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vhost: read last used index once

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Instead of calculating the address of a packed descriptor based on the
vq->desc_packed and vq->last_used_idx every time, store that base
address in desc_base. On arm, this saves 176 bytes in code size of
function in which vhost_flush_enqueue_batch_packed gets inlined.

Signed-off-by: Balazs Nemeth <bnemeth@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
This commit is contained in:
Balazs Nemeth 2021-04-28 10:17:31 +08:00 committed by Chenbo Xia
parent 895f409c4a
commit d18db8049c
1 changed files with 8 additions and 5 deletions
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13
lib/vhost/virtio_net.c
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@ -217,6 +217,8 @@ vhost_flush_enqueue_batch_packed(struct virtio_net *dev,
{
uint16_t i;
uint16_t flags;
uint16_t last_used_idx = vq->last_used_idx;
struct vring_packed_desc *desc_base = &vq->desc_packed[last_used_idx];
if (vq->shadow_used_idx) {
do_data_copy_enqueue(dev, vq);
@ -226,16 +228,17 @@ vhost_flush_enqueue_batch_packed(struct virtio_net *dev,
flags = PACKED_DESC_ENQUEUE_USED_FLAG(vq->used_wrap_counter);
vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
vq->desc_packed[vq->last_used_idx + i].id = ids[i];
vq->desc_packed[vq->last_used_idx + i].len = lens[i];
desc_base[i].id = ids[i];
desc_base[i].len = lens[i];
}
rte_atomic_thread_fence(__ATOMIC_RELEASE);
vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE)
vq->desc_packed[vq->last_used_idx + i].flags = flags;
vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
desc_base[i].flags = flags;
}
vhost_log_cache_used_vring(dev, vq, vq->last_used_idx *
vhost_log_cache_used_vring(dev, vq, last_used_idx *
sizeof(struct vring_packed_desc),
sizeof(struct vring_packed_desc) *
PACKED_BATCH_SIZE);