From: Stephen Hemminger <stephen@networkplumber.org>
To: "Xie, Huawei" <huawei.xie@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
"changchun.ouyang@intel.com" <changchun.ouyang@intel.com>
Subject: Re: [dpdk-dev] [PATCH 1/5] virtio: clean up space checks on xmit
Date: Mon, 19 Oct 2015 08:48:35 -0700 [thread overview]
Message-ID: <20151019084835.7bbeb2c3@xeon-e3> (raw)
In-Reply-To: <C37D651A908B024F974696C65296B57B4B12B838@SHSMSX101.ccr.corp.intel.com>
On Mon, 19 Oct 2015 08:02:07 +0000
"Xie, Huawei" <huawei.xie@intel.com> wrote:
> 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.
The only case that matters is if virtio_xmit_cleanup can not
free up any slots.
> > 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 15:48 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
2015-10-19 15:48 ` Stephen Hemminger [this message]
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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