[dpdk-dev] [PATCH 04/10] net/virtio: optimize flags update for packed ring

[Tiwei Bie]

Cache the AVAIL, USED and WRITE bits to avoid calculating
them as much as possible. Note that, the WRITE bit isn't
cached for control queue.

Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>
---
 drivers/net/virtio/virtio_ethdev.c | 35 ++++++++++++++----------------
 drivers/net/virtio/virtio_rxtx.c   | 31 ++++++++++----------------
 drivers/net/virtio/virtqueue.h     |  8 +++----
 3 files changed, 32 insertions(+), 42 deletions(-)

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index ff16fb63e..9060b6b33 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -149,7 +149,7 @@ virtio_send_command_packed(struct virtnet_ctl *cvq,
 	int head;
 	struct vring_packed_desc *desc = vq->ring_packed.desc_packed;
 	struct virtio_pmd_ctrl *result;
-	bool avail_wrap_counter;
+	uint16_t flags;
 	int sum = 0;
 	int nb_descs = 0;
 	int k;
@@ -161,14 +161,15 @@ virtio_send_command_packed(struct virtnet_ctl *cvq,
 	 * One RX packet for ACK.
 	 */
 	head = vq->vq_avail_idx;
-	avail_wrap_counter = vq->avail_wrap_counter;
+	flags = vq->cached_flags;
 	desc[head].addr = cvq->virtio_net_hdr_mem;
 	desc[head].len = sizeof(struct virtio_net_ctrl_hdr);
 	vq->vq_free_cnt--;
 	nb_descs++;
 	if (++vq->vq_avail_idx >= vq->vq_nentries) {
 		vq->vq_avail_idx -= vq->vq_nentries;
-		vq->avail_wrap_counter ^= 1;
+		vq->cached_flags ^=
+			VRING_DESC_F_AVAIL(1) | VRING_DESC_F_USED(1);
 	}
 
 	for (k = 0; k < pkt_num; k++) {
@@ -177,34 +178,31 @@ virtio_send_command_packed(struct virtnet_ctl *cvq,
 			+ sizeof(ctrl->status) + sizeof(uint8_t) * sum;
 		desc[vq->vq_avail_idx].len = dlen[k];
 		desc[vq->vq_avail_idx].flags = VRING_DESC_F_NEXT |
-			VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
-			VRING_DESC_F_USED(!vq->avail_wrap_counter);
+			vq->cached_flags;
 		sum += dlen[k];
 		vq->vq_free_cnt--;
 		nb_descs++;
 		if (++vq->vq_avail_idx >= vq->vq_nentries) {
 			vq->vq_avail_idx -= vq->vq_nentries;
-			vq->avail_wrap_counter ^= 1;
+			vq->cached_flags ^=
+				VRING_DESC_F_AVAIL(1) | VRING_DESC_F_USED(1);
 		}
 	}
 
 	desc[vq->vq_avail_idx].addr = cvq->virtio_net_hdr_mem
 		+ sizeof(struct virtio_net_ctrl_hdr);
 	desc[vq->vq_avail_idx].len = sizeof(ctrl->status);
-	desc[vq->vq_avail_idx].flags = VRING_DESC_F_WRITE |
-		VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
-		VRING_DESC_F_USED(!vq->avail_wrap_counter);
+	desc[vq->vq_avail_idx].flags = VRING_DESC_F_WRITE | vq->cached_flags;
 	vq->vq_free_cnt--;
 	nb_descs++;
 	if (++vq->vq_avail_idx >= vq->vq_nentries) {
 		vq->vq_avail_idx -= vq->vq_nentries;
-		vq->avail_wrap_counter ^= 1;
+		vq->cached_flags ^=
+			VRING_DESC_F_AVAIL(1) | VRING_DESC_F_USED(1);
 	}
 
 	virtio_wmb(vq->hw->weak_barriers);
-	desc[head].flags = VRING_DESC_F_NEXT |
-		VRING_DESC_F_AVAIL(avail_wrap_counter) |
-		VRING_DESC_F_USED(!avail_wrap_counter);
+	desc[head].flags = VRING_DESC_F_NEXT | flags;
 
 	virtio_wmb(vq->hw->weak_barriers);
 	virtqueue_notify(vq);
@@ -226,12 +224,12 @@ virtio_send_command_packed(struct virtnet_ctl *cvq,
 	PMD_INIT_LOG(DEBUG, "vq->vq_free_cnt=%d\n"
 			"vq->vq_avail_idx=%d\n"
 			"vq->vq_used_cons_idx=%d\n"
-			"vq->avail_wrap_counter=%d\n"
+			"vq->cached_flags=0x%x\n"
 			"vq->used_wrap_counter=%d\n",
 			vq->vq_free_cnt,
 			vq->vq_avail_idx,
 			vq->vq_used_cons_idx,
-			vq->avail_wrap_counter,
+			vq->cached_flags,
 			vq->used_wrap_counter);
 
 	result = cvq->virtio_net_hdr_mz->addr;
@@ -491,11 +489,10 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t vtpci_queue_idx)
 	vq->vq_nentries = vq_size;
 	vq->event_flags_shadow = 0;
 	if (vtpci_packed_queue(hw)) {
-		vq->avail_wrap_counter = 1;
 		vq->used_wrap_counter = 1;
-		vq->avail_used_flags =
-			VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
-			VRING_DESC_F_USED(!vq->avail_wrap_counter);
+		vq->cached_flags = VRING_DESC_F_AVAIL(1);
+		if (queue_type == VTNET_RQ)
+			vq->cached_flags |= VRING_DESC_F_WRITE;
 	}
 
 	/*
diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index 771d3c3f6..3c354baef 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -431,7 +431,7 @@ virtqueue_enqueue_recv_refill_packed(struct virtqueue *vq,
 				     struct rte_mbuf **cookie, uint16_t num)
 {
 	struct vring_packed_desc *start_dp = vq->ring_packed.desc_packed;
-	uint16_t flags = VRING_DESC_F_WRITE | vq->avail_used_flags;
+	uint16_t flags = vq->cached_flags;
 	struct virtio_hw *hw = vq->hw;
 	struct vq_desc_extra *dxp;
 	uint16_t idx;
@@ -460,11 +460,9 @@ virtqueue_enqueue_recv_refill_packed(struct virtqueue *vq,
 		start_dp[idx].flags = flags;
 		if (++vq->vq_avail_idx >= vq->vq_nentries) {
 			vq->vq_avail_idx -= vq->vq_nentries;
-			vq->avail_wrap_counter ^= 1;
-			vq->avail_used_flags =
-				VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
-				VRING_DESC_F_USED(!vq->avail_wrap_counter);
-			flags = VRING_DESC_F_WRITE | vq->avail_used_flags;
+			vq->cached_flags ^=
+				VRING_DESC_F_AVAIL(1) | VRING_DESC_F_USED(1);
+			flags = vq->cached_flags;
 		}
 	}
 	vq->vq_free_cnt = (uint16_t)(vq->vq_free_cnt - num);
@@ -643,7 +641,7 @@ virtqueue_enqueue_xmit_packed_fast(struct virtnet_tx *txvq,
 	dxp->ndescs = 1;
 	dxp->cookie = cookie;
 
-	flags = vq->avail_used_flags;
+	flags = vq->cached_flags;
 
 	/* prepend cannot fail, checked by caller */
 	hdr = (struct virtio_net_hdr *)
@@ -662,8 +660,7 @@ virtqueue_enqueue_xmit_packed_fast(struct virtnet_tx *txvq,
 
 	if (++vq->vq_avail_idx >= vq->vq_nentries) {
 		vq->vq_avail_idx -= vq->vq_nentries;
-		vq->avail_wrap_counter ^= 1;
-		vq->avail_used_flags ^=
+		vq->cached_flags ^=
 			VRING_DESC_F_AVAIL(1) | VRING_DESC_F_USED(1);
 	}
 
@@ -705,7 +702,7 @@ virtqueue_enqueue_xmit_packed(struct virtnet_tx *txvq, struct rte_mbuf *cookie,
 
 	head_dp = &vq->ring_packed.desc_packed[idx];
 	head_flags = cookie->next ? VRING_DESC_F_NEXT : 0;
-	head_flags |= vq->avail_used_flags;
+	head_flags |= vq->cached_flags;
 
 	if (can_push) {
 		/* prepend cannot fail, checked by caller */
@@ -730,10 +727,8 @@ virtqueue_enqueue_xmit_packed(struct virtnet_tx *txvq, struct rte_mbuf *cookie,
 		idx++;
 		if (idx >= vq->vq_nentries) {
 			idx -= vq->vq_nentries;
-			vq->avail_wrap_counter ^= 1;
-			vq->avail_used_flags =
-				VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
-				VRING_DESC_F_USED(!vq->avail_wrap_counter);
+			vq->cached_flags ^=
+				VRING_DESC_F_AVAIL(1) | VRING_DESC_F_USED(1);
 		}
 	}
 
@@ -746,17 +741,15 @@ virtqueue_enqueue_xmit_packed(struct virtnet_tx *txvq, struct rte_mbuf *cookie,
 		start_dp[idx].len  = cookie->data_len;
 		if (likely(idx != head_idx)) {
 			flags = cookie->next ? VRING_DESC_F_NEXT : 0;
-			flags |= vq->avail_used_flags;
+			flags |= vq->cached_flags;
 			start_dp[idx].flags = flags;
 		}
 		prev = idx;
 		idx++;
 		if (idx >= vq->vq_nentries) {
 			idx -= vq->vq_nentries;
-			vq->avail_wrap_counter ^= 1;
-			vq->avail_used_flags =
-				VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
-				VRING_DESC_F_USED(!vq->avail_wrap_counter);
+			vq->cached_flags ^=
+				VRING_DESC_F_AVAIL(1) | VRING_DESC_F_USED(1);
 		}
 	} while ((cookie = cookie->next) != NULL);
 
diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index 24fa873c3..80c0c43c3 100644
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -193,10 +193,10 @@ struct virtqueue {
 	struct virtio_hw  *hw; /**< virtio_hw structure pointer. */
 	struct vring vq_ring;  /**< vring keeping desc, used and avail */
 	struct vring_packed ring_packed;  /**< vring keeping descs */
-	bool avail_wrap_counter;
 	bool used_wrap_counter;
+	uint16_t cached_flags; /**< cached flags for descs */
 	uint16_t event_flags_shadow;
-	uint16_t avail_used_flags;
+
 	/**
 	 * Last consumed descriptor in the used table,
 	 * trails vq_ring.used->idx.
@@ -478,9 +478,9 @@ virtqueue_notify(struct virtqueue *vq)
 	if (vtpci_packed_queue((vq)->hw)) { \
 		PMD_INIT_LOG(DEBUG, \
 		"VQ: - size=%d; free=%d; used_cons_idx=%d; avail_idx=%d;" \
-		"VQ: - avail_wrap_counter=%d; used_wrap_counter=%d", \
+		" cached_flags=0x%x; used_wrap_counter=%d", \
 		(vq)->vq_nentries, (vq)->vq_free_cnt, (vq)->vq_used_cons_idx, \
-		(vq)->vq_avail_idx, (vq)->avail_wrap_counter, \
+		(vq)->vq_avail_idx, (vq)->cached_flags, \
 		(vq)->used_wrap_counter); \
 		break; \
 	} \
-- 
2.17.1