diff mbox

[dpdk-dev,v4] virtio: Fix vring entry number issue

Message ID 1413302634-848-1-git-send-email-changchun.ouyang@intel.com (mailing list archive)
State Superseded, archived
Headers show

Commit Message

Ouyang Changchun Oct. 14, 2014, 4:03 p.m. UTC
Fix one issue in virtio TX: it needs one more vring descriptor to hold the virtio
  header when transmitting packets, it is used later to determine whether to free
  more entries from used vring.
  It fixes failing to transmit any packet with 1 segment in the circumstance of only
  1 descriptor in the vring free list.

Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
Reviewed-by: Olivier Matz <olivier.matz@6wind.com>
---
-V4 change:
  Relocate those changelog and annotation here.

-V3 change:
  Resolve compilation issue due to mbuf re-structure.

-V2 change:
  Refine description, 'vring descriptor' is more accurate than 'vring entry';
  Accordingly update test condition (it needs one more descriptor for virtio header) to
  put packets to transmit queue.

-V1 change:
  Fix the vring descriptor issue in virtio TX, it needs one more vring descriptor to hold the
  virtio header.

 lib/librte_pmd_virtio/virtio_rxtx.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

Comments

Huawei Xie Oct. 14, 2014, 4:26 p.m. UTC | #1
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Ouyang Changchun
> Sent: Tuesday, October 14, 2014 9:04 AM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH v4] virtio: Fix vring entry number issue
> 
>   Fix one issue in virtio TX: it needs one more vring descriptor to hold the virtio
>   header when transmitting packets, it is used later to determine whether to free
>   more entries from used vring.
>   It fixes failing to transmit any packet with 1 segment in the circumstance of
> only
>   1 descriptor in the vring free list.
> 
> Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
> Reviewed-by: Olivier Matz <olivier.matz@6wind.com>
> ---
> -V4 change:
>   Relocate those changelog and annotation here.
> 
> -V3 change:
>   Resolve compilation issue due to mbuf re-structure.
> 
> -V2 change:
>   Refine description, 'vring descriptor' is more accurate than 'vring entry';
>   Accordingly update test condition (it needs one more descriptor for virtio
> header) to
>   put packets to transmit queue.
> 
> -V1 change:
>   Fix the vring descriptor issue in virtio TX, it needs one more vring descriptor to
> hold the
>   virtio header.
> 
>  lib/librte_pmd_virtio/virtio_rxtx.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/librte_pmd_virtio/virtio_rxtx.c
> b/lib/librte_pmd_virtio/virtio_rxtx.c
> index 0b10108..ac44c65 100644
> --- a/lib/librte_pmd_virtio/virtio_rxtx.c
> +++ b/lib/librte_pmd_virtio/virtio_rxtx.c
> @@ -699,7 +699,8 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf
> **tx_pkts, uint16_t nb_pkts)
>  	num = (uint16_t)(likely(nb_used < VIRTIO_MBUF_BURST_SZ) ? nb_used :
> VIRTIO_MBUF_BURST_SZ);
> 
>  	while (nb_tx < nb_pkts) {
> -		int need = tx_pkts[nb_tx]->pkt.nb_segs - txvq->vq_free_cnt;
> +		/* Need one more descriptor for virtio header. */
> +		int need = tx_pkts[nb_tx]->nb_segs - txvq->vq_free_cnt + 1;
>  		int deq_cnt = RTE_MIN(need, (int)num);
> 
>  		num -= (deq_cnt > 0) ? deq_cnt : 0;
> @@ -708,7 +709,12 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf
> **tx_pkts, uint16_t nb_pkts)
>  			deq_cnt--;
>  		}
> 
> -		if (tx_pkts[nb_tx]->pkt.nb_segs <= txvq->vq_free_cnt) {
> +		need = (int)tx_pkts[nb_tx]->nb_segs - txvq->vq_free_cnt + 1;
> +		/*
> +		 * Zero or negative value indicates it has enough free
> +		 * decriptors to transmit.
> +		 */
> +		if (need <= 0) {
Could we put a branch hint to favor the fast path?
>  			txm = tx_pkts[nb_tx];
>  			/* Enqueue Packet buffers */
>  			error = virtqueue_enqueue_xmit(txvq, txm);
> --
> 1.8.4.2
Ouyang Changchun Oct. 15, 2014, 3:14 a.m. UTC | #2
Hi Huawei,
I have v5 patch for this comment.
Thanks,
Changchun

> -----Original Message-----
> From: Xie, Huawei
> Sent: Wednesday, October 15, 2014 12:26 AM
> To: Ouyang, Changchun; dev@dpdk.org
> Subject: RE: [dpdk-dev] [PATCH v4] virtio: Fix vring entry number issue
> 
> 
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Ouyang
> Changchun
> > Sent: Tuesday, October 14, 2014 9:04 AM
> > To: dev@dpdk.org
> > Subject: [dpdk-dev] [PATCH v4] virtio: Fix vring entry number issue
> >
> >   Fix one issue in virtio TX: it needs one more vring descriptor to hold the
> virtio
> >   header when transmitting packets, it is used later to determine whether
> to free
> >   more entries from used vring.
> >   It fixes failing to transmit any packet with 1 segment in the
> > circumstance of only
> >   1 descriptor in the vring free list.
> >
> > Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
> > Reviewed-by: Olivier Matz <olivier.matz@6wind.com>
> > ---
> > -V4 change:
> >   Relocate those changelog and annotation here.
> >
> > -V3 change:
> >   Resolve compilation issue due to mbuf re-structure.
> >
> > -V2 change:
> >   Refine description, 'vring descriptor' is more accurate than 'vring entry';
> >   Accordingly update test condition (it needs one more descriptor for
> > virtio
> > header) to
> >   put packets to transmit queue.
> >
> > -V1 change:
> >   Fix the vring descriptor issue in virtio TX, it needs one more vring
> > descriptor to hold the
> >   virtio header.
> >
> >  lib/librte_pmd_virtio/virtio_rxtx.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/librte_pmd_virtio/virtio_rxtx.c
> > b/lib/librte_pmd_virtio/virtio_rxtx.c
> > index 0b10108..ac44c65 100644
> > --- a/lib/librte_pmd_virtio/virtio_rxtx.c
> > +++ b/lib/librte_pmd_virtio/virtio_rxtx.c
> > @@ -699,7 +699,8 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf
> > **tx_pkts, uint16_t nb_pkts)
> >  	num = (uint16_t)(likely(nb_used < VIRTIO_MBUF_BURST_SZ) ?
> nb_used :
> > VIRTIO_MBUF_BURST_SZ);
> >
> >  	while (nb_tx < nb_pkts) {
> > -		int need = tx_pkts[nb_tx]->pkt.nb_segs - txvq->vq_free_cnt;
> > +		/* Need one more descriptor for virtio header. */
> > +		int need = tx_pkts[nb_tx]->nb_segs - txvq->vq_free_cnt + 1;
> >  		int deq_cnt = RTE_MIN(need, (int)num);
> >
> >  		num -= (deq_cnt > 0) ? deq_cnt : 0; @@ -708,7 +709,12 @@
> > virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t
> > nb_pkts)
> >  			deq_cnt--;
> >  		}
> >
> > -		if (tx_pkts[nb_tx]->pkt.nb_segs <= txvq->vq_free_cnt) {
> > +		need = (int)tx_pkts[nb_tx]->nb_segs - txvq->vq_free_cnt +
> 1;
> > +		/*
> > +		 * Zero or negative value indicates it has enough free
> > +		 * decriptors to transmit.
> > +		 */
> > +		if (need <= 0) {
> Could we put a branch hint to favor the fast path?
> >  			txm = tx_pkts[nb_tx];
> >  			/* Enqueue Packet buffers */
> >  			error = virtqueue_enqueue_xmit(txvq, txm);
> > --
> > 1.8.4.2
diff mbox

Patch

diff --git a/lib/librte_pmd_virtio/virtio_rxtx.c b/lib/librte_pmd_virtio/virtio_rxtx.c
index 0b10108..ac44c65 100644
--- a/lib/librte_pmd_virtio/virtio_rxtx.c
+++ b/lib/librte_pmd_virtio/virtio_rxtx.c
@@ -699,7 +699,8 @@  virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 	num = (uint16_t)(likely(nb_used < VIRTIO_MBUF_BURST_SZ) ? nb_used : VIRTIO_MBUF_BURST_SZ);
 
 	while (nb_tx < nb_pkts) {
-		int need = tx_pkts[nb_tx]->pkt.nb_segs - txvq->vq_free_cnt;
+		/* Need one more descriptor for virtio header. */
+		int need = tx_pkts[nb_tx]->nb_segs - txvq->vq_free_cnt + 1;
 		int deq_cnt = RTE_MIN(need, (int)num);
 
 		num -= (deq_cnt > 0) ? deq_cnt : 0;
@@ -708,7 +709,12 @@  virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 			deq_cnt--;
 		}
 
-		if (tx_pkts[nb_tx]->pkt.nb_segs <= txvq->vq_free_cnt) {
+		need = (int)tx_pkts[nb_tx]->nb_segs - txvq->vq_free_cnt + 1;
+		/*
+		 * Zero or negative value indicates it has enough free
+		 * decriptors to transmit.
+		 */
+		if (need <= 0) {
 			txm = tx_pkts[nb_tx];
 			/* Enqueue Packet buffers */
 			error = virtqueue_enqueue_xmit(txvq, txm);