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From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: tiwei.bie@intel.com,
zhihong.wang@intel.com,
dev@dpdk.org
Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
Date: Fri, 6 Jul 2018 09:04:47 +0200
Message-Id: <20180706070449.1946-4-maxime.coquelin@redhat.com>
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References: <20180706070449.1946-1-maxime.coquelin@redhat.com>
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Subject: [dpdk-dev] [PATCH v4 3/5] vhost: improve prefetching in dequeue path
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This is an optimization to prefetch next buffer while the
current one is being processed.
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
lib/librte_vhost/virtio_net.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 6339296c7..2cfd8585c 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -902,7 +902,13 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
buf_iova = buf_vec[vec_idx].buf_iova;
buf_len = buf_vec[vec_idx].buf_len;
- rte_prefetch0((void *)(uintptr_t)buf_addr);
+ /*
+ * Prefecth desc n + 1 buffer while
+ * desc n buffer is processed.
+ */
+ if (vec_idx + 1 < nr_vec)
+ rte_prefetch0((void *)(uintptr_t)
+ buf_vec[vec_idx + 1].buf_addr);
buf_offset = 0;
buf_avail = buf_len;
@@ -1134,6 +1140,8 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
if (likely(dev->dequeue_zero_copy == 0))
update_shadow_used_ring(vq, head_idx, 0);
+ rte_prefetch0((void *)(uintptr_t)buf_vec[0].buf_addr);
+
pkts[i] = rte_pktmbuf_alloc(mbuf_pool);
if (unlikely(pkts[i] == NULL)) {
RTE_LOG(ERR, VHOST_DATA,
--
2.14.4