On Tue, Mar 19, 2019 at 02:43:06PM +0800, Tiwei Bie wrote:
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....@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);

Maybe name it avail_used_flags instead of cached flags. Also we could
use a constant value.
        }

        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;

same here. it's not really cached, it's pre-calculated. And here we
could also use a pre-calculated constand/define.
Otherwise looks good! Did you see any performance improvements?


regards,
Jens

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