[dpdk-dev] [PATCH v2] virtio: Fix vring entry number issue

[dpdk-dev] [PATCH v2] virtio: Fix vring entry number issue

[Ouyang Changchun]

-- V1 change:
  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.

-- 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.
 
Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
---
 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..c736362 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]->pkt.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]->pkt.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);
-- 
1.8.4.2

[dpdk-dev] [PATCH v3] virtio: Fix vring entry number issue

[Ouyang Changchun]

-- V1 change:
  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.
 
-- 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.

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

Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
---
 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) {
 			txm = tx_pkts[nb_tx];
 			/* Enqueue Packet buffers */
 			error = virtqueue_enqueue_xmit(txvq, txm);
-- 
1.8.4.2

Re: [dpdk-dev] [PATCH v3] virtio: Fix vring entry number issue

[Ouyang, Changchun]

Hi Olivier,

Any other comments for this v3 patch?

Thanks and regards,
Changchun

> -----Original Message-----
> From: Ouyang, Changchun
> Sent: Tuesday, October 14, 2014 11:13 PM
> To: dev@dpdk.org
> Cc: Cao, Waterman; Ouyang, Changchun
> Subject: [PATCH v3] virtio: Fix vring entry number issue
> 
> -- V1 change:
>   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.
> 
> -- 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.
> 
> -- V3 change:
>   Resolve compilation issue due to mbuf re-structure.
> 
> Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
> ---
>  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) {
>  			txm = tx_pkts[nb_tx];
>  			/* Enqueue Packet buffers */
>  			error = virtqueue_enqueue_xmit(txvq, txm);
> --
> 1.8.4.2

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

[Ouyang Changchun]

  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) {
 			txm = tx_pkts[nb_tx];
 			/* Enqueue Packet buffers */
 			error = virtqueue_enqueue_xmit(txvq, txm);
-- 
1.8.4.2

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

[Xie, Huawei]

> -----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

[dpdk-dev] [PATCH v5] virtio: Fix vring entry number issue

[Ouyang Changchun]

  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>
---

-V5 change:
  Use 'likely' to hint compiler to generate favorable codes.

-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 ad6401c..3f6bad2 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]->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]->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
+		 * descriptors to use for transmitting.
+		 */
+		if (likely(need <= 0)) {
 			txm = tx_pkts[nb_tx];
 			/* Enqueue Packet buffers */
 			error = virtqueue_enqueue_xmit(txvq, txm);
-- 
1.8.4.2

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

[Ouyang, Changchun]

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

Re: [dpdk-dev] [PATCH v5] virtio: Fix vring entry number issue

[Thomas Monjalon]

2014-10-15 11:11, Ouyang Changchun:
>   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>

Applied

Thanks
-- 
Thomas