Sent: Monday, September 21, 2020 10:14 AM
> 
> To enhance the per-core performance, this patch adds some AVX512
> instructions to the data path to handle the TX descriptors.
> 
> Signed-off-by: Wenzhuo Lu <wenzhuo.lu at intel.com>
> Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
> Signed-off-by: Leyi Rong <leyi.rong at intel.com>

[...]

> +static inline void
> +iavf_vtx(volatile struct iavf_tx_desc *txdp,
> +	 struct rte_mbuf **pkt, uint16_t nb_pkts,  uint64_t flags)
> +{
> +	const uint64_t hi_qw_tmpl = (IAVF_TX_DESC_DTYPE_DATA |
> +			((uint64_t)flags  << IAVF_TXD_QW1_CMD_SHIFT));
> +
> +	/* if unaligned on 32-bit boundary, do one to align */
> +	if (((uintptr_t)txdp & 0x1F) != 0 && nb_pkts != 0) {
> +		iavf_vtx1(txdp, *pkt, flags);
> +		nb_pkts--, txdp++, pkt++;
> +	}
> +
> +	/* do two at a time while possible, in bursts */

It looks like four at a time, not two.

> +	for (; nb_pkts > 3; txdp += 4, pkt += 4, nb_pkts -= 4) {
> +		__m512i desc4 =
> +			_mm512_set_epi64
> +				((uint64_t)pkt[3]->data_len,
> +				 pkt[3]->buf_iova,
> +				 (uint64_t)pkt[2]->data_len,
> +				 pkt[2]->buf_iova,
> +				 (uint64_t)pkt[1]->data_len,
> +				 pkt[1]->buf_iova,
> +				 (uint64_t)pkt[0]->data_len,
> +				 pkt[0]->buf_iova);
> +		__m512i hi_qw_tmpl_4 = _mm512_set1_epi64(hi_qw_tmpl);
> +		__m512i data_off_4 =
> +			_mm512_set_epi64
> +				(0,
> +				 pkt[3]->data_off,
> +				 0,
> +				 pkt[2]->data_off,
> +				 0,
> +				 pkt[1]->data_off,
> +				 0,
> +				 pkt[0]->data_off);
> +
> +		desc4 = _mm512_mask_slli_epi64(desc4, IAVF_TX_LEN_MASK,
> desc4,
> +					       IAVF_TXD_QW1_TX_BUF_SZ_SHIFT);
> +		desc4 = _mm512_mask_or_epi64(desc4, IAVF_TX_LEN_MASK,
> desc4,
> +					     hi_qw_tmpl_4);
> +		desc4 = _mm512_mask_add_epi64(desc4, IAVF_TX_OFF_MASK,
> desc4,
> +					      data_off_4);
> +		_mm512_storeu_si512((void *)txdp, desc4);
> +	}
> +
> +	/* do any last ones */
> +	while (nb_pkts) {
> +		iavf_vtx1(txdp, *pkt, flags);
> +		txdp++, pkt++, nb_pkts--;
> +	}
> +}