From: "Xie, Huawei" <huawei.xie@intel.com>
To: Stephen Hemminger <stephen@networkplumber.org>,
"changchun.ouyang@intel.com" <changchun.ouyang@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 1/5] virtio: clean up space checks on xmit
Date: Mon, 19 Oct 2015 08:02:07 +0000 [thread overview]
Message-ID: <C37D651A908B024F974696C65296B57B4B12B838@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <1445231772-17467-2-git-send-email-stephen@networkplumber.org>
On 10/19/2015 1:16 PM, Stephen Hemminger wrote:
> The space check for transmit ring only needs a single conditional.
> I.e only need to recheck for space if there was no space in first check.
I see you reorganized the code. It is more clear and readable with your
change, but no check is removed.
We could remove the check after virtio_xmit_cleanup. In current
implementation, we assume the virtio_xmit_cleanup and vq_ring_free_chain
always succeed.
> This can help performance and simplifies loop.
>
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
> drivers/net/virtio/virtio_rxtx.c | 66 ++++++++++++++++------------------------
> 1 file changed, 27 insertions(+), 39 deletions(-)
>
> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
> index c5b53bb..5b50ed0 100644
> --- a/drivers/net/virtio/virtio_rxtx.c
> +++ b/drivers/net/virtio/virtio_rxtx.c
> @@ -745,7 +745,6 @@ uint16_t
> virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
> {
> struct virtqueue *txvq = tx_queue;
> - struct rte_mbuf *txm;
> uint16_t nb_used, nb_tx;
> int error;
>
> @@ -759,57 +758,46 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
> if (likely(nb_used > txvq->vq_nentries - txvq->vq_free_thresh))
> virtio_xmit_cleanup(txvq, nb_used);
>
> - nb_tx = 0;
> + for (nb_tx = 0; nb_tx < nb_pkts; nb_tx++) {
> + struct rte_mbuf *txm = tx_pkts[nb_tx];
> + int need = txm->nb_segs - txvq->vq_free_cnt + 1;
>
> - while (nb_tx < nb_pkts) {
> - /* Need one more descriptor for virtio header. */
> - int need = tx_pkts[nb_tx]->nb_segs - txvq->vq_free_cnt + 1;
> -
> - /*Positive value indicates it need free vring descriptors */
> + /* Positive value indicates it need free vring descriptors */
As you fix the comment, if it is correct, could you do s/need/needs/ as
well, :)?
> if (unlikely(need > 0)) {
> nb_used = VIRTQUEUE_NUSED(txvq);
> virtio_rmb();
> need = RTE_MIN(need, (int)nb_used);
>
> virtio_xmit_cleanup(txvq, need);
> - need = (int)tx_pkts[nb_tx]->nb_segs -
> - txvq->vq_free_cnt + 1;
> - }
> -
> - /*
> - * Zero or negative value indicates it has enough free
> - * descriptors to use for transmitting.
> - */
> - if (likely(need <= 0)) {
> - txm = tx_pkts[nb_tx];
> -
> - /* Do VLAN tag insertion */
> - if (unlikely(txm->ol_flags & PKT_TX_VLAN_PKT)) {
> - error = rte_vlan_insert(&txm);
> - if (unlikely(error)) {
> - rte_pktmbuf_free(txm);
> - ++nb_tx;
> - continue;
> - }
Still need is rechecked here. It could be removed if virtio_xmit_cleanup
ensures need would be <= 0 after the call.
> + need = txm->nb_segs - txvq->vq_free_cnt + 1;
> + if (unlikely(need > 0)) {
> + PMD_TX_LOG(ERR,
> + "No free tx descriptors to transmit");
> + break;
> }
> + }
>
> - /* Enqueue Packet buffers */
> - error = virtqueue_enqueue_xmit(txvq, txm);
> + /* Do VLAN tag insertion */
> + if (unlikely(txm->ol_flags & PKT_TX_VLAN_PKT)) {
> + error = rte_vlan_insert(&txm);
> if (unlikely(error)) {
> - if (error == ENOSPC)
> - PMD_TX_LOG(ERR, "virtqueue_enqueue Free count = 0");
> - else if (error == EMSGSIZE)
> - PMD_TX_LOG(ERR, "virtqueue_enqueue Free count < 1");
> - else
> - PMD_TX_LOG(ERR, "virtqueue_enqueue error: %d", error);
> - break;
> + rte_pktmbuf_free(txm);
> + continue;
> }
> - nb_tx++;
> - txvq->bytes += txm->pkt_len;
> - } else {
> - PMD_TX_LOG(ERR, "No free tx descriptors to transmit");
> + }
> +
> + /* Enqueue Packet buffers */
> + error = virtqueue_enqueue_xmit(txvq, txm);
> + if (unlikely(error)) {
> + if (error == ENOSPC)
> + PMD_TX_LOG(ERR, "virtqueue_enqueue Free count = 0");
> + else if (error == EMSGSIZE)
> + PMD_TX_LOG(ERR, "virtqueue_enqueue Free count < 1");
> + else
> + PMD_TX_LOG(ERR, "virtqueue_enqueue error: %d", error);
> break;
> }
> + txvq->bytes += txm->pkt_len;
> }
>
> txvq->packets += nb_tx;
next prev parent reply other threads:[~2015-10-19 8:02 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-19 5:16 [dpdk-dev] [PATCH v2 0/5] virtio: Tx performance improvements Stephen Hemminger
2015-10-19 5:16 ` [dpdk-dev] [PATCH 1/5] virtio: clean up space checks on xmit Stephen Hemminger
2015-10-19 8:02 ` Xie, Huawei [this message]
2015-10-19 15:48 ` Stephen Hemminger
2015-10-19 16:27 ` Xie, Huawei
2015-10-19 5:16 ` [dpdk-dev] [PATCH 2/5] virtio: don't use unlikely for normal tx stuff Stephen Hemminger
2015-10-19 5:16 ` [dpdk-dev] [PATCH 3/5] virtio: use indirect ring elements Stephen Hemminger
2015-10-19 13:19 ` Xie, Huawei
2015-10-19 15:47 ` Stephen Hemminger
2015-10-19 16:18 ` Xie, Huawei
2015-10-30 18:01 ` Thomas Monjalon
2015-10-19 5:16 ` [dpdk-dev] [PATCH 4/5] virtio: use any layout on transmit Stephen Hemminger
2015-10-19 16:28 ` Xie, Huawei
2015-10-19 16:43 ` Stephen Hemminger
2015-10-19 16:56 ` Xie, Huawei
2015-10-26 23:47 ` Stephen Hemminger
2015-10-19 17:19 ` Stephen Hemminger
2015-10-19 5:16 ` [dpdk-dev] [PATCH 5/5] virtio: optimize transmit enqueue Stephen Hemminger
2015-10-20 1:48 ` Xie, Huawei
2015-10-21 13:18 ` [dpdk-dev] [PATCH v2 0/5] virtio: Tx performance improvements Thomas Monjalon
2015-10-22 10:38 ` Xie, Huawei
2015-10-22 12:13 ` Xie, Huawei
2015-10-22 16:04 ` Stephen Hemminger
2015-10-23 9:00 ` Xie, Huawei
2015-10-26 23:52 ` Stephen Hemminger
2015-10-27 1:56 ` Xie, Huawei
2015-10-27 2:23 ` Stephen Hemminger
2015-10-27 2:38 ` Xie, Huawei
2015-10-26 14:05 ` Xie, Huawei
2016-01-05 8:10 ` Xie, Huawei
2016-01-06 12:03 ` Thomas Monjalon
2016-01-14 13:49 ` Xie, Huawei
2016-03-04 6:18 ` Xie, Huawei
2016-03-04 18:17 ` Stephen Hemminger
2016-03-08 1:38 ` Xie, Huawei
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