> -----Original Message-----
> From: Maxime Coquelin <maxime.coque...@redhat.com>
> Sent: Tuesday, October 6, 2020 11:00 PM
> To: Liu, Yong <yong....@intel.com>; Xia, Chenbo <chenbo....@intel.com>;
> Wang, Zhihong <zhihong.w...@intel.com>
> Cc: dev@dpdk.org
> Subject: Re: [PATCH v2 5/5] vhost: add packed ring vectorized enqueue
>
>
>
> On 9/21/20 8:48 AM, Marvin Liu wrote:
> > Optimize vhost packed ring enqueue path with SIMD instructions. Four
> > descriptors status and length are batched handled with AVX512
> > instructions. Address translation operations are also accelerated
> > by AVX512 instructions.
> >
> > Signed-off-by: Marvin Liu <yong....@intel.com>
> >
> > diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> > index fc7daf2145..b78b2c5c1b 100644
> > --- a/lib/librte_vhost/vhost.h
> > +++ b/lib/librte_vhost/vhost.h
> > @@ -1132,4 +1132,10 @@ vhost_reserve_avail_batch_packed_avx(struct
> virtio_net *dev,
> > uint16_t avail_idx,
> > uintptr_t *desc_addrs,
> > uint16_t *ids);
> > +
> > +int
> > +virtio_dev_rx_batch_packed_avx(struct virtio_net *dev,
> > + struct vhost_virtqueue *vq,
> > + struct rte_mbuf **pkts);
> > +
> > #endif /* _VHOST_NET_CDEV_H_ */
> > diff --git a/lib/librte_vhost/vhost_vec_avx.c
> b/lib/librte_vhost/vhost_vec_avx.c
> > index dc5322d002..7d2250ed86 100644
> > --- a/lib/librte_vhost/vhost_vec_avx.c
> > +++ b/lib/librte_vhost/vhost_vec_avx.c
> > @@ -35,9 +35,15 @@
> > #define PACKED_AVAIL_FLAG ((0ULL | VRING_DESC_F_AVAIL) <<
> FLAGS_BITS_OFFSET)
> > #define PACKED_AVAIL_FLAG_WRAP ((0ULL | VRING_DESC_F_USED) << \
> > FLAGS_BITS_OFFSET)
> > +#define PACKED_WRITE_AVAIL_FLAG (PACKED_AVAIL_FLAG | \
> > + ((0ULL | VRING_DESC_F_WRITE) << FLAGS_BITS_OFFSET))
> > +#define PACKED_WRITE_AVAIL_FLAG_WRAP
> (PACKED_AVAIL_FLAG_WRAP | \
> > + ((0ULL | VRING_DESC_F_WRITE) << FLAGS_BITS_OFFSET))
> >
> > #define DESC_FLAGS_POS 0xaa
> > #define MBUF_LENS_POS 0x6666
> > +#define DESC_LENS_POS 0x4444
> > +#define DESC_LENS_FLAGS_POS 0xB0B0B0B0
> >
> > int
> > vhost_reserve_avail_batch_packed_avx(struct virtio_net *dev,
> > @@ -179,3 +185,154 @@ vhost_reserve_avail_batch_packed_avx(struct
> virtio_net *dev,
> >
> > return -1;
> > }
> > +
> > +int
> > +virtio_dev_rx_batch_packed_avx(struct virtio_net *dev,
> > + struct vhost_virtqueue *vq,
> > + struct rte_mbuf **pkts)
> > +{
> > + struct vring_packed_desc *descs = vq->desc_packed;
> > + uint16_t avail_idx = vq->last_avail_idx;
> > + uint64_t desc_addrs[PACKED_BATCH_SIZE];
> > + uint32_t buf_offset = dev->vhost_hlen;
> > + uint32_t desc_status;
> > + uint64_t lens[PACKED_BATCH_SIZE];
> > + uint16_t i;
> > + void *desc_addr;
> > + uint8_t cmp_low, cmp_high, cmp_result;
> > +
> > + if (unlikely(avail_idx & PACKED_BATCH_MASK))
> > + return -1;
>
> Same comment as for patch 4. Packed ring size may not be a pow2.
>
Thanks, will fix in next version.
> > + /* check refcnt and nb_segs */
> > + __m256i mbuf_ref = _mm256_set1_epi64x(DEFAULT_REARM_DATA);
> > +
> > + /* load four mbufs rearm data */
> > + __m256i mbufs = _mm256_set_epi64x(
> > + *pkts[3]->rearm_data,
> > + *pkts[2]->rearm_data,
> > + *pkts[1]->rearm_data,
> > + *pkts[0]->rearm_data);
> > +
> > + uint16_t cmp = _mm256_cmpneq_epu16_mask(mbufs, mbuf_ref);
> > + if (cmp & MBUF_LENS_POS)
> > + return -1;
> > +
> > + /* check desc status */
> > + desc_addr = &vq->desc_packed[avail_idx];
> > + __m512i desc_vec = _mm512_loadu_si512(desc_addr);
> > +
> > + __m512i avail_flag_vec;
> > + __m512i used_flag_vec;
> > + if (vq->avail_wrap_counter) {
> > +#if defined(RTE_ARCH_I686)
>
> Is supporting AVX512 on i686 really useful/necessary?
>
It is useless for function point of view. Here is for successful compilation
if enabled i686 build.
> > + avail_flag_vec =
> _mm512_set4_epi64(PACKED_WRITE_AVAIL_FLAG,
> > + 0x0, PACKED_WRITE_AVAIL_FLAG,
> 0x0);
> > + used_flag_vec = _mm512_set4_epi64(PACKED_FLAGS_MASK,
> 0x0,
> > + PACKED_FLAGS_MASK, 0x0);
> > +#else
> > + avail_flag_vec =
> _mm512_maskz_set1_epi64(DESC_FLAGS_POS,
> > + PACKED_WRITE_AVAIL_FLAG);
> > + used_flag_vec =
> _mm512_maskz_set1_epi64(DESC_FLAGS_POS,
> > + PACKED_FLAGS_MASK);
> > +#endif
> > + } else {
> > +#if defined(RTE_ARCH_I686)
> > + avail_flag_vec = _mm512_set4_epi64(
> > + PACKED_WRITE_AVAIL_FLAG_WRAP,
> 0x0,
> > + PACKED_WRITE_AVAIL_FLAG, 0x0);
> > + used_flag_vec = _mm512_set4_epi64(0x0, 0x0, 0x0, 0x0);
> > +#else
> > + avail_flag_vec =
> _mm512_maskz_set1_epi64(DESC_FLAGS_POS,
> > + PACKED_WRITE_AVAIL_FLAG_WRAP);
> > + used_flag_vec = _mm512_setzero_epi32();
> > +#endif
> > + }
> > +
> > + desc_status =
> _mm512_mask_cmp_epu16_mask(BATCH_FLAGS_MASK, desc_vec,
> > + avail_flag_vec, _MM_CMPINT_NE);
> > + if (desc_status)
> > + return -1;
> > +
> > + if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)) {
> > + vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
> > + uint64_t size = (uint64_t)descs[avail_idx + i].len;
> > + desc_addrs[i] = __vhost_iova_to_vva(dev, vq,
> > + descs[avail_idx + i].addr, &size,
> > + VHOST_ACCESS_RW);
> > +
> > + if (!desc_addrs[i])
> > + return -1;
> > +
> > + rte_prefetch0(rte_pktmbuf_mtod_offset(pkts[i], void
> *,
> > + 0));
> > + }
> > + } else {
> > + /* check buffer fit into one region & translate address */
> > + __m512i regions_low_addrs =
> > + _mm512_loadu_si512((void *)&dev-
> >regions_low_addrs);
> > + __m512i regions_high_addrs =
> > + _mm512_loadu_si512((void *)&dev-
> >regions_high_addrs);
> > + vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
> > + uint64_t addr_low = descs[avail_idx + i].addr;
> > + uint64_t addr_high = addr_low +
> > + descs[avail_idx + i].len;
> > + __m512i low_addr_vec =
> _mm512_set1_epi64(addr_low);
> > + __m512i high_addr_vec =
> _mm512_set1_epi64(addr_high);
> > +
> > + cmp_low =
> _mm512_cmp_epi64_mask(low_addr_vec,
> > + regions_low_addrs,
> _MM_CMPINT_NLT);
> > + cmp_high =
> _mm512_cmp_epi64_mask(high_addr_vec,
> > + regions_high_addrs,
> _MM_CMPINT_LT);
> > + cmp_result = cmp_low & cmp_high;
> > + int index = __builtin_ctz(cmp_result);
> > + if (unlikely((uint32_t)index >= dev->mem->nregions))
> > + return -1;
> > +
> > + desc_addrs[i] = addr_low +
> > + dev->mem->regions[index].host_user_addr -
> > + dev->mem->regions[index].guest_phys_addr;
> > + rte_prefetch0(rte_pktmbuf_mtod_offset(pkts[i], void
> *,
> > + 0));
> > + }
> > + }
> > +
> > + /* check length is enough */
> > + __m512i pkt_lens = _mm512_set_epi32(
> > + 0, pkts[3]->pkt_len, 0, 0,
> > + 0, pkts[2]->pkt_len, 0, 0,
> > + 0, pkts[1]->pkt_len, 0, 0,
> > + 0, pkts[0]->pkt_len, 0, 0);
> > +
> > + __m512i mbuf_len_offset =
> _mm512_maskz_set1_epi32(DESC_LENS_POS,
> > + dev->vhost_hlen);
> > + __m512i buf_len_vec = _mm512_add_epi32(pkt_lens,
> mbuf_len_offset);
> > + uint16_t lens_cmp =
> _mm512_mask_cmp_epu32_mask(DESC_LENS_POS,
> > + desc_vec, buf_len_vec, _MM_CMPINT_LT);
> > + if (lens_cmp)
> > + return -1;
> > +
> > + vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
> > + rte_memcpy((void *)(uintptr_t)(desc_addrs[i] + buf_offset),
> > + rte_pktmbuf_mtod_offset(pkts[i], void *, 0),
> > + pkts[i]->pkt_len);
> > + }
> > +
> > + if (unlikely((dev->features & (1ULL << VHOST_F_LOG_ALL)))) {
> > + vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
> > + lens[i] = descs[avail_idx + i].len;
> > + vhost_log_cache_write_iova(dev, vq,
> > + descs[avail_idx + i].addr, lens[i]);
> > + }
> > + }
> > +
> > + vq_inc_last_avail_packed(vq, PACKED_BATCH_SIZE);
> > + vq_inc_last_used_packed(vq, PACKED_BATCH_SIZE);
> > + /* save len and flags, skip addr and id */
> > + __m512i desc_updated = _mm512_mask_add_epi16(desc_vec,
> > + DESC_LENS_FLAGS_POS, buf_len_vec,
> > + used_flag_vec);
> > + _mm512_storeu_si512(desc_addr, desc_updated);
> > +
> > + return 0;
> > +}
> > diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> > index e4d2e2e7d6..5c56a8d6ff 100644
> > --- a/lib/librte_vhost/virtio_net.c
> > +++ b/lib/librte_vhost/virtio_net.c
> > @@ -1354,6 +1354,21 @@ virtio_dev_rx_single_packed(struct virtio_net
> *dev,
> > return 0;
> > }
> >
> > +static __rte_always_inline int
> > +virtio_dev_rx_handle_batch_packed(struct virtio_net *dev,
> > + struct vhost_virtqueue *vq,
> > + struct rte_mbuf **pkts)
> > +
> > +{
> > + if (unlikely(dev->vectorized))
> > +#ifdef CC_AVX512_SUPPORT
> > + return virtio_dev_rx_batch_packed_avx(dev, vq, pkts);
> > +#else
> > + return virtio_dev_rx_batch_packed(dev, vq, pkts);
> > +#endif
> > + return virtio_dev_rx_batch_packed(dev, vq, pkts);
>
> It should be as below to not have any performance impact when
> CC_AVX512_SUPPORT is not set:
>
> #ifdef CC_AVX512_SUPPORT
> if (unlikely(dev->vectorized))
> return virtio_dev_rx_batch_packed_avx(dev, vq, pkts);
> #else
> return virtio_dev_rx_batch_packed(dev, vq, pkts);
> #endif
>
Got, will fix in next version.
> > +}
> > +
> > static __rte_noinline uint32_t
> > virtio_dev_rx_packed(struct virtio_net *dev,
> > struct vhost_virtqueue *__rte_restrict vq,
> > @@ -1367,8 +1382,8 @@ virtio_dev_rx_packed(struct virtio_net *dev,
> > rte_prefetch0(&vq->desc_packed[vq->last_avail_idx]);
> >
> > if (remained >= PACKED_BATCH_SIZE) {
> > - if (!virtio_dev_rx_batch_packed(dev, vq,
> > - &pkts[pkt_idx])) {
> > + if (!virtio_dev_rx_handle_batch_packed(dev, vq,
> > + &pkts[pkt_idx])) {
> > pkt_idx += PACKED_BATCH_SIZE;
> > remained -= PACKED_BATCH_SIZE;
> > continue;
> >
