Re: [PATCH bpf-next v2 2/3] virtio-net: support IFF_TX_SKB_NO_LINEAR

Re: [PATCH bpf-next v2 2/3] virtio-net: support IFF_TX_SKB_NO_LINEAR

[Alexander Lobakin]

From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Date: Tue, 19 Jan 2021 17:45:11 +0800

> Virtio net supports the case where the skb linear space is empty, so add
> priv_flags.
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index ba8e637..80d637f 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2972,7 +2972,8 @@ static int virtnet_probe(struct virtio_device *vdev)
>  		return -ENOMEM;
>  
>  	/* Set up network device as normal. */
> -	dev->priv_flags |= IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE;
> +	dev->priv_flags |= IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE |
> +		IFF_TX_SKB_NO_LINEAR;

Please align IFF_TX_SKB_NO_LINEAR to IFF_UNICAST_FLT:

	dev->priv_flags |= IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE |
			   IFF_TX_SKB_NO_LINEAR;

>  	dev->netdev_ops = &virtnet_netdev;
>  	dev->features = NETIF_F_HIGHDMA;

Also, the series you sent is showed up incorrectly on lore.kernel.org
and patchwork.kernel.org. Seems like you used different To and Cc for
its parts.
Please use scripts/get_maintainer.pl to the whole series:

scripts/get_maintainer.pl ../patch-build-skb-by-page/*

And use one list of addresses for every message, so they wouldn't
lost.

Al

[PATCH net-next v2 2/3] virtio-net: support IFF_TX_SKB_NO_LINEAR

[Xuan Zhuo]

Virtio net supports the case where the skb linear space is empty, so add
priv_flags.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 drivers/net/virtio_net.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ba8e637..f2ff6c3 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2972,7 +2972,8 @@ static int virtnet_probe(struct virtio_device *vdev)
 		return -ENOMEM;
 
 	/* Set up network device as normal. */
-	dev->priv_flags |= IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE;
+	dev->priv_flags |= IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE |
+			   IFF_TX_SKB_NO_LINEAR;
 	dev->netdev_ops = &virtnet_netdev;
 	dev->features = NETIF_F_HIGHDMA;
 
-- 
1.8.3.1

Re: [PATCH net-next v2 2/3] virtio-net: support IFF_TX_SKB_NO_LINEAR

[Michael S. Tsirkin]

On Wed, Jan 20, 2021 at 03:49:10PM +0800, Xuan Zhuo wrote:
> Virtio net supports the case where the skb linear space is empty, so add
> priv_flags.
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  drivers/net/virtio_net.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index ba8e637..f2ff6c3 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2972,7 +2972,8 @@ static int virtnet_probe(struct virtio_device *vdev)
>  		return -ENOMEM;
>  
>  	/* Set up network device as normal. */
> -	dev->priv_flags |= IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE;
> +	dev->priv_flags |= IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE |
> +			   IFF_TX_SKB_NO_LINEAR;
>  	dev->netdev_ops = &virtnet_netdev;
>  	dev->features = NETIF_F_HIGHDMA;
>  
> -- 
> 1.8.3.1

[PATCH net-next v2 3/3] xsk: build skb by page

[Xuan Zhuo]

This patch is used to construct skb based on page to save memory copy
overhead.

This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the
network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to
directly construct skb. If this feature is not supported, it is still
necessary to copy data to construct skb.

---------------- Performance Testing ------------

The test environment is Aliyun ECS server.
Test cmd:
```
xdpsock -i eth0 -t  -S -s <msg size>
```

Test result data:

size    64      512     1024    1500
copy    1916747 1775988 1600203 1440054
page    1974058 1953655 1945463 1904478
percent 3.0%    10.0%   21.58%  32.3%

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
---
 net/xdp/xsk.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 86 insertions(+), 18 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 8037b04..817a3a5 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -430,6 +430,87 @@ static void xsk_destruct_skb(struct sk_buff *skb)
 	sock_wfree(skb);
 }
 
+static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
+					      struct xdp_desc *desc)
+{
+	u32 len, offset, copy, copied;
+	struct sk_buff *skb;
+	struct page *page;
+	char *buffer;
+	int err, i;
+	u64 addr;
+
+	skb = sock_alloc_send_skb(&xs->sk, 0, 1, &err);
+	if (unlikely(!skb))
+		return ERR_PTR(err);
+
+	addr = desc->addr;
+	len = desc->len;
+
+	buffer = xsk_buff_raw_get_data(xs->pool, addr);
+	offset = offset_in_page(buffer);
+	addr = buffer - (char *)xs->pool->addrs;
+
+	for (copied = 0, i = 0; copied < len; i++) {
+		page = xs->pool->umem->pgs[addr >> PAGE_SHIFT];
+
+		get_page(page);
+
+		copy = min_t(u32, PAGE_SIZE - offset, len - copied);
+
+		skb_fill_page_desc(skb, i, page, offset, copy);
+
+		copied += copy;
+		addr += copy;
+		offset = 0;
+	}
+
+	skb->len += len;
+	skb->data_len += len;
+	skb->truesize += len;
+
+	refcount_add(len, &xs->sk.sk_wmem_alloc);
+
+	return skb;
+}
+
+static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
+				     struct xdp_desc *desc)
+{
+	struct sk_buff *skb = NULL;
+
+	if (xs->dev->priv_flags & IFF_TX_SKB_NO_LINEAR) {
+		skb = xsk_build_skb_zerocopy(xs, desc);
+		if (IS_ERR(skb))
+			return skb;
+	} else {
+		char *buffer;
+		u32 len;
+		int err;
+
+		len = desc->len;
+		skb = sock_alloc_send_skb(&xs->sk, len, 1, &err);
+		if (unlikely(!skb))
+			return ERR_PTR(err);
+
+		skb_put(skb, len);
+		buffer = xsk_buff_raw_get_data(xs->pool, desc->addr);
+		err = skb_store_bits(skb, 0, buffer, len);
+		if (unlikely(err)) {
+			kfree_skb(skb);
+			return ERR_PTR(err);
+		}
+	}
+
+	skb->dev = xs->dev;
+	skb->priority = xs->sk.sk_priority;
+	skb->mark = xs->sk.sk_mark;
+	skb_shinfo(skb)->destructor_arg = (void *)(long)desc->addr;
+	skb->destructor = xsk_destruct_skb;
+
+	return skb;
+}
+
 static int xsk_generic_xmit(struct sock *sk)
 {
 	struct xdp_sock *xs = xdp_sk(sk);
@@ -446,43 +527,30 @@ static int xsk_generic_xmit(struct sock *sk)
 		goto out;
 
 	while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) {
-		char *buffer;
-		u64 addr;
-		u32 len;
-
 		if (max_batch-- == 0) {
 			err = -EAGAIN;
 			goto out;
 		}
 
-		len = desc.len;
-		skb = sock_alloc_send_skb(sk, len, 1, &err);
-		if (unlikely(!skb))
+		skb = xsk_build_skb(xs, &desc);
+		if (IS_ERR(skb)) {
+			err = PTR_ERR(skb);
 			goto out;
+		}
 
-		skb_put(skb, len);
-		addr = desc.addr;
-		buffer = xsk_buff_raw_get_data(xs->pool, addr);
-		err = skb_store_bits(skb, 0, buffer, len);
 		/* This is the backpressure mechanism for the Tx path.
 		 * Reserve space in the completion queue and only proceed
 		 * if there is space in it. This avoids having to implement
 		 * any buffering in the Tx path.
 		 */
 		spin_lock_irqsave(&xs->pool->cq_lock, flags);
-		if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) {
+		if (xskq_prod_reserve(xs->pool->cq)) {
 			spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
 			kfree_skb(skb);
 			goto out;
 		}
 		spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
 
-		skb->dev = xs->dev;
-		skb->priority = sk->sk_priority;
-		skb->mark = sk->sk_mark;
-		skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr;
-		skb->destructor = xsk_destruct_skb;
-
 		err = __dev_direct_xmit(skb, xs->queue_id);
 		if  (err == NETDEV_TX_BUSY) {
 			/* Tell user-space to retry the send */
-- 
1.8.3.1

Re: [PATCH net-next v2 3/3] xsk: build skb by page

[Michael S. Tsirkin]

On Wed, Jan 20, 2021 at 03:50:01PM +0800, Xuan Zhuo wrote:
> This patch is used to construct skb based on page to save memory copy
> overhead.
> 
> This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the
> network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to
> directly construct skb. If this feature is not supported, it is still
> necessary to copy data to construct skb.
> 
> ---------------- Performance Testing ------------
> 
> The test environment is Aliyun ECS server.
> Test cmd:
> ```
> xdpsock -i eth0 -t  -S -s <msg size>
> ```
> 
> Test result data:
> 
> size    64      512     1024    1500
> copy    1916747 1775988 1600203 1440054
> page    1974058 1953655 1945463 1904478
> percent 3.0%    10.0%   21.58%  32.3%
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> Reviewed-by: Dust Li <dust.li@linux.alibaba.com>

I can't see the cover letter or 1/3 in this series - was probably
threaded incorrectly?


> ---
>  net/xdp/xsk.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 86 insertions(+), 18 deletions(-)
> 
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 8037b04..817a3a5 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -430,6 +430,87 @@ static void xsk_destruct_skb(struct sk_buff *skb)
>  	sock_wfree(skb);
>  }
>  
> +static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
> +					      struct xdp_desc *desc)
> +{
> +	u32 len, offset, copy, copied;
> +	struct sk_buff *skb;
> +	struct page *page;
> +	char *buffer;

Actually, make this void *, this way you will not need
casts down the road. I know this is from xsk_generic_xmit -
I don't know why it's char * there, either.

> +	int err, i;
> +	u64 addr;
> +
> +	skb = sock_alloc_send_skb(&xs->sk, 0, 1, &err);
> +	if (unlikely(!skb))
> +		return ERR_PTR(err);
> +
> +	addr = desc->addr;
> +	len = desc->len;
> +
> +	buffer = xsk_buff_raw_get_data(xs->pool, addr);
> +	offset = offset_in_page(buffer);
> +	addr = buffer - (char *)xs->pool->addrs;
> +
> +	for (copied = 0, i = 0; copied < len; i++) {
> +		page = xs->pool->umem->pgs[addr >> PAGE_SHIFT];
> +
> +		get_page(page);
> +
> +		copy = min_t(u32, PAGE_SIZE - offset, len - copied);
> +
> +		skb_fill_page_desc(skb, i, page, offset, copy);
> +
> +		copied += copy;
> +		addr += copy;
> +		offset = 0;
> +	}
> +
> +	skb->len += len;
> +	skb->data_len += len;
> +	skb->truesize += len;
> +
> +	refcount_add(len, &xs->sk.sk_wmem_alloc);
> +
> +	return skb;
> +}
> +
> +static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
> +				     struct xdp_desc *desc)
> +{
> +	struct sk_buff *skb = NULL;
> +
> +	if (xs->dev->priv_flags & IFF_TX_SKB_NO_LINEAR) {
> +		skb = xsk_build_skb_zerocopy(xs, desc);
> +		if (IS_ERR(skb))
> +			return skb;
> +	} else {
> +		char *buffer;
> +		u32 len;
> +		int err;
> +
> +		len = desc->len;
> +		skb = sock_alloc_send_skb(&xs->sk, len, 1, &err);
> +		if (unlikely(!skb))
> +			return ERR_PTR(err);
> +
> +		skb_put(skb, len);
> +		buffer = xsk_buff_raw_get_data(xs->pool, desc->addr);
> +		err = skb_store_bits(skb, 0, buffer, len);
> +		if (unlikely(err)) {
> +			kfree_skb(skb);
> +			return ERR_PTR(err);
> +		}
> +	}
> +
> +	skb->dev = xs->dev;
> +	skb->priority = xs->sk.sk_priority;
> +	skb->mark = xs->sk.sk_mark;
> +	skb_shinfo(skb)->destructor_arg = (void *)(long)desc->addr;
> +	skb->destructor = xsk_destruct_skb;
> +
> +	return skb;
> +}
> +
>  static int xsk_generic_xmit(struct sock *sk)
>  {
>  	struct xdp_sock *xs = xdp_sk(sk);
> @@ -446,43 +527,30 @@ static int xsk_generic_xmit(struct sock *sk)
>  		goto out;
>  
>  	while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) {
> -		char *buffer;
> -		u64 addr;
> -		u32 len;
> -
>  		if (max_batch-- == 0) {
>  			err = -EAGAIN;
>  			goto out;
>  		}
>  
> -		len = desc.len;
> -		skb = sock_alloc_send_skb(sk, len, 1, &err);
> -		if (unlikely(!skb))
> +		skb = xsk_build_skb(xs, &desc);
> +		if (IS_ERR(skb)) {
> +			err = PTR_ERR(skb);
>  			goto out;
> +		}
>  
> -		skb_put(skb, len);
> -		addr = desc.addr;
> -		buffer = xsk_buff_raw_get_data(xs->pool, addr);
> -		err = skb_store_bits(skb, 0, buffer, len);
>  		/* This is the backpressure mechanism for the Tx path.
>  		 * Reserve space in the completion queue and only proceed
>  		 * if there is space in it. This avoids having to implement
>  		 * any buffering in the Tx path.
>  		 */
>  		spin_lock_irqsave(&xs->pool->cq_lock, flags);
> -		if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) {
> +		if (xskq_prod_reserve(xs->pool->cq)) {
>  			spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
>  			kfree_skb(skb);
>  			goto out;
>  		}
>  		spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
>  
> -		skb->dev = xs->dev;
> -		skb->priority = sk->sk_priority;
> -		skb->mark = sk->sk_mark;
> -		skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr;
> -		skb->destructor = xsk_destruct_skb;
> -
>  		err = __dev_direct_xmit(skb, xs->queue_id);
>  		if  (err == NETDEV_TX_BUSY) {
>  			/* Tell user-space to retry the send */
> -- 
> 1.8.3.1

Re: [PATCH net-next v2 3/3] xsk: build skb by page

[Michael S. Tsirkin]

On Wed, Jan 20, 2021 at 03:11:04AM -0500, Michael S. Tsirkin wrote:
> On Wed, Jan 20, 2021 at 03:50:01PM +0800, Xuan Zhuo wrote:
> > This patch is used to construct skb based on page to save memory copy
> > overhead.
> > 
> > This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the
> > network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to
> > directly construct skb. If this feature is not supported, it is still
> > necessary to copy data to construct skb.
> > 
> > ---------------- Performance Testing ------------
> > 
> > The test environment is Aliyun ECS server.
> > Test cmd:
> > ```
> > xdpsock -i eth0 -t  -S -s <msg size>
> > ```
> > 
> > Test result data:
> > 
> > size    64      512     1024    1500
> > copy    1916747 1775988 1600203 1440054
> > page    1974058 1953655 1945463 1904478
> > percent 3.0%    10.0%   21.58%  32.3%
> > 
> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
> 
> I can't see the cover letter or 1/3 in this series - was probably
> threaded incorrectly?


Hmm looked again and now I do see them. My mistake pls ignore.

> 
> > ---
> >  net/xdp/xsk.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++----------
> >  1 file changed, 86 insertions(+), 18 deletions(-)
> > 
> > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> > index 8037b04..817a3a5 100644
> > --- a/net/xdp/xsk.c
> > +++ b/net/xdp/xsk.c
> > @@ -430,6 +430,87 @@ static void xsk_destruct_skb(struct sk_buff *skb)
> >  	sock_wfree(skb);
> >  }
> >  
> > +static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
> > +					      struct xdp_desc *desc)
> > +{
> > +	u32 len, offset, copy, copied;
> > +	struct sk_buff *skb;
> > +	struct page *page;
> > +	char *buffer;
> 
> Actually, make this void *, this way you will not need
> casts down the road. I know this is from xsk_generic_xmit -
> I don't know why it's char * there, either.
> 
> > +	int err, i;
> > +	u64 addr;
> > +
> > +	skb = sock_alloc_send_skb(&xs->sk, 0, 1, &err);
> > +	if (unlikely(!skb))
> > +		return ERR_PTR(err);
> > +
> > +	addr = desc->addr;
> > +	len = desc->len;
> > +
> > +	buffer = xsk_buff_raw_get_data(xs->pool, addr);
> > +	offset = offset_in_page(buffer);
> > +	addr = buffer - (char *)xs->pool->addrs;
> > +
> > +	for (copied = 0, i = 0; copied < len; i++) {
> > +		page = xs->pool->umem->pgs[addr >> PAGE_SHIFT];
> > +
> > +		get_page(page);
> > +
> > +		copy = min_t(u32, PAGE_SIZE - offset, len - copied);
> > +
> > +		skb_fill_page_desc(skb, i, page, offset, copy);
> > +
> > +		copied += copy;
> > +		addr += copy;
> > +		offset = 0;
> > +	}
> > +
> > +	skb->len += len;
> > +	skb->data_len += len;
> > +	skb->truesize += len;
> > +
> > +	refcount_add(len, &xs->sk.sk_wmem_alloc);
> > +
> > +	return skb;
> > +}
> > +
> > +static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
> > +				     struct xdp_desc *desc)
> > +{
> > +	struct sk_buff *skb = NULL;
> > +
> > +	if (xs->dev->priv_flags & IFF_TX_SKB_NO_LINEAR) {
> > +		skb = xsk_build_skb_zerocopy(xs, desc);
> > +		if (IS_ERR(skb))
> > +			return skb;
> > +	} else {
> > +		char *buffer;
> > +		u32 len;
> > +		int err;
> > +
> > +		len = desc->len;
> > +		skb = sock_alloc_send_skb(&xs->sk, len, 1, &err);
> > +		if (unlikely(!skb))
> > +			return ERR_PTR(err);
> > +
> > +		skb_put(skb, len);
> > +		buffer = xsk_buff_raw_get_data(xs->pool, desc->addr);
> > +		err = skb_store_bits(skb, 0, buffer, len);
> > +		if (unlikely(err)) {
> > +			kfree_skb(skb);
> > +			return ERR_PTR(err);
> > +		}
> > +	}
> > +
> > +	skb->dev = xs->dev;
> > +	skb->priority = xs->sk.sk_priority;
> > +	skb->mark = xs->sk.sk_mark;
> > +	skb_shinfo(skb)->destructor_arg = (void *)(long)desc->addr;
> > +	skb->destructor = xsk_destruct_skb;
> > +
> > +	return skb;
> > +}
> > +
> >  static int xsk_generic_xmit(struct sock *sk)
> >  {
> >  	struct xdp_sock *xs = xdp_sk(sk);
> > @@ -446,43 +527,30 @@ static int xsk_generic_xmit(struct sock *sk)
> >  		goto out;
> >  
> >  	while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) {
> > -		char *buffer;
> > -		u64 addr;
> > -		u32 len;
> > -
> >  		if (max_batch-- == 0) {
> >  			err = -EAGAIN;
> >  			goto out;
> >  		}
> >  
> > -		len = desc.len;
> > -		skb = sock_alloc_send_skb(sk, len, 1, &err);
> > -		if (unlikely(!skb))
> > +		skb = xsk_build_skb(xs, &desc);
> > +		if (IS_ERR(skb)) {
> > +			err = PTR_ERR(skb);
> >  			goto out;
> > +		}
> >  
> > -		skb_put(skb, len);
> > -		addr = desc.addr;
> > -		buffer = xsk_buff_raw_get_data(xs->pool, addr);
> > -		err = skb_store_bits(skb, 0, buffer, len);
> >  		/* This is the backpressure mechanism for the Tx path.
> >  		 * Reserve space in the completion queue and only proceed
> >  		 * if there is space in it. This avoids having to implement
> >  		 * any buffering in the Tx path.
> >  		 */
> >  		spin_lock_irqsave(&xs->pool->cq_lock, flags);
> > -		if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) {
> > +		if (xskq_prod_reserve(xs->pool->cq)) {
> >  			spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
> >  			kfree_skb(skb);
> >  			goto out;
> >  		}
> >  		spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
> >  
> > -		skb->dev = xs->dev;
> > -		skb->priority = sk->sk_priority;
> > -		skb->mark = sk->sk_mark;
> > -		skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr;
> > -		skb->destructor = xsk_destruct_skb;
> > -
> >  		err = __dev_direct_xmit(skb, xs->queue_id);
> >  		if  (err == NETDEV_TX_BUSY) {
> >  			/* Tell user-space to retry the send */
> > -- 
> > 1.8.3.1

[PATCH net-next v2 3/3] xsk: build skb by page

[Xuan Zhuo]

This patch is used to construct skb based on page to save memory copy
overhead.

This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the
network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to
directly construct skb. If this feature is not supported, it is still
necessary to copy data to construct skb.

---------------- Performance Testing ------------

The test environment is Aliyun ECS server.
Test cmd:
```
xdpsock -i eth0 -t  -S -s <msg size>
```

Test result data:

size    64      512     1024    1500
copy    1916747 1775988 1600203 1440054
page    1974058 1953655 1945463 1904478
percent 3.0%    10.0%   21.58%  32.3%

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
---
 net/xdp/xsk.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 86 insertions(+), 18 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 8037b04..40bac11 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -430,6 +430,87 @@ static void xsk_destruct_skb(struct sk_buff *skb)
 	sock_wfree(skb);
 }
 
+static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
+					      struct xdp_desc *desc)
+{
+	u32 len, offset, copy, copied;
+	struct sk_buff *skb;
+	struct page *page;
+	void *buffer;
+	int err, i;
+	u64 addr;
+
+	skb = sock_alloc_send_skb(&xs->sk, 0, 1, &err);
+	if (unlikely(!skb))
+		return ERR_PTR(err);
+
+	addr = desc->addr;
+	len = desc->len;
+
+	buffer = xsk_buff_raw_get_data(xs->pool, addr);
+	offset = offset_in_page(buffer);
+	addr = buffer - xs->pool->addrs;
+
+	for (copied = 0, i = 0; copied < len; i++) {
+		page = xs->pool->umem->pgs[addr >> PAGE_SHIFT];
+
+		get_page(page);
+
+		copy = min_t(u32, PAGE_SIZE - offset, len - copied);
+
+		skb_fill_page_desc(skb, i, page, offset, copy);
+
+		copied += copy;
+		addr += copy;
+		offset = 0;
+	}
+
+	skb->len += len;
+	skb->data_len += len;
+	skb->truesize += len;
+
+	refcount_add(len, &xs->sk.sk_wmem_alloc);
+
+	return skb;
+}
+
+static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
+				     struct xdp_desc *desc)
+{
+	struct sk_buff *skb = NULL;
+
+	if (xs->dev->priv_flags & IFF_TX_SKB_NO_LINEAR) {
+		skb = xsk_build_skb_zerocopy(xs, desc);
+		if (IS_ERR(skb))
+			return skb;
+	} else {
+		void *buffer;
+		u32 len;
+		int err;
+
+		len = desc->len;
+		skb = sock_alloc_send_skb(&xs->sk, len, 1, &err);
+		if (unlikely(!skb))
+			return ERR_PTR(err);
+
+		skb_put(skb, len);
+		buffer = xsk_buff_raw_get_data(xs->pool, desc->addr);
+		err = skb_store_bits(skb, 0, buffer, len);
+		if (unlikely(err)) {
+			kfree_skb(skb);
+			return ERR_PTR(err);
+		}
+	}
+
+	skb->dev = xs->dev;
+	skb->priority = xs->sk.sk_priority;
+	skb->mark = xs->sk.sk_mark;
+	skb_shinfo(skb)->destructor_arg = (void *)(long)desc->addr;
+	skb->destructor = xsk_destruct_skb;
+
+	return skb;
+}
+
 static int xsk_generic_xmit(struct sock *sk)
 {
 	struct xdp_sock *xs = xdp_sk(sk);
@@ -446,43 +527,30 @@ static int xsk_generic_xmit(struct sock *sk)
 		goto out;
 
 	while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) {
-		char *buffer;
-		u64 addr;
-		u32 len;
-
 		if (max_batch-- == 0) {
 			err = -EAGAIN;
 			goto out;
 		}
 
-		len = desc.len;
-		skb = sock_alloc_send_skb(sk, len, 1, &err);
-		if (unlikely(!skb))
+		skb = xsk_build_skb(xs, &desc);
+		if (IS_ERR(skb)) {
+			err = PTR_ERR(skb);
 			goto out;
+		}
 
-		skb_put(skb, len);
-		addr = desc.addr;
-		buffer = xsk_buff_raw_get_data(xs->pool, addr);
-		err = skb_store_bits(skb, 0, buffer, len);
 		/* This is the backpressure mechanism for the Tx path.
 		 * Reserve space in the completion queue and only proceed
 		 * if there is space in it. This avoids having to implement
 		 * any buffering in the Tx path.
 		 */
 		spin_lock_irqsave(&xs->pool->cq_lock, flags);
-		if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) {
+		if (xskq_prod_reserve(xs->pool->cq)) {
 			spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
 			kfree_skb(skb);
 			goto out;
 		}
 		spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
 
-		skb->dev = xs->dev;
-		skb->priority = sk->sk_priority;
-		skb->mark = sk->sk_mark;
-		skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr;
-		skb->destructor = xsk_destruct_skb;
-
 		err = __dev_direct_xmit(skb, xs->queue_id);
 		if  (err == NETDEV_TX_BUSY) {
 			/* Tell user-space to retry the send */
-- 
1.8.3.1

Re: [PATCH net-next v2 3/3] xsk: build skb by page

[Alexander Lobakin]

From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Date: Wed, 20 Jan 2021 16:30:56 +0800

> This patch is used to construct skb based on page to save memory copy
> overhead.
> 
> This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the
> network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to
> directly construct skb. If this feature is not supported, it is still
> necessary to copy data to construct skb.
> 
> ---------------- Performance Testing ------------
> 
> The test environment is Aliyun ECS server.
> Test cmd:
> ```
> xdpsock -i eth0 -t  -S -s <msg size>
> ```
> 
> Test result data:
> 
> size    64      512     1024    1500
> copy    1916747 1775988 1600203 1440054
> page    1974058 1953655 1945463 1904478
> percent 3.0%    10.0%   21.58%  32.3%
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
> ---
>  net/xdp/xsk.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 86 insertions(+), 18 deletions(-)

Now I like the result, thanks!

But Patchwork still display your series incorrectly (messages 0 and 1
are missing). I'm concerning maintainers may not take this in such
form. Try to pass the folder's name, not folder/*.patch to
git send-email when sending, and don't use --in-reply-to when sending
a new iteration.

> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 8037b04..40bac11 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -430,6 +430,87 @@ static void xsk_destruct_skb(struct sk_buff *skb)
>  	sock_wfree(skb);
>  }
> 
> +static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
> +					      struct xdp_desc *desc)
> +{
> +	u32 len, offset, copy, copied;
> +	struct sk_buff *skb;
> +	struct page *page;
> +	void *buffer;
> +	int err, i;
> +	u64 addr;
> +
> +	skb = sock_alloc_send_skb(&xs->sk, 0, 1, &err);
> +	if (unlikely(!skb))
> +		return ERR_PTR(err);
> +
> +	addr = desc->addr;
> +	len = desc->len;
> +
> +	buffer = xsk_buff_raw_get_data(xs->pool, addr);
> +	offset = offset_in_page(buffer);
> +	addr = buffer - xs->pool->addrs;
> +
> +	for (copied = 0, i = 0; copied < len; i++) {
> +		page = xs->pool->umem->pgs[addr >> PAGE_SHIFT];
> +
> +		get_page(page);
> +
> +		copy = min_t(u32, PAGE_SIZE - offset, len - copied);
> +
> +		skb_fill_page_desc(skb, i, page, offset, copy);
> +
> +		copied += copy;
> +		addr += copy;
> +		offset = 0;
> +	}
> +
> +	skb->len += len;
> +	skb->data_len += len;
> +	skb->truesize += len;
> +
> +	refcount_add(len, &xs->sk.sk_wmem_alloc);
> +
> +	return skb;
> +}
> +
> +static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
> +				     struct xdp_desc *desc)
> +{
> +	struct sk_buff *skb = NULL;
> +
> +	if (xs->dev->priv_flags & IFF_TX_SKB_NO_LINEAR) {
> +		skb = xsk_build_skb_zerocopy(xs, desc);
> +		if (IS_ERR(skb))
> +			return skb;
> +	} else {
> +		void *buffer;
> +		u32 len;
> +		int err;
> +
> +		len = desc->len;
> +		skb = sock_alloc_send_skb(&xs->sk, len, 1, &err);
> +		if (unlikely(!skb))
> +			return ERR_PTR(err);
> +
> +		skb_put(skb, len);
> +		buffer = xsk_buff_raw_get_data(xs->pool, desc->addr);
> +		err = skb_store_bits(skb, 0, buffer, len);
> +		if (unlikely(err)) {
> +			kfree_skb(skb);
> +			return ERR_PTR(err);
> +		}
> +	}
> +
> +	skb->dev = xs->dev;
> +	skb->priority = xs->sk.sk_priority;
> +	skb->mark = xs->sk.sk_mark;
> +	skb_shinfo(skb)->destructor_arg = (void *)(long)desc->addr;
> +	skb->destructor = xsk_destruct_skb;
> +
> +	return skb;
> +}
> +
>  static int xsk_generic_xmit(struct sock *sk)
>  {
>  	struct xdp_sock *xs = xdp_sk(sk);
> @@ -446,43 +527,30 @@ static int xsk_generic_xmit(struct sock *sk)
>  		goto out;
> 
>  	while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) {
> -		char *buffer;
> -		u64 addr;
> -		u32 len;
> -
>  		if (max_batch-- == 0) {
>  			err = -EAGAIN;
>  			goto out;
>  		}
> 
> -		len = desc.len;
> -		skb = sock_alloc_send_skb(sk, len, 1, &err);
> -		if (unlikely(!skb))
> +		skb = xsk_build_skb(xs, &desc);
> +		if (IS_ERR(skb)) {
> +			err = PTR_ERR(skb);
>  			goto out;
> +		}
> 
> -		skb_put(skb, len);
> -		addr = desc.addr;
> -		buffer = xsk_buff_raw_get_data(xs->pool, addr);
> -		err = skb_store_bits(skb, 0, buffer, len);
>  		/* This is the backpressure mechanism for the Tx path.
>  		 * Reserve space in the completion queue and only proceed
>  		 * if there is space in it. This avoids having to implement
>  		 * any buffering in the Tx path.
>  		 */
>  		spin_lock_irqsave(&xs->pool->cq_lock, flags);
> -		if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) {
> +		if (xskq_prod_reserve(xs->pool->cq)) {
>  			spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
>  			kfree_skb(skb);
>  			goto out;
>  		}
>  		spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
> 
> -		skb->dev = xs->dev;
> -		skb->priority = sk->sk_priority;
> -		skb->mark = sk->sk_mark;
> -		skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr;
> -		skb->destructor = xsk_destruct_skb;
> -
>  		err = __dev_direct_xmit(skb, xs->queue_id);
>  		if  (err == NETDEV_TX_BUSY) {
>  			/* Tell user-space to retry the send */
> --
> 1.8.3.1

Al

Re: [PATCH net-next v2 3/3] xsk: build skb by page

[Magnus Karlsson]

On Wed, Jan 20, 2021 at 9:29 PM Alexander Lobakin <alobakin@pm.me> wrote:
>
> From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> Date: Wed, 20 Jan 2021 16:30:56 +0800
>
> > This patch is used to construct skb based on page to save memory copy
> > overhead.
> >
> > This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the
> > network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to
> > directly construct skb. If this feature is not supported, it is still
> > necessary to copy data to construct skb.
> >
> > ---------------- Performance Testing ------------
> >
> > The test environment is Aliyun ECS server.
> > Test cmd:
> > ```
> > xdpsock -i eth0 -t  -S -s <msg size>
> > ```
> >
> > Test result data:
> >
> > size    64      512     1024    1500
> > copy    1916747 1775988 1600203 1440054
> > page    1974058 1953655 1945463 1904478
> > percent 3.0%    10.0%   21.58%  32.3%
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
> > ---
> >  net/xdp/xsk.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++----------
> >  1 file changed, 86 insertions(+), 18 deletions(-)
>
> Now I like the result, thanks!
>
> But Patchwork still display your series incorrectly (messages 0 and 1
> are missing). I'm concerning maintainers may not take this in such
> form. Try to pass the folder's name, not folder/*.patch to
> git send-email when sending, and don't use --in-reply-to when sending
> a new iteration.

Xuan,

Please make the new submission of the patch set a v3 even though you
did not change the code. Just so we can clearly see it is the new
submission.

> > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> > index 8037b04..40bac11 100644
> > --- a/net/xdp/xsk.c
> > +++ b/net/xdp/xsk.c
> > @@ -430,6 +430,87 @@ static void xsk_destruct_skb(struct sk_buff *skb)
> >       sock_wfree(skb);
> >  }
> >
> > +static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
> > +                                           struct xdp_desc *desc)
> > +{
> > +     u32 len, offset, copy, copied;
> > +     struct sk_buff *skb;
> > +     struct page *page;
> > +     void *buffer;
> > +     int err, i;
> > +     u64 addr;
> > +
> > +     skb = sock_alloc_send_skb(&xs->sk, 0, 1, &err);
> > +     if (unlikely(!skb))
> > +             return ERR_PTR(err);
> > +
> > +     addr = desc->addr;
> > +     len = desc->len;
> > +
> > +     buffer = xsk_buff_raw_get_data(xs->pool, addr);
> > +     offset = offset_in_page(buffer);
> > +     addr = buffer - xs->pool->addrs;
> > +
> > +     for (copied = 0, i = 0; copied < len; i++) {
> > +             page = xs->pool->umem->pgs[addr >> PAGE_SHIFT];
> > +
> > +             get_page(page);
> > +
> > +             copy = min_t(u32, PAGE_SIZE - offset, len - copied);
> > +
> > +             skb_fill_page_desc(skb, i, page, offset, copy);
> > +
> > +             copied += copy;
> > +             addr += copy;
> > +             offset = 0;
> > +     }
> > +
> > +     skb->len += len;
> > +     skb->data_len += len;
> > +     skb->truesize += len;
> > +
> > +     refcount_add(len, &xs->sk.sk_wmem_alloc);
> > +
> > +     return skb;
> > +}
> > +
> > +static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
> > +                                  struct xdp_desc *desc)
> > +{
> > +     struct sk_buff *skb = NULL;
> > +
> > +     if (xs->dev->priv_flags & IFF_TX_SKB_NO_LINEAR) {
> > +             skb = xsk_build_skb_zerocopy(xs, desc);
> > +             if (IS_ERR(skb))
> > +                     return skb;
> > +     } else {
> > +             void *buffer;
> > +             u32 len;
> > +             int err;
> > +
> > +             len = desc->len;
> > +             skb = sock_alloc_send_skb(&xs->sk, len, 1, &err);
> > +             if (unlikely(!skb))
> > +                     return ERR_PTR(err);
> > +
> > +             skb_put(skb, len);
> > +             buffer = xsk_buff_raw_get_data(xs->pool, desc->addr);
> > +             err = skb_store_bits(skb, 0, buffer, len);
> > +             if (unlikely(err)) {
> > +                     kfree_skb(skb);
> > +                     return ERR_PTR(err);
> > +             }
> > +     }
> > +
> > +     skb->dev = xs->dev;
> > +     skb->priority = xs->sk.sk_priority;
> > +     skb->mark = xs->sk.sk_mark;
> > +     skb_shinfo(skb)->destructor_arg = (void *)(long)desc->addr;
> > +     skb->destructor = xsk_destruct_skb;
> > +
> > +     return skb;
> > +}
> > +
> >  static int xsk_generic_xmit(struct sock *sk)
> >  {
> >       struct xdp_sock *xs = xdp_sk(sk);
> > @@ -446,43 +527,30 @@ static int xsk_generic_xmit(struct sock *sk)
> >               goto out;
> >
> >       while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) {
> > -             char *buffer;
> > -             u64 addr;
> > -             u32 len;
> > -
> >               if (max_batch-- == 0) {
> >                       err = -EAGAIN;
> >                       goto out;
> >               }
> >
> > -             len = desc.len;
> > -             skb = sock_alloc_send_skb(sk, len, 1, &err);
> > -             if (unlikely(!skb))
> > +             skb = xsk_build_skb(xs, &desc);
> > +             if (IS_ERR(skb)) {
> > +                     err = PTR_ERR(skb);
> >                       goto out;
> > +             }
> >
> > -             skb_put(skb, len);
> > -             addr = desc.addr;
> > -             buffer = xsk_buff_raw_get_data(xs->pool, addr);
> > -             err = skb_store_bits(skb, 0, buffer, len);
> >               /* This is the backpressure mechanism for the Tx path.
> >                * Reserve space in the completion queue and only proceed
> >                * if there is space in it. This avoids having to implement
> >                * any buffering in the Tx path.
> >                */
> >               spin_lock_irqsave(&xs->pool->cq_lock, flags);
> > -             if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) {
> > +             if (xskq_prod_reserve(xs->pool->cq)) {
> >                       spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
> >                       kfree_skb(skb);
> >                       goto out;
> >               }
> >               spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
> >
> > -             skb->dev = xs->dev;
> > -             skb->priority = sk->sk_priority;
> > -             skb->mark = sk->sk_mark;
> > -             skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr;
> > -             skb->destructor = xsk_destruct_skb;
> > -
> >               err = __dev_direct_xmit(skb, xs->queue_id);
> >               if  (err == NETDEV_TX_BUSY) {
> >                       /* Tell user-space to retry the send */
> > --
> > 1.8.3.1
>
> Al
>

Re: [PATCH net-next v2 3/3] xsk: build skb by page

[Yunsheng Lin]

On 2021/1/21 15:41, Magnus Karlsson wrote:
> On Wed, Jan 20, 2021 at 9:29 PM Alexander Lobakin <alobakin@pm.me> wrote:
>>
>> From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
>> Date: Wed, 20 Jan 2021 16:30:56 +0800
>>
>>> This patch is used to construct skb based on page to save memory copy
>>> overhead.
>>>
>>> This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the
>>> network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to
>>> directly construct skb. If this feature is not supported, it is still
>>> necessary to copy data to construct skb.
>>>
>>> ---------------- Performance Testing ------------
>>>
>>> The test environment is Aliyun ECS server.
>>> Test cmd:
>>> ```
>>> xdpsock -i eth0 -t  -S -s <msg size>
>>> ```
>>>
>>> Test result data:
>>>
>>> size    64      512     1024    1500
>>> copy    1916747 1775988 1600203 1440054
>>> page    1974058 1953655 1945463 1904478
>>> percent 3.0%    10.0%   21.58%  32.3%
>>>
>>> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
>>> Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
>>> ---
>>>  net/xdp/xsk.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++----------
>>>  1 file changed, 86 insertions(+), 18 deletions(-)
>>
>> Now I like the result, thanks!
>>
>> But Patchwork still display your series incorrectly (messages 0 and 1
>> are missing). I'm concerning maintainers may not take this in such
>> form. Try to pass the folder's name, not folder/*.patch to
>> git send-email when sending, and don't use --in-reply-to when sending
>> a new iteration.
> 
> Xuan,
> 
> Please make the new submission of the patch set a v3 even though you
> did not change the code. Just so we can clearly see it is the new
> submission.
> 
>>> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
>>> index 8037b04..40bac11 100644
>>> --- a/net/xdp/xsk.c
>>> +++ b/net/xdp/xsk.c
>>> @@ -430,6 +430,87 @@ static void xsk_destruct_skb(struct sk_buff *skb)
>>>       sock_wfree(skb);
>>>  }
>>>
>>> +static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
>>> +                                           struct xdp_desc *desc)
>>> +{
>>> +     u32 len, offset, copy, copied;
>>> +     struct sk_buff *skb;
>>> +     struct page *page;
>>> +     void *buffer;
>>> +     int err, i;
>>> +     u64 addr;
>>> +
>>> +     skb = sock_alloc_send_skb(&xs->sk, 0, 1, &err);
>>> +     if (unlikely(!skb))
>>> +             return ERR_PTR(err);
>>> +
>>> +     addr = desc->addr;
>>> +     len = desc->len;
>>> +
>>> +     buffer = xsk_buff_raw_get_data(xs->pool, addr);
>>> +     offset = offset_in_page(buffer);
>>> +     addr = buffer - xs->pool->addrs;
>>> +
>>> +     for (copied = 0, i = 0; copied < len; i++) {
>>> +             page = xs->pool->umem->pgs[addr >> PAGE_SHIFT];
>>> +
>>> +             get_page(page);
>>> +
>>> +             copy = min_t(u32, PAGE_SIZE - offset, len - copied);
>>> +
>>> +             skb_fill_page_desc(skb, i, page, offset, copy);
>>> +
>>> +             copied += copy;
>>> +             addr += copy;
>>> +             offset = 0;
>>> +     }
>>> +
>>> +     skb->len += len;
>>> +     skb->data_len += len;
>>> +     skb->truesize += len;
>>> +
>>> +     refcount_add(len, &xs->sk.sk_wmem_alloc);
>>> +
>>> +     return skb;
>>> +}
>>> +
>>> +static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
>>> +                                  struct xdp_desc *desc)
>>> +{
>>> +     struct sk_buff *skb = NULL;

It seems the above init is unnecessary, for the skb is always
set before being used.

>>> +
>>> +     if (xs->dev->priv_flags & IFF_TX_SKB_NO_LINEAR) {
>>> +             skb = xsk_build_skb_zerocopy(xs, desc);
>>> +             if (IS_ERR(skb))
>>> +                     return skb;
>>> +     } else {
>>> +             void *buffer;
>>> +             u32 len;
>>> +             int err;
>>> +
>>> +             len = desc->len;
>>> +             skb = sock_alloc_send_skb(&xs->sk, len, 1, &err);
>>> +             if (unlikely(!skb))
>>> +                     return ERR_PTR(err);
>>> +
>>> +             skb_put(skb, len);
>>> +             buffer = xsk_buff_raw_get_data(xs->pool, desc->addr);
>>> +             err = skb_store_bits(skb, 0, buffer, len);
>>> +             if (unlikely(err)) {
>>> +                     kfree_skb(skb);
>>> +                     return ERR_PTR(err);
>>> +             }
>>> +     }
>>> +
>>> +     skb->dev = xs->dev;
>>> +     skb->priority = xs->sk.sk_priority;
>>> +     skb->mark = xs->sk.sk_mark;
>>> +     skb_shinfo(skb)->destructor_arg = (void *)(long)desc->addr;
>>> +     skb->destructor = xsk_destruct_skb;
>>> +
>>> +     return skb;
>>> +}
>>> +
>>>  static int xsk_generic_xmit(struct sock *sk)
>>>  {
>>>       struct xdp_sock *xs = xdp_sk(sk);
>>> @@ -446,43 +527,30 @@ static int xsk_generic_xmit(struct sock *sk)
>>>               goto out;
>>>
>>>       while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) {
>>> -             char *buffer;
>>> -             u64 addr;
>>> -             u32 len;
>>> -
>>>               if (max_batch-- == 0) {
>>>                       err = -EAGAIN;
>>>                       goto out;
>>>               }
>>>
>>> -             len = desc.len;
>>> -             skb = sock_alloc_send_skb(sk, len, 1, &err);
>>> -             if (unlikely(!skb))
>>> +             skb = xsk_build_skb(xs, &desc);
>>> +             if (IS_ERR(skb)) {
>>> +                     err = PTR_ERR(skb);
>>>                       goto out;
>>> +             }
>>>
>>> -             skb_put(skb, len);
>>> -             addr = desc.addr;
>>> -             buffer = xsk_buff_raw_get_data(xs->pool, addr);
>>> -             err = skb_store_bits(skb, 0, buffer, len);
>>>               /* This is the backpressure mechanism for the Tx path.
>>>                * Reserve space in the completion queue and only proceed
>>>                * if there is space in it. This avoids having to implement
>>>                * any buffering in the Tx path.
>>>                */
>>>               spin_lock_irqsave(&xs->pool->cq_lock, flags);
>>> -             if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) {
>>> +             if (xskq_prod_reserve(xs->pool->cq)) {
>>>                       spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
>>>                       kfree_skb(skb);
>>>                       goto out;
>>>               }
>>>               spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
>>>
>>> -             skb->dev = xs->dev;
>>> -             skb->priority = sk->sk_priority;
>>> -             skb->mark = sk->sk_mark;
>>> -             skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr;
>>> -             skb->destructor = xsk_destruct_skb;
>>> -
>>>               err = __dev_direct_xmit(skb, xs->queue_id);
>>>               if  (err == NETDEV_TX_BUSY) {
>>>                       /* Tell user-space to retry the send */
>>> --
>>> 1.8.3.1
>>
>> Al
>>
> 
> .
> 

Re: [PATCH bpf-next v2 3/3] xsk: build skb by page

[Alexander Lobakin]

From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Date: Tue, 19 Jan 2021 17:45:12 +0800

> This patch is used to construct skb based on page to save memory copy
> overhead.
> 
> This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the
> network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to
> directly construct skb. If this feature is not supported, it is still
> necessary to copy data to construct skb.
> 
> ---------------- Performance Testing ------------
> 
> The test environment is Aliyun ECS server.
> Test cmd:
> ```
> xdpsock -i eth0 -t  -S -s <msg size>
> ```
> 
> Test result data:
> 
> size    64      512     1024    1500
> copy    1916747 1775988 1600203 1440054
> page    1974058 1953655 1945463 1904478
> percent 3.0%    10.0%   21.58%  32.3%
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
> ---
>  net/xdp/xsk.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 94 insertions(+), 18 deletions(-)
> 
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 8037b04..8c291f8 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -430,6 +430,95 @@ static void xsk_destruct_skb(struct sk_buff *skb)
>  	sock_wfree(skb);
>  }
>  
> +static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
> +					      struct xdp_desc *desc)
> +{
> +	u32 len, offset, copy, copied;
> +	struct sk_buff *skb;
> +	struct page *page;
> +	char *buffer;
> +	int err = 0, i;
> +	u64 addr;
> +
> +	skb = sock_alloc_send_skb(&xs->sk, 0, 1, &err);
> +	if (unlikely(!skb))
> +		return NULL;

You can propagate err from here to the outer function:

	if (unlikely(!skb))
		return ERR_PTR(err);

> +	addr = desc->addr;
> +	len = desc->len;
> +
> +	buffer = xsk_buff_raw_get_data(xs->pool, addr);
> +	offset = offset_in_page(buffer);
> +	addr = buffer - (char *)xs->pool->addrs;
> +
> +	for (copied = 0, i = 0; copied < len; ++i) {

i++ would be less confusing here. You build skb frags from frag 0
anyway.

> +		page = xs->pool->umem->pgs[addr >> PAGE_SHIFT];
> +
> +		get_page(page);
> +
> +		copy = min((u32)(PAGE_SIZE - offset), len - copied);

It's better to use min_t(u32, ...) instead of manual casting.

> +
> +		skb_fill_page_desc(skb, i, page, offset, copy);
> +
> +		copied += copy;
> +		addr += copy;
> +		offset = 0;
> +	}
> +
> +	skb->len += len;
> +	skb->data_len += len;
> +	skb->truesize += len;
> +
> +	refcount_add(len, &xs->sk.sk_wmem_alloc);
> +
> +	return skb;
> +}
> +
> +static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
> +				     struct xdp_desc *desc)
> +{
> +	struct sk_buff *skb = NULL;
> +	int err = -ENOMEM;
> +
> +	if (xs->dev->priv_flags & IFF_TX_SKB_NO_LINEAR) {
> +		skb = xsk_build_skb_zerocopy(xs, desc);
> +		if (unlikely(!skb))
> +			goto err;

1. You should'n use goto err here, as skb == NULL, so kfree_skb(skb)
   is redundant.
2. If you would use ERR_PTR() in xsk_build_skb_zerocopy(),
   the condition should look like:

		if (IS_ERR(skb))
			return PTR_ERR(skb);

> +	} else {
> +		char *buffer;
> +		u64 addr;
> +		u32 len;
> +		int err;
> +
> +		len = desc->len;
> +		skb = sock_alloc_send_skb(&xs->sk, len, 1, &err);
> +		if (unlikely(!skb))
> +			goto err;

Same here, if skb == NULL, just return without calling kfree_skb().

> +		skb_put(skb, len);
> +		addr = desc->addr;
> +		buffer = xsk_buff_raw_get_data(xs->pool, desc->addr);
> +		err = skb_store_bits(skb, 0, buffer, len);
> +
> +		if (unlikely(err)) {
> +			err = -EINVAL;

You already have errno in err, no need to override it.

> +			goto err;
> +		}
> +	}
> +
> +	skb->dev = xs->dev;
> +	skb->priority = xs->sk.sk_priority;
> +	skb->mark = xs->sk.sk_mark;
> +	skb_shinfo(skb)->destructor_arg = (void *)(long)desc->addr;
> +	skb->destructor = xsk_destruct_skb;
> +
> +	return skb;
> +
> +err:
> +	kfree_skb(skb);
> +	return ERR_PTR(err);
> +}
> +
>  static int xsk_generic_xmit(struct sock *sk)
>  {
>  	struct xdp_sock *xs = xdp_sk(sk);
> @@ -446,43 +535,30 @@ static int xsk_generic_xmit(struct sock *sk)
>  		goto out;
>  
>  	while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) {
> -		char *buffer;
> -		u64 addr;
> -		u32 len;
> -
>  		if (max_batch-- == 0) {
>  			err = -EAGAIN;
>  			goto out;
>  		}
>  
> -		len = desc.len;
> -		skb = sock_alloc_send_skb(sk, len, 1, &err);
> -		if (unlikely(!skb))
> +		skb = xsk_build_skb(xs, &desc);
> +		if (IS_ERR(skb)) {
> +			err = PTR_ERR(skb);
>  			goto out;
> +		}
>  
> -		skb_put(skb, len);
> -		addr = desc.addr;
> -		buffer = xsk_buff_raw_get_data(xs->pool, addr);
> -		err = skb_store_bits(skb, 0, buffer, len);
>  		/* This is the backpressure mechanism for the Tx path.
>  		 * Reserve space in the completion queue and only proceed
>  		 * if there is space in it. This avoids having to implement
>  		 * any buffering in the Tx path.
>  		 */
>  		spin_lock_irqsave(&xs->pool->cq_lock, flags);
> -		if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) {
> +		if (xskq_prod_reserve(xs->pool->cq)) {
>  			spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
>  			kfree_skb(skb);
>  			goto out;
>  		}
>  		spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
>  
> -		skb->dev = xs->dev;
> -		skb->priority = sk->sk_priority;
> -		skb->mark = sk->sk_mark;
> -		skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr;
> -		skb->destructor = xsk_destruct_skb;
> -
>  		err = __dev_direct_xmit(skb, xs->queue_id);
>  		if  (err == NETDEV_TX_BUSY) {
>  			/* Tell user-space to retry the send */

So please recheck the code and then retest it, especially error
paths (you can inject errors manually here to ensure they work).

Thanks,
Al