[PATCH net-next v2] tun: support NAPI for packets received from batched XDP buffs

[PATCH net-next v2] tun: support NAPI for packets received from batched XDP buffs

[Harold Huang]

In tun, NAPI is supported and we can also use NAPI in the path of
batched XDP buffs to accelerate packet processing. What is more, after
we use NAPI, GRO is also supported. The iperf shows that the throughput of
single stream could be improved from 4.5Gbps to 9.2Gbps. Additionally, 9.2
Gbps nearly reachs the line speed of the phy nic and there is still about
15% idle cpu core remaining on the vhost thread.

Test topology:

[iperf server]<--->tap<--->dpdk testpmd<--->phy nic<--->[iperf client]

Iperf stream:

Before:
...
[  5]   5.00-6.00   sec   558 MBytes  4.68 Gbits/sec    0   1.50 MBytes
[  5]   6.00-7.00   sec   556 MBytes  4.67 Gbits/sec    1   1.35 MBytes
[  5]   7.00-8.00   sec   556 MBytes  4.67 Gbits/sec    2   1.18 MBytes
[  5]   8.00-9.00   sec   559 MBytes  4.69 Gbits/sec    0   1.48 MBytes
[  5]   9.00-10.00  sec   556 MBytes  4.67 Gbits/sec    1   1.33 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  5.39 GBytes  4.63 Gbits/sec   72          sender
[  5]   0.00-10.04  sec  5.39 GBytes  4.61 Gbits/sec               receiver

After:
...
[  5]   5.00-6.00   sec  1.07 GBytes  9.19 Gbits/sec    0   1.55 MBytes
[  5]   6.00-7.00   sec  1.08 GBytes  9.30 Gbits/sec    0   1.63 MBytes
[  5]   7.00-8.00   sec  1.08 GBytes  9.25 Gbits/sec    0   1.72 MBytes
[  5]   8.00-9.00   sec  1.08 GBytes  9.25 Gbits/sec   77   1.31 MBytes
[  5]   9.00-10.00  sec  1.08 GBytes  9.24 Gbits/sec    0   1.48 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  10.8 GBytes  9.28 Gbits/sec  166          sender
[  5]   0.00-10.04  sec  10.8 GBytes  9.24 Gbits/sec               receiver
....

Reported-at: https://lore.kernel.org/all/CACGkMEvTLG0Ayg+TtbN4q4pPW-ycgCCs3sC3-TF8cuRTf7Pp1A@mail.gmail.com
Signed-off-by: Harold Huang <baymaxhuang@gmail.com>
---
v1 -> v2
 - fix commit messages
 - add queued flag to avoid void unnecessary napi suggested by Jason

 drivers/net/tun.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index fed85447701a..c7d8b7c821d8 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2379,7 +2379,7 @@ static void tun_put_page(struct tun_page *tpage)
 }
 
 static int tun_xdp_one(struct tun_struct *tun,
-		       struct tun_file *tfile,
+		       struct tun_file *tfile, int *queued,
 		       struct xdp_buff *xdp, int *flush,
 		       struct tun_page *tpage)
 {
@@ -2388,6 +2388,7 @@ static int tun_xdp_one(struct tun_struct *tun,
 	struct virtio_net_hdr *gso = &hdr->gso;
 	struct bpf_prog *xdp_prog;
 	struct sk_buff *skb = NULL;
+	struct sk_buff_head *queue;
 	u32 rxhash = 0, act;
 	int buflen = hdr->buflen;
 	int err = 0;
@@ -2464,7 +2465,15 @@ static int tun_xdp_one(struct tun_struct *tun,
 	    !tfile->detached)
 		rxhash = __skb_get_hash_symmetric(skb);
 
-	netif_receive_skb(skb);
+	if (tfile->napi_enabled) {
+		queue = &tfile->sk.sk_write_queue;
+		spin_lock(&queue->lock);
+		__skb_queue_tail(queue, skb);
+		spin_unlock(&queue->lock);
+		(*queued)++;
+	} else {
+		netif_receive_skb(skb);
+	}
 
 	/* No need to disable preemption here since this function is
 	 * always called with bh disabled
@@ -2492,7 +2501,7 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 	if (ctl && (ctl->type == TUN_MSG_PTR)) {
 		struct tun_page tpage;
 		int n = ctl->num;
-		int flush = 0;
+		int flush = 0, queued = 0;
 
 		memset(&tpage, 0, sizeof(tpage));
 
@@ -2501,12 +2510,15 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 
 		for (i = 0; i < n; i++) {
 			xdp = &((struct xdp_buff *)ctl->ptr)[i];
-			tun_xdp_one(tun, tfile, xdp, &flush, &tpage);
+			tun_xdp_one(tun, tfile, &queued, xdp, &flush, &tpage);
 		}
 
 		if (flush)
 			xdp_do_flush();
 
+		if (tfile->napi_enabled && queued > 0)
+			napi_schedule(&tfile->napi);
+
 		rcu_read_unlock();
 		local_bh_enable();
 
-- 
2.27.0

Re: [PATCH net-next v2] tun: support NAPI for packets received from batched XDP buffs

[Jason Wang]

On Fri, Feb 25, 2022 at 5:03 PM Harold Huang <baymaxhuang@gmail.com> wrote:
>
> In tun, NAPI is supported and we can also use NAPI in the path of
> batched XDP buffs to accelerate packet processing. What is more, after
> we use NAPI, GRO is also supported. The iperf shows that the throughput of
> single stream could be improved from 4.5Gbps to 9.2Gbps. Additionally, 9.2
> Gbps nearly reachs the line speed of the phy nic and there is still about
> 15% idle cpu core remaining on the vhost thread.
>
> Test topology:
>
> [iperf server]<--->tap<--->dpdk testpmd<--->phy nic<--->[iperf client]
>
> Iperf stream:
>
> Before:
> ...
> [  5]   5.00-6.00   sec   558 MBytes  4.68 Gbits/sec    0   1.50 MBytes
> [  5]   6.00-7.00   sec   556 MBytes  4.67 Gbits/sec    1   1.35 MBytes
> [  5]   7.00-8.00   sec   556 MBytes  4.67 Gbits/sec    2   1.18 MBytes
> [  5]   8.00-9.00   sec   559 MBytes  4.69 Gbits/sec    0   1.48 MBytes
> [  5]   9.00-10.00  sec   556 MBytes  4.67 Gbits/sec    1   1.33 MBytes
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-10.00  sec  5.39 GBytes  4.63 Gbits/sec   72          sender
> [  5]   0.00-10.04  sec  5.39 GBytes  4.61 Gbits/sec               receiver
>
> After:
> ...
> [  5]   5.00-6.00   sec  1.07 GBytes  9.19 Gbits/sec    0   1.55 MBytes
> [  5]   6.00-7.00   sec  1.08 GBytes  9.30 Gbits/sec    0   1.63 MBytes
> [  5]   7.00-8.00   sec  1.08 GBytes  9.25 Gbits/sec    0   1.72 MBytes
> [  5]   8.00-9.00   sec  1.08 GBytes  9.25 Gbits/sec   77   1.31 MBytes
> [  5]   9.00-10.00  sec  1.08 GBytes  9.24 Gbits/sec    0   1.48 MBytes
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-10.00  sec  10.8 GBytes  9.28 Gbits/sec  166          sender
> [  5]   0.00-10.04  sec  10.8 GBytes  9.24 Gbits/sec               receiver
> ....
>
> Reported-at: https://lore.kernel.org/all/CACGkMEvTLG0Ayg+TtbN4q4pPW-ycgCCs3sC3-TF8cuRTf7Pp1A@mail.gmail.com
> Signed-off-by: Harold Huang <baymaxhuang@gmail.com>
> ---
> v1 -> v2
>  - fix commit messages
>  - add queued flag to avoid void unnecessary napi suggested by Jason
>
>  drivers/net/tun.c | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index fed85447701a..c7d8b7c821d8 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2379,7 +2379,7 @@ static void tun_put_page(struct tun_page *tpage)
>  }
>
>  static int tun_xdp_one(struct tun_struct *tun,
> -                      struct tun_file *tfile,
> +                      struct tun_file *tfile, int *queued,
>                        struct xdp_buff *xdp, int *flush,
>                        struct tun_page *tpage)

Nit: how about simply returning the number of packets queued here?

Thanks

>  {
> @@ -2388,6 +2388,7 @@ static int tun_xdp_one(struct tun_struct *tun,
>         struct virtio_net_hdr *gso = &hdr->gso;
>         struct bpf_prog *xdp_prog;
>         struct sk_buff *skb = NULL;
> +       struct sk_buff_head *queue;
>         u32 rxhash = 0, act;
>         int buflen = hdr->buflen;
>         int err = 0;
> @@ -2464,7 +2465,15 @@ static int tun_xdp_one(struct tun_struct *tun,
>             !tfile->detached)
>                 rxhash = __skb_get_hash_symmetric(skb);
>
> -       netif_receive_skb(skb);
> +       if (tfile->napi_enabled) {
> +               queue = &tfile->sk.sk_write_queue;
> +               spin_lock(&queue->lock);
> +               __skb_queue_tail(queue, skb);
> +               spin_unlock(&queue->lock);
> +               (*queued)++;
> +       } else {
> +               netif_receive_skb(skb);
> +       }
>
>         /* No need to disable preemption here since this function is
>          * always called with bh disabled
> @@ -2492,7 +2501,7 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
>         if (ctl && (ctl->type == TUN_MSG_PTR)) {
>                 struct tun_page tpage;
>                 int n = ctl->num;
> -               int flush = 0;
> +               int flush = 0, queued = 0;
>
>                 memset(&tpage, 0, sizeof(tpage));
>
> @@ -2501,12 +2510,15 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
>
>                 for (i = 0; i < n; i++) {
>                         xdp = &((struct xdp_buff *)ctl->ptr)[i];
> -                       tun_xdp_one(tun, tfile, xdp, &flush, &tpage);
> +                       tun_xdp_one(tun, tfile, &queued, xdp, &flush, &tpage);
>                 }
>
>                 if (flush)
>                         xdp_do_flush();
>
> +               if (tfile->napi_enabled && queued > 0)
> +                       napi_schedule(&tfile->napi);
> +
>                 rcu_read_unlock();
>                 local_bh_enable();
>
> --
> 2.27.0
>

Re: [PATCH net-next v2] tun: support NAPI for packets received from batched XDP buffs

[Eric Dumazet]

On 2/25/22 01:02, Harold Huang wrote:
> In tun, NAPI is supported and we can also use NAPI in the path of
> batched XDP buffs to accelerate packet processing. What is more, after
> we use NAPI, GRO is also supported. The iperf shows that the throughput of
> single stream could be improved from 4.5Gbps to 9.2Gbps. Additionally, 9.2
> Gbps nearly reachs the line speed of the phy nic and there is still about
> 15% idle cpu core remaining on the vhost thread.
>
> Test topology:
>
> [iperf server]<--->tap<--->dpdk testpmd<--->phy nic<--->[iperf client]
>
> Iperf stream:
>
> Before:
> ...
> [  5]   5.00-6.00   sec   558 MBytes  4.68 Gbits/sec    0   1.50 MBytes
> [  5]   6.00-7.00   sec   556 MBytes  4.67 Gbits/sec    1   1.35 MBytes
> [  5]   7.00-8.00   sec   556 MBytes  4.67 Gbits/sec    2   1.18 MBytes
> [  5]   8.00-9.00   sec   559 MBytes  4.69 Gbits/sec    0   1.48 MBytes
> [  5]   9.00-10.00  sec   556 MBytes  4.67 Gbits/sec    1   1.33 MBytes
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-10.00  sec  5.39 GBytes  4.63 Gbits/sec   72          sender
> [  5]   0.00-10.04  sec  5.39 GBytes  4.61 Gbits/sec               receiver
>
> After:
> ...
> [  5]   5.00-6.00   sec  1.07 GBytes  9.19 Gbits/sec    0   1.55 MBytes
> [  5]   6.00-7.00   sec  1.08 GBytes  9.30 Gbits/sec    0   1.63 MBytes
> [  5]   7.00-8.00   sec  1.08 GBytes  9.25 Gbits/sec    0   1.72 MBytes
> [  5]   8.00-9.00   sec  1.08 GBytes  9.25 Gbits/sec   77   1.31 MBytes
> [  5]   9.00-10.00  sec  1.08 GBytes  9.24 Gbits/sec    0   1.48 MBytes
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-10.00  sec  10.8 GBytes  9.28 Gbits/sec  166          sender
> [  5]   0.00-10.04  sec  10.8 GBytes  9.24 Gbits/sec               receiver
> ....
>
> Reported-at: https://lore.kernel.org/all/CACGkMEvTLG0Ayg+TtbN4q4pPW-ycgCCs3sC3-TF8cuRTf7Pp1A@mail.gmail.com
> Signed-off-by: Harold Huang <baymaxhuang@gmail.com>
> ---
> v1 -> v2
>   - fix commit messages
>   - add queued flag to avoid void unnecessary napi suggested by Jason
>
>   drivers/net/tun.c | 20 ++++++++++++++++----
>   1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index fed85447701a..c7d8b7c821d8 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2379,7 +2379,7 @@ static void tun_put_page(struct tun_page *tpage)
>   }
>   
>   static int tun_xdp_one(struct tun_struct *tun,
> -		       struct tun_file *tfile,
> +		       struct tun_file *tfile, int *queued,
>   		       struct xdp_buff *xdp, int *flush,
>   		       struct tun_page *tpage)
>   {
> @@ -2388,6 +2388,7 @@ static int tun_xdp_one(struct tun_struct *tun,
>   	struct virtio_net_hdr *gso = &hdr->gso;
>   	struct bpf_prog *xdp_prog;
>   	struct sk_buff *skb = NULL;
> +	struct sk_buff_head *queue;
>   	u32 rxhash = 0, act;
>   	int buflen = hdr->buflen;
>   	int err = 0;
> @@ -2464,7 +2465,15 @@ static int tun_xdp_one(struct tun_struct *tun,
>   	    !tfile->detached)
>   		rxhash = __skb_get_hash_symmetric(skb);
>   
> -	netif_receive_skb(skb);
> +	if (tfile->napi_enabled) {
> +		queue = &tfile->sk.sk_write_queue;
> +		spin_lock(&queue->lock);
> +		__skb_queue_tail(queue, skb);
> +		spin_unlock(&queue->lock);
> +		(*queued)++;
> +	} else {
> +		netif_receive_skb(skb);
> +	}
>   
>   	/* No need to disable preemption here since this function is
>   	 * always called with bh disabled
> @@ -2492,7 +2501,7 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
>   	if (ctl && (ctl->type == TUN_MSG_PTR)) {
>   		struct tun_page tpage;
>   		int n = ctl->num;
> -		int flush = 0;
> +		int flush = 0, queued = 0;
>   
>   		memset(&tpage, 0, sizeof(tpage));
>   
> @@ -2501,12 +2510,15 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
>   
>   		for (i = 0; i < n; i++) {
>   			xdp = &((struct xdp_buff *)ctl->ptr)[i];
> -			tun_xdp_one(tun, tfile, xdp, &flush, &tpage);
> +			tun_xdp_one(tun, tfile, &queued, xdp, &flush, &tpage);


How big n can be ?

BTW I could not find where m->msg_controllen was checked in tun_sendmsg().

struct tun_msg_ctl *ctl = m->msg_control;

if (ctl && (ctl->type == TUN_MSG_PTR)) {

     int n = ctl->num;  // can be set to values in [0..65535]

     for (i = 0; i < n; i++) {

         xdp = &((struct xdp_buff *)ctl->ptr)[i];


I really do not understand how we prevent malicious user space from 
crashing the kernel.



>   		}
>   
>   		if (flush)
>   			xdp_do_flush();
>   
> +		if (tfile->napi_enabled && queued > 0)
> +			napi_schedule(&tfile->napi);
> +
>   		rcu_read_unlock();
>   		local_bh_enable();
>   

Re: [PATCH net-next v2] tun: support NAPI for packets received from batched XDP buffs

[Jason Wang]

On Mon, Feb 28, 2022 at 12:06 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>
> On 2/25/22 01:02, Harold Huang wrote:
> > In tun, NAPI is supported and we can also use NAPI in the path of
> > batched XDP buffs to accelerate packet processing. What is more, after
> > we use NAPI, GRO is also supported. The iperf shows that the throughput of
> > single stream could be improved from 4.5Gbps to 9.2Gbps. Additionally, 9.2
> > Gbps nearly reachs the line speed of the phy nic and there is still about
> > 15% idle cpu core remaining on the vhost thread.
> >
> > Test topology:
> >
> > [iperf server]<--->tap<--->dpdk testpmd<--->phy nic<--->[iperf client]
> >
> > Iperf stream:
> >
> > Before:
> > ...
> > [  5]   5.00-6.00   sec   558 MBytes  4.68 Gbits/sec    0   1.50 MBytes
> > [  5]   6.00-7.00   sec   556 MBytes  4.67 Gbits/sec    1   1.35 MBytes
> > [  5]   7.00-8.00   sec   556 MBytes  4.67 Gbits/sec    2   1.18 MBytes
> > [  5]   8.00-9.00   sec   559 MBytes  4.69 Gbits/sec    0   1.48 MBytes
> > [  5]   9.00-10.00  sec   556 MBytes  4.67 Gbits/sec    1   1.33 MBytes
> > - - - - - - - - - - - - - - - - - - - - - - - - -
> > [ ID] Interval           Transfer     Bitrate         Retr
> > [  5]   0.00-10.00  sec  5.39 GBytes  4.63 Gbits/sec   72          sender
> > [  5]   0.00-10.04  sec  5.39 GBytes  4.61 Gbits/sec               receiver
> >
> > After:
> > ...
> > [  5]   5.00-6.00   sec  1.07 GBytes  9.19 Gbits/sec    0   1.55 MBytes
> > [  5]   6.00-7.00   sec  1.08 GBytes  9.30 Gbits/sec    0   1.63 MBytes
> > [  5]   7.00-8.00   sec  1.08 GBytes  9.25 Gbits/sec    0   1.72 MBytes
> > [  5]   8.00-9.00   sec  1.08 GBytes  9.25 Gbits/sec   77   1.31 MBytes
> > [  5]   9.00-10.00  sec  1.08 GBytes  9.24 Gbits/sec    0   1.48 MBytes
> > - - - - - - - - - - - - - - - - - - - - - - - - -
> > [ ID] Interval           Transfer     Bitrate         Retr
> > [  5]   0.00-10.00  sec  10.8 GBytes  9.28 Gbits/sec  166          sender
> > [  5]   0.00-10.04  sec  10.8 GBytes  9.24 Gbits/sec               receiver
> > ....
> >
> > Reported-at: https://lore.kernel.org/all/CACGkMEvTLG0Ayg+TtbN4q4pPW-ycgCCs3sC3-TF8cuRTf7Pp1A@mail.gmail.com
> > Signed-off-by: Harold Huang <baymaxhuang@gmail.com>
> > ---
> > v1 -> v2
> >   - fix commit messages
> >   - add queued flag to avoid void unnecessary napi suggested by Jason
> >
> >   drivers/net/tun.c | 20 ++++++++++++++++----
> >   1 file changed, 16 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > index fed85447701a..c7d8b7c821d8 100644
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -2379,7 +2379,7 @@ static void tun_put_page(struct tun_page *tpage)
> >   }
> >
> >   static int tun_xdp_one(struct tun_struct *tun,
> > -                    struct tun_file *tfile,
> > +                    struct tun_file *tfile, int *queued,
> >                      struct xdp_buff *xdp, int *flush,
> >                      struct tun_page *tpage)
> >   {
> > @@ -2388,6 +2388,7 @@ static int tun_xdp_one(struct tun_struct *tun,
> >       struct virtio_net_hdr *gso = &hdr->gso;
> >       struct bpf_prog *xdp_prog;
> >       struct sk_buff *skb = NULL;
> > +     struct sk_buff_head *queue;
> >       u32 rxhash = 0, act;
> >       int buflen = hdr->buflen;
> >       int err = 0;
> > @@ -2464,7 +2465,15 @@ static int tun_xdp_one(struct tun_struct *tun,
> >           !tfile->detached)
> >               rxhash = __skb_get_hash_symmetric(skb);
> >
> > -     netif_receive_skb(skb);
> > +     if (tfile->napi_enabled) {
> > +             queue = &tfile->sk.sk_write_queue;
> > +             spin_lock(&queue->lock);
> > +             __skb_queue_tail(queue, skb);
> > +             spin_unlock(&queue->lock);
> > +             (*queued)++;
> > +     } else {
> > +             netif_receive_skb(skb);
> > +     }
> >
> >       /* No need to disable preemption here since this function is
> >        * always called with bh disabled
> > @@ -2492,7 +2501,7 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
> >       if (ctl && (ctl->type == TUN_MSG_PTR)) {
> >               struct tun_page tpage;
> >               int n = ctl->num;
> > -             int flush = 0;
> > +             int flush = 0, queued = 0;
> >
> >               memset(&tpage, 0, sizeof(tpage));
> >
> > @@ -2501,12 +2510,15 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
> >
> >               for (i = 0; i < n; i++) {
> >                       xdp = &((struct xdp_buff *)ctl->ptr)[i];
> > -                     tun_xdp_one(tun, tfile, xdp, &flush, &tpage);
> > +                     tun_xdp_one(tun, tfile, &queued, xdp, &flush, &tpage);
>
>
> How big n can be ?
>
> BTW I could not find where m->msg_controllen was checked in tun_sendmsg().
>
> struct tun_msg_ctl *ctl = m->msg_control;
>
> if (ctl && (ctl->type == TUN_MSG_PTR)) {
>
>      int n = ctl->num;  // can be set to values in [0..65535]
>
>      for (i = 0; i < n; i++) {
>
>          xdp = &((struct xdp_buff *)ctl->ptr)[i];
>
>
> I really do not understand how we prevent malicious user space from
> crashing the kernel.

It looks to me the only user for this is vhost-net which limits it to
64, userspace can't use sendmsg() directly on tap.

Thanks

>
>
>
> >               }
> >
> >               if (flush)
> >                       xdp_do_flush();
> >
> > +             if (tfile->napi_enabled && queued > 0)
> > +                     napi_schedule(&tfile->napi);
> > +
> >               rcu_read_unlock();
> >               local_bh_enable();
> >
>

Re: [PATCH net-next v2] tun: support NAPI for packets received from batched XDP buffs

[Jason Wang]

On Mon, Feb 28, 2022 at 12:59 PM Eric Dumazet <edumazet@google.com> wrote:
>
>
>
> On Sun, Feb 27, 2022 at 8:20 PM Jason Wang <jasowang@redhat.com> wrote:
>>
>> On Mon, Feb 28, 2022 at 12:06 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>>
>> > How big n can be ?
>> >
>> > BTW I could not find where m->msg_controllen was checked in tun_sendmsg().
>> >
>> > struct tun_msg_ctl *ctl = m->msg_control;
>> >
>> > if (ctl && (ctl->type == TUN_MSG_PTR)) {
>> >
>> >      int n = ctl->num;  // can be set to values in [0..65535]
>> >
>> >      for (i = 0; i < n; i++) {
>> >
>> >          xdp = &((struct xdp_buff *)ctl->ptr)[i];
>> >
>> >
>> > I really do not understand how we prevent malicious user space from
>> > crashing the kernel.
>>
>> It looks to me the only user for this is vhost-net which limits it to
>> 64, userspace can't use sendmsg() directly on tap.
>>
>
> Ah right, thanks for the clarification.
>
> (IMO, either remove the "msg.msg_controllen = sizeof(ctl);" from handle_tx_zerocopy(), or add sanity checks in tun_sendmsg())
>
>

Right, Harold, want to do that?

Thanks

Re: [PATCH net-next v2] tun: support NAPI for packets received from batched XDP buffs

[Harold Huang]

Thanks for the suggestions.

On Mon, Feb 28, 2022 at 1:17 PM Jason Wang <jasowang@redhat.com> wrote:
>
> On Mon, Feb 28, 2022 at 12:59 PM Eric Dumazet <edumazet@google.com> wrote:
> >
> >
> >
> > On Sun, Feb 27, 2022 at 8:20 PM Jason Wang <jasowang@redhat.com> wrote:
> >>
> >> On Mon, Feb 28, 2022 at 12:06 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
> >>
> >> > How big n can be ?
> >> >
> >> > BTW I could not find where m->msg_controllen was checked in tun_sendmsg().
> >> >
> >> > struct tun_msg_ctl *ctl = m->msg_control;
> >> >
> >> > if (ctl && (ctl->type == TUN_MSG_PTR)) {
> >> >
> >> >      int n = ctl->num;  // can be set to values in [0..65535]
> >> >
> >> >      for (i = 0; i < n; i++) {
> >> >
> >> >          xdp = &((struct xdp_buff *)ctl->ptr)[i];
> >> >
> >> >
> >> > I really do not understand how we prevent malicious user space from
> >> > crashing the kernel.
> >>
> >> It looks to me the only user for this is vhost-net which limits it to
> >> 64, userspace can't use sendmsg() directly on tap.
> >>
> >
> > Ah right, thanks for the clarification.
> >
> > (IMO, either remove the "msg.msg_controllen = sizeof(ctl);" from handle_tx_zerocopy(), or add sanity checks in tun_sendmsg())
> >
> >
>
> Right, Harold, want to do that?

I am greatly willing to do that. But  I am not quite sure about this.

If we remove the "msg.msg_controllen = sizeof(ctl);" from
handle_tx_zerocopy(), it seems msg.msg_controllen is always 0. What
does it stands for?

I see tap_sendmsg in drivers/net/tap.c also uses msg_controller to
send batched xdp buffers. Do we need to add similar sanity checks to
tap_sendmsg  as tun_sendmsg?

Re: [PATCH net-next v2] tun: support NAPI for packets received from batched XDP buffs

[Jason Wang]

On Mon, Feb 28, 2022 at 3:27 PM Harold Huang <baymaxhuang@gmail.com> wrote:
>
> Thanks for the suggestions.
>
> On Mon, Feb 28, 2022 at 1:17 PM Jason Wang <jasowang@redhat.com> wrote:
> >
> > On Mon, Feb 28, 2022 at 12:59 PM Eric Dumazet <edumazet@google.com> wrote:
> > >
> > >
> > >
> > > On Sun, Feb 27, 2022 at 8:20 PM Jason Wang <jasowang@redhat.com> wrote:
> > >>
> > >> On Mon, Feb 28, 2022 at 12:06 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > >>
> > >> > How big n can be ?
> > >> >
> > >> > BTW I could not find where m->msg_controllen was checked in tun_sendmsg().
> > >> >
> > >> > struct tun_msg_ctl *ctl = m->msg_control;
> > >> >
> > >> > if (ctl && (ctl->type == TUN_MSG_PTR)) {
> > >> >
> > >> >      int n = ctl->num;  // can be set to values in [0..65535]
> > >> >
> > >> >      for (i = 0; i < n; i++) {
> > >> >
> > >> >          xdp = &((struct xdp_buff *)ctl->ptr)[i];
> > >> >
> > >> >
> > >> > I really do not understand how we prevent malicious user space from
> > >> > crashing the kernel.
> > >>
> > >> It looks to me the only user for this is vhost-net which limits it to
> > >> 64, userspace can't use sendmsg() directly on tap.
> > >>
> > >
> > > Ah right, thanks for the clarification.
> > >
> > > (IMO, either remove the "msg.msg_controllen = sizeof(ctl);" from handle_tx_zerocopy(), or add sanity checks in tun_sendmsg())
> > >
> > >
> >
> > Right, Harold, want to do that?
>
> I am greatly willing to do that. But  I am not quite sure about this.
>
> If we remove the "msg.msg_controllen = sizeof(ctl);" from
> handle_tx_zerocopy(), it seems msg.msg_controllen is always 0. What
> does it stands for?

It means msg_controllen is not used. But see below (adding sanity
check seems to be better).

>
> I see tap_sendmsg in drivers/net/tap.c also uses msg_controller to
> send batched xdp buffers. Do we need to add similar sanity checks to
> tap_sendmsg  as tun_sendmsg?
>

I think the point is to make sure the caller doesn't send us too short
msg_control. E.g the msg_controllen should be sizeof(tun_msg_ctl).

So we probably need to check in both places. (And initialize
msg_controllen is vhost_tx_batch())

Thanks

[PATCH net-next v3] tun: support NAPI for packets received from batched XDP buffs

[Harold Huang]

In tun, NAPI is supported and we can also use NAPI in the path of
batched XDP buffs to accelerate packet processing. What is more, after
we use NAPI, GRO is also supported. The iperf shows that the throughput of
single stream could be improved from 4.5Gbps to 9.2Gbps. Additionally, 9.2
Gbps nearly reachs the line speed of the phy nic and there is still about
15% idle cpu core remaining on the vhost thread.

Test topology:
[iperf server]<--->tap<--->dpdk testpmd<--->phy nic<--->[iperf client]

Iperf stream:
iperf3 -c 10.0.0.2  -i 1 -t 10

Before:
...
[  5]   5.00-6.00   sec   558 MBytes  4.68 Gbits/sec    0   1.50 MBytes
[  5]   6.00-7.00   sec   556 MBytes  4.67 Gbits/sec    1   1.35 MBytes
[  5]   7.00-8.00   sec   556 MBytes  4.67 Gbits/sec    2   1.18 MBytes
[  5]   8.00-9.00   sec   559 MBytes  4.69 Gbits/sec    0   1.48 MBytes
[  5]   9.00-10.00  sec   556 MBytes  4.67 Gbits/sec    1   1.33 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  5.39 GBytes  4.63 Gbits/sec   72          sender
[  5]   0.00-10.04  sec  5.39 GBytes  4.61 Gbits/sec               receiver

After:
...
[  5]   5.00-6.00   sec  1.07 GBytes  9.19 Gbits/sec    0   1.55 MBytes
[  5]   6.00-7.00   sec  1.08 GBytes  9.30 Gbits/sec    0   1.63 MBytes
[  5]   7.00-8.00   sec  1.08 GBytes  9.25 Gbits/sec    0   1.72 MBytes
[  5]   8.00-9.00   sec  1.08 GBytes  9.25 Gbits/sec   77   1.31 MBytes
[  5]   9.00-10.00  sec  1.08 GBytes  9.24 Gbits/sec    0   1.48 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  10.8 GBytes  9.28 Gbits/sec  166          sender
[  5]   0.00-10.04  sec  10.8 GBytes  9.24 Gbits/sec               receiver

Reported-at: https://lore.kernel.org/all/CACGkMEvTLG0Ayg+TtbN4q4pPW-ycgCCs3sC3-TF8cuRTf7Pp1A@mail.gmail.com
Signed-off-by: Harold Huang <baymaxhuang@gmail.com>
---
v2 -> v3
 - return the queued NAPI packet from tun_xdp_one

 drivers/net/tun.c | 43 ++++++++++++++++++++++++++++++-------------
 1 file changed, 30 insertions(+), 13 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index fed85447701a..969ea69fd29d 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2388,9 +2388,10 @@ static int tun_xdp_one(struct tun_struct *tun,
 	struct virtio_net_hdr *gso = &hdr->gso;
 	struct bpf_prog *xdp_prog;
 	struct sk_buff *skb = NULL;
+	struct sk_buff_head *queue;
 	u32 rxhash = 0, act;
 	int buflen = hdr->buflen;
-	int err = 0;
+	int ret = 0;
 	bool skb_xdp = false;
 	struct page *page;
 
@@ -2405,13 +2406,13 @@ static int tun_xdp_one(struct tun_struct *tun,
 		xdp_set_data_meta_invalid(xdp);
 
 		act = bpf_prog_run_xdp(xdp_prog, xdp);
-		err = tun_xdp_act(tun, xdp_prog, xdp, act);
-		if (err < 0) {
+		ret = tun_xdp_act(tun, xdp_prog, xdp, act);
+		if (ret < 0) {
 			put_page(virt_to_head_page(xdp->data));
-			return err;
+			return ret;
 		}
 
-		switch (err) {
+		switch (ret) {
 		case XDP_REDIRECT:
 			*flush = true;
 			fallthrough;
@@ -2435,7 +2436,7 @@ static int tun_xdp_one(struct tun_struct *tun,
 build:
 	skb = build_skb(xdp->data_hard_start, buflen);
 	if (!skb) {
-		err = -ENOMEM;
+		ret = -ENOMEM;
 		goto out;
 	}
 
@@ -2445,7 +2446,7 @@ static int tun_xdp_one(struct tun_struct *tun,
 	if (virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
 		atomic_long_inc(&tun->rx_frame_errors);
 		kfree_skb(skb);
-		err = -EINVAL;
+		ret = -EINVAL;
 		goto out;
 	}
 
@@ -2455,16 +2456,27 @@ static int tun_xdp_one(struct tun_struct *tun,
 	skb_record_rx_queue(skb, tfile->queue_index);
 
 	if (skb_xdp) {
-		err = do_xdp_generic(xdp_prog, skb);
-		if (err != XDP_PASS)
+		ret = do_xdp_generic(xdp_prog, skb);
+		if (ret != XDP_PASS) {
+			ret = 0;
 			goto out;
+		}
 	}
 
 	if (!rcu_dereference(tun->steering_prog) && tun->numqueues > 1 &&
 	    !tfile->detached)
 		rxhash = __skb_get_hash_symmetric(skb);
 
-	netif_receive_skb(skb);
+	if (tfile->napi_enabled) {
+		queue = &tfile->sk.sk_write_queue;
+		spin_lock(&queue->lock);
+		__skb_queue_tail(queue, skb);
+		spin_unlock(&queue->lock);
+		ret = 1;
+	} else {
+		netif_receive_skb(skb);
+		ret = 0;
+	}
 
 	/* No need to disable preemption here since this function is
 	 * always called with bh disabled
@@ -2475,7 +2487,7 @@ static int tun_xdp_one(struct tun_struct *tun,
 		tun_flow_update(tun, rxhash, tfile);
 
 out:
-	return err;
+	return ret;
 }
 
 static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
@@ -2492,7 +2504,7 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 	if (ctl && (ctl->type == TUN_MSG_PTR)) {
 		struct tun_page tpage;
 		int n = ctl->num;
-		int flush = 0;
+		int flush = 0, queued = 0;
 
 		memset(&tpage, 0, sizeof(tpage));
 
@@ -2501,12 +2513,17 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 
 		for (i = 0; i < n; i++) {
 			xdp = &((struct xdp_buff *)ctl->ptr)[i];
-			tun_xdp_one(tun, tfile, xdp, &flush, &tpage);
+			ret = tun_xdp_one(tun, tfile, xdp, &flush, &tpage);
+			if (ret > 0)
+				queued += ret;
 		}
 
 		if (flush)
 			xdp_do_flush();
 
+		if (tfile->napi_enabled && queued > 0)
+			napi_schedule(&tfile->napi);
+
 		rcu_read_unlock();
 		local_bh_enable();
 
-- 
2.27.0

Re: [PATCH net-next v3] tun: support NAPI for packets received from batched XDP buffs

[Jason Wang]

On Mon, Feb 28, 2022 at 11:38 AM Harold Huang <baymaxhuang@gmail.com> wrote:
>
> In tun, NAPI is supported and we can also use NAPI in the path of
> batched XDP buffs to accelerate packet processing. What is more, after
> we use NAPI, GRO is also supported. The iperf shows that the throughput of
> single stream could be improved from 4.5Gbps to 9.2Gbps. Additionally, 9.2
> Gbps nearly reachs the line speed of the phy nic and there is still about
> 15% idle cpu core remaining on the vhost thread.
>
> Test topology:
> [iperf server]<--->tap<--->dpdk testpmd<--->phy nic<--->[iperf client]
>
> Iperf stream:
> iperf3 -c 10.0.0.2  -i 1 -t 10
>
> Before:
> ...
> [  5]   5.00-6.00   sec   558 MBytes  4.68 Gbits/sec    0   1.50 MBytes
> [  5]   6.00-7.00   sec   556 MBytes  4.67 Gbits/sec    1   1.35 MBytes
> [  5]   7.00-8.00   sec   556 MBytes  4.67 Gbits/sec    2   1.18 MBytes
> [  5]   8.00-9.00   sec   559 MBytes  4.69 Gbits/sec    0   1.48 MBytes
> [  5]   9.00-10.00  sec   556 MBytes  4.67 Gbits/sec    1   1.33 MBytes
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-10.00  sec  5.39 GBytes  4.63 Gbits/sec   72          sender
> [  5]   0.00-10.04  sec  5.39 GBytes  4.61 Gbits/sec               receiver
>
> After:
> ...
> [  5]   5.00-6.00   sec  1.07 GBytes  9.19 Gbits/sec    0   1.55 MBytes
> [  5]   6.00-7.00   sec  1.08 GBytes  9.30 Gbits/sec    0   1.63 MBytes
> [  5]   7.00-8.00   sec  1.08 GBytes  9.25 Gbits/sec    0   1.72 MBytes
> [  5]   8.00-9.00   sec  1.08 GBytes  9.25 Gbits/sec   77   1.31 MBytes
> [  5]   9.00-10.00  sec  1.08 GBytes  9.24 Gbits/sec    0   1.48 MBytes
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-10.00  sec  10.8 GBytes  9.28 Gbits/sec  166          sender
> [  5]   0.00-10.04  sec  10.8 GBytes  9.24 Gbits/sec               receiver
>
> Reported-at: https://lore.kernel.org/all/CACGkMEvTLG0Ayg+TtbN4q4pPW-ycgCCs3sC3-TF8cuRTf7Pp1A@mail.gmail.com
> Signed-off-by: Harold Huang <baymaxhuang@gmail.com>

Acked-by: Jason Wang <jasowang@redhat.com>

> ---
> v2 -> v3
>  - return the queued NAPI packet from tun_xdp_one
>
>  drivers/net/tun.c | 43 ++++++++++++++++++++++++++++++-------------
>  1 file changed, 30 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index fed85447701a..969ea69fd29d 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2388,9 +2388,10 @@ static int tun_xdp_one(struct tun_struct *tun,
>         struct virtio_net_hdr *gso = &hdr->gso;
>         struct bpf_prog *xdp_prog;
>         struct sk_buff *skb = NULL;
> +       struct sk_buff_head *queue;
>         u32 rxhash = 0, act;
>         int buflen = hdr->buflen;
> -       int err = 0;
> +       int ret = 0;
>         bool skb_xdp = false;
>         struct page *page;
>
> @@ -2405,13 +2406,13 @@ static int tun_xdp_one(struct tun_struct *tun,
>                 xdp_set_data_meta_invalid(xdp);
>
>                 act = bpf_prog_run_xdp(xdp_prog, xdp);
> -               err = tun_xdp_act(tun, xdp_prog, xdp, act);
> -               if (err < 0) {
> +               ret = tun_xdp_act(tun, xdp_prog, xdp, act);
> +               if (ret < 0) {
>                         put_page(virt_to_head_page(xdp->data));
> -                       return err;
> +                       return ret;
>                 }
>
> -               switch (err) {
> +               switch (ret) {
>                 case XDP_REDIRECT:
>                         *flush = true;
>                         fallthrough;
> @@ -2435,7 +2436,7 @@ static int tun_xdp_one(struct tun_struct *tun,
>  build:
>         skb = build_skb(xdp->data_hard_start, buflen);
>         if (!skb) {
> -               err = -ENOMEM;
> +               ret = -ENOMEM;
>                 goto out;
>         }
>
> @@ -2445,7 +2446,7 @@ static int tun_xdp_one(struct tun_struct *tun,
>         if (virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
>                 atomic_long_inc(&tun->rx_frame_errors);
>                 kfree_skb(skb);
> -               err = -EINVAL;
> +               ret = -EINVAL;
>                 goto out;
>         }
>
> @@ -2455,16 +2456,27 @@ static int tun_xdp_one(struct tun_struct *tun,
>         skb_record_rx_queue(skb, tfile->queue_index);
>
>         if (skb_xdp) {
> -               err = do_xdp_generic(xdp_prog, skb);
> -               if (err != XDP_PASS)
> +               ret = do_xdp_generic(xdp_prog, skb);
> +               if (ret != XDP_PASS) {
> +                       ret = 0;
>                         goto out;
> +               }
>         }
>
>         if (!rcu_dereference(tun->steering_prog) && tun->numqueues > 1 &&
>             !tfile->detached)
>                 rxhash = __skb_get_hash_symmetric(skb);
>
> -       netif_receive_skb(skb);
> +       if (tfile->napi_enabled) {
> +               queue = &tfile->sk.sk_write_queue;
> +               spin_lock(&queue->lock);
> +               __skb_queue_tail(queue, skb);
> +               spin_unlock(&queue->lock);
> +               ret = 1;
> +       } else {
> +               netif_receive_skb(skb);
> +               ret = 0;
> +       }
>
>         /* No need to disable preemption here since this function is
>          * always called with bh disabled
> @@ -2475,7 +2487,7 @@ static int tun_xdp_one(struct tun_struct *tun,
>                 tun_flow_update(tun, rxhash, tfile);
>
>  out:
> -       return err;
> +       return ret;
>  }
>
>  static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
> @@ -2492,7 +2504,7 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
>         if (ctl && (ctl->type == TUN_MSG_PTR)) {
>                 struct tun_page tpage;
>                 int n = ctl->num;
> -               int flush = 0;
> +               int flush = 0, queued = 0;
>
>                 memset(&tpage, 0, sizeof(tpage));
>
> @@ -2501,12 +2513,17 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
>
>                 for (i = 0; i < n; i++) {
>                         xdp = &((struct xdp_buff *)ctl->ptr)[i];
> -                       tun_xdp_one(tun, tfile, xdp, &flush, &tpage);
> +                       ret = tun_xdp_one(tun, tfile, xdp, &flush, &tpage);
> +                       if (ret > 0)
> +                               queued += ret;
>                 }
>
>                 if (flush)
>                         xdp_do_flush();
>
> +               if (tfile->napi_enabled && queued > 0)
> +                       napi_schedule(&tfile->napi);
> +
>                 rcu_read_unlock();
>                 local_bh_enable();
>
> --
> 2.27.0
>

Re: [PATCH net-next v3] tun: support NAPI for packets received from batched XDP buffs

[Stephen Hemminger]

On Mon, 28 Feb 2022 15:46:56 +0800
Jason Wang <jasowang@redhat.com> wrote:

> On Mon, Feb 28, 2022 at 11:38 AM Harold Huang <baymaxhuang@gmail.com> wrote:
> >
> > In tun, NAPI is supported and we can also use NAPI in the path of
> > batched XDP buffs to accelerate packet processing. What is more, after
> > we use NAPI, GRO is also supported. The iperf shows that the throughput of
> > single stream could be improved from 4.5Gbps to 9.2Gbps. Additionally, 9.2
> > Gbps nearly reachs the line speed of the phy nic and there is still about
> > 15% idle cpu core remaining on the vhost thread.
> >
> > Test topology:
> > [iperf server]<--->tap<--->dpdk testpmd<--->phy nic<--->[iperf client]
> >
> > Iperf stream:
> > iperf3 -c 10.0.0.2  -i 1 -t 10
> >
> > Before:
> > ...
> > [  5]   5.00-6.00   sec   558 MBytes  4.68 Gbits/sec    0   1.50 MBytes
> > [  5]   6.00-7.00   sec   556 MBytes  4.67 Gbits/sec    1   1.35 MBytes
> > [  5]   7.00-8.00   sec   556 MBytes  4.67 Gbits/sec    2   1.18 MBytes
> > [  5]   8.00-9.00   sec   559 MBytes  4.69 Gbits/sec    0   1.48 MBytes
> > [  5]   9.00-10.00  sec   556 MBytes  4.67 Gbits/sec    1   1.33 MBytes
> > - - - - - - - - - - - - - - - - - - - - - - - - -
> > [ ID] Interval           Transfer     Bitrate         Retr
> > [  5]   0.00-10.00  sec  5.39 GBytes  4.63 Gbits/sec   72          sender
> > [  5]   0.00-10.04  sec  5.39 GBytes  4.61 Gbits/sec               receiver
> >
> > After:
> > ...
> > [  5]   5.00-6.00   sec  1.07 GBytes  9.19 Gbits/sec    0   1.55 MBytes
> > [  5]   6.00-7.00   sec  1.08 GBytes  9.30 Gbits/sec    0   1.63 MBytes
> > [  5]   7.00-8.00   sec  1.08 GBytes  9.25 Gbits/sec    0   1.72 MBytes
> > [  5]   8.00-9.00   sec  1.08 GBytes  9.25 Gbits/sec   77   1.31 MBytes
> > [  5]   9.00-10.00  sec  1.08 GBytes  9.24 Gbits/sec    0   1.48 MBytes
> > - - - - - - - - - - - - - - - - - - - - - - - - -
> > [ ID] Interval           Transfer     Bitrate         Retr
> > [  5]   0.00-10.00  sec  10.8 GBytes  9.28 Gbits/sec  166          sender
> > [  5]   0.00-10.04  sec  10.8 GBytes  9.24 Gbits/sec               receiver
> >
> > Reported-at: https://lore.kernel.org/all/CACGkMEvTLG0Ayg+TtbN4q4pPW-ycgCCs3sC3-TF8cuRTf7Pp1A@mail.gmail.com
> > Signed-off-by: Harold Huang <baymaxhuang@gmail.com>  
> 
> Acked-by: Jason Wang <jasowang@redhat.com>

Would this help when using sendmmsg and recvmmsg on the TAP device?
Asking because interested in speeding up another use of TAP device, and wondering
if this would help.

Re: [PATCH net-next v3] tun: support NAPI for packets received from batched XDP buffs

[Jason Wang]

On Tue, Mar 1, 2022 at 1:15 AM Stephen Hemminger
<stephen@networkplumber.org> wrote:
>
> On Mon, 28 Feb 2022 15:46:56 +0800
> Jason Wang <jasowang@redhat.com> wrote:
>
> > On Mon, Feb 28, 2022 at 11:38 AM Harold Huang <baymaxhuang@gmail.com> wrote:
> > >
> > > In tun, NAPI is supported and we can also use NAPI in the path of
> > > batched XDP buffs to accelerate packet processing. What is more, after
> > > we use NAPI, GRO is also supported. The iperf shows that the throughput of
> > > single stream could be improved from 4.5Gbps to 9.2Gbps. Additionally, 9.2
> > > Gbps nearly reachs the line speed of the phy nic and there is still about
> > > 15% idle cpu core remaining on the vhost thread.
> > >
> > > Test topology:
> > > [iperf server]<--->tap<--->dpdk testpmd<--->phy nic<--->[iperf client]
> > >
> > > Iperf stream:
> > > iperf3 -c 10.0.0.2  -i 1 -t 10
> > >
> > > Before:
> > > ...
> > > [  5]   5.00-6.00   sec   558 MBytes  4.68 Gbits/sec    0   1.50 MBytes
> > > [  5]   6.00-7.00   sec   556 MBytes  4.67 Gbits/sec    1   1.35 MBytes
> > > [  5]   7.00-8.00   sec   556 MBytes  4.67 Gbits/sec    2   1.18 MBytes
> > > [  5]   8.00-9.00   sec   559 MBytes  4.69 Gbits/sec    0   1.48 MBytes
> > > [  5]   9.00-10.00  sec   556 MBytes  4.67 Gbits/sec    1   1.33 MBytes
> > > - - - - - - - - - - - - - - - - - - - - - - - - -
> > > [ ID] Interval           Transfer     Bitrate         Retr
> > > [  5]   0.00-10.00  sec  5.39 GBytes  4.63 Gbits/sec   72          sender
> > > [  5]   0.00-10.04  sec  5.39 GBytes  4.61 Gbits/sec               receiver
> > >
> > > After:
> > > ...
> > > [  5]   5.00-6.00   sec  1.07 GBytes  9.19 Gbits/sec    0   1.55 MBytes
> > > [  5]   6.00-7.00   sec  1.08 GBytes  9.30 Gbits/sec    0   1.63 MBytes
> > > [  5]   7.00-8.00   sec  1.08 GBytes  9.25 Gbits/sec    0   1.72 MBytes
> > > [  5]   8.00-9.00   sec  1.08 GBytes  9.25 Gbits/sec   77   1.31 MBytes
> > > [  5]   9.00-10.00  sec  1.08 GBytes  9.24 Gbits/sec    0   1.48 MBytes
> > > - - - - - - - - - - - - - - - - - - - - - - - - -
> > > [ ID] Interval           Transfer     Bitrate         Retr
> > > [  5]   0.00-10.00  sec  10.8 GBytes  9.28 Gbits/sec  166          sender
> > > [  5]   0.00-10.04  sec  10.8 GBytes  9.24 Gbits/sec               receiver
> > >
> > > Reported-at: https://lore.kernel.org/all/CACGkMEvTLG0Ayg+TtbN4q4pPW-ycgCCs3sC3-TF8cuRTf7Pp1A@mail.gmail.com
> > > Signed-off-by: Harold Huang <baymaxhuang@gmail.com>
> >
> > Acked-by: Jason Wang <jasowang@redhat.com>
>
> Would this help when using sendmmsg and recvmmsg on the TAP device?

We haven't exported the socket object of tuntap to userspace. So we
can't use sendmmsg()/recvmsg() now.

> Asking because interested in speeding up another use of TAP device, and wondering
> if this would help.
>

Yes, it would be interesting. We need someone to work on that.

Thanks

Re: [PATCH net-next v3] tun: support NAPI for packets received from batched XDP buffs

[Harold Huang]

On Tue, Mar 1, 2022 at 1:15 AM Stephen Hemminger
<stephen@networkplumber.org> wrote:
>
> On Mon, 28 Feb 2022 15:46:56 +0800
> Jason Wang <jasowang@redhat.com> wrote:
>
> > On Mon, Feb 28, 2022 at 11:38 AM Harold Huang <baymaxhuang@gmail.com> wrote:
> > >
> > > In tun, NAPI is supported and we can also use NAPI in the path of
> > > batched XDP buffs to accelerate packet processing. What is more, after
> > > we use NAPI, GRO is also supported. The iperf shows that the throughput of
> > > single stream could be improved from 4.5Gbps to 9.2Gbps. Additionally, 9.2
> > > Gbps nearly reachs the line speed of the phy nic and there is still about
> > > 15% idle cpu core remaining on the vhost thread.
> > >
> > > Test topology:
> > > [iperf server]<--->tap<--->dpdk testpmd<--->phy nic<--->[iperf client]
> > >
> > > Iperf stream:
> > > iperf3 -c 10.0.0.2  -i 1 -t 10
> > >
> > > Before:
> > > ...
> > > [  5]   5.00-6.00   sec   558 MBytes  4.68 Gbits/sec    0   1.50 MBytes
> > > [  5]   6.00-7.00   sec   556 MBytes  4.67 Gbits/sec    1   1.35 MBytes
> > > [  5]   7.00-8.00   sec   556 MBytes  4.67 Gbits/sec    2   1.18 MBytes
> > > [  5]   8.00-9.00   sec   559 MBytes  4.69 Gbits/sec    0   1.48 MBytes
> > > [  5]   9.00-10.00  sec   556 MBytes  4.67 Gbits/sec    1   1.33 MBytes
> > > - - - - - - - - - - - - - - - - - - - - - - - - -
> > > [ ID] Interval           Transfer     Bitrate         Retr
> > > [  5]   0.00-10.00  sec  5.39 GBytes  4.63 Gbits/sec   72          sender
> > > [  5]   0.00-10.04  sec  5.39 GBytes  4.61 Gbits/sec               receiver
> > >
> > > After:
> > > ...
> > > [  5]   5.00-6.00   sec  1.07 GBytes  9.19 Gbits/sec    0   1.55 MBytes
> > > [  5]   6.00-7.00   sec  1.08 GBytes  9.30 Gbits/sec    0   1.63 MBytes
> > > [  5]   7.00-8.00   sec  1.08 GBytes  9.25 Gbits/sec    0   1.72 MBytes
> > > [  5]   8.00-9.00   sec  1.08 GBytes  9.25 Gbits/sec   77   1.31 MBytes
> > > [  5]   9.00-10.00  sec  1.08 GBytes  9.24 Gbits/sec    0   1.48 MBytes
> > > - - - - - - - - - - - - - - - - - - - - - - - - -
> > > [ ID] Interval           Transfer     Bitrate         Retr
> > > [  5]   0.00-10.00  sec  10.8 GBytes  9.28 Gbits/sec  166          sender
> > > [  5]   0.00-10.04  sec  10.8 GBytes  9.24 Gbits/sec               receiver
> > >
> > > Reported-at: https://lore.kernel.org/all/CACGkMEvTLG0Ayg+TtbN4q4pPW-ycgCCs3sC3-TF8cuRTf7Pp1A@mail.gmail.com
> > > Signed-off-by: Harold Huang <baymaxhuang@gmail.com>
> >
> > Acked-by: Jason Wang <jasowang@redhat.com>
>
> Would this help when using sendmmsg and recvmmsg on the TAP device?
> Asking because interested in speeding up another use of TAP device, and wondering
> if this would help.

As Jason said, sendmmsg()/recvmsg() could not be used on tuntap. But I
think another choice is to use writev/readv directly on the ttunap fd,
which will call tun_get_user to send msg and NAPI has also been
supported.

Re: [PATCH net-next v3] tun: support NAPI for packets received from batched XDP buffs

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 28 Feb 2022 11:38:05 +0800 you wrote:
> In tun, NAPI is supported and we can also use NAPI in the path of
> batched XDP buffs to accelerate packet processing. What is more, after
> we use NAPI, GRO is also supported. The iperf shows that the throughput of
> single stream could be improved from 4.5Gbps to 9.2Gbps. Additionally, 9.2
> Gbps nearly reachs the line speed of the phy nic and there is still about
> 15% idle cpu core remaining on the vhost thread.
> 
> [...]

Here is the summary with links:
  - [net-next,v3] tun: support NAPI for packets received from batched XDP buffs
    https://git.kernel.org/netdev/net-next/c/fb3f903769e8

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
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