[PATCH net-next 1/2] net: introduce skb_coalesce_rx_frag()

[PATCH net-next 1/2] net: introduce skb_coalesce_rx_frag()

[Jason Wang]

Sometimes we need to coalesce the rx frags to avoid frag list. One example is
virtio-net driver which tries to use small frags for both MTU sized packet and
GSO packet. So this patch introduce skb_coalesce_rx_frag() to do this.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Michael Dalton <mwdalton@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 include/linux/skbuff.h |  3 +++
 net/core/skbuff.c      | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2c15497..e34652b 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1372,6 +1372,9 @@ static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
 void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
 		     int size, unsigned int truesize);
 
+void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int off, int size,
+			  unsigned int truesize);
+
 #define SKB_PAGE_ASSERT(skb) 	BUG_ON(skb_shinfo(skb)->nr_frags)
 #define SKB_FRAG_ASSERT(skb) 	BUG_ON(skb_has_frag_list(skb))
 #define SKB_LINEAR_ASSERT(skb)  BUG_ON(skb_is_nonlinear(skb))
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 0ab32fa..fdef994 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -476,6 +476,19 @@ void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
 }
 EXPORT_SYMBOL(skb_add_rx_frag);
 
+void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int off, int size,
+			  unsigned int truesize)
+{
+	skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+
+	skb_frag_size_add(frag, size);
+	skb->len += size;
+	skb->data_len += size;
+	skb->truesize += truesize;
+	skb_frag_unref(skb, i);
+}
+EXPORT_SYMBOL(skb_coalesce_rx_frag);
+
 static void skb_drop_list(struct sk_buff **listp)
 {
 	kfree_skb_list(*listp);
-- 
1.8.1.2

[PATCH net-next 2/2] virtio-net: coalesce rx frags when possible during rx

[Jason Wang]

Commit 2613af0ed18a11d5c566a81f9a6510b73180660a (virtio_net: migrate mergeable
rx buffers to page frag allocators) try to increase the payload/truesize for
MTU-sized traffic. But this will introduce the extra overhead for GSO packets
received because of the frag list. This commit tries to reduce this issue by
coalesce the possible rx frags when possible during rx. Test result shows the
about 15% improvement on full size GSO packet receiving (and even better than
commit 2613af0ed18a11d5c566a81f9a6510b73180660a).

Before this commit:
./netperf -H 192.168.100.4
MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.100.4
() port 0 AF_INET : demo
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

 87380  16384  16384    10.00    20303.87

After this commit:
./netperf -H 192.168.100.4
MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.100.4 () port 0 AF_INET : demo
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

 87380  16384  16384    10.00    23841.26

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Michael Dalton <mwdalton@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/virtio_net.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 113ee93..4ff4f78 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -305,7 +305,7 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *head_skb)
 	struct sk_buff *curr_skb = head_skb;
 	char *buf;
 	struct page *page;
-	int num_buf, len;
+	int num_buf, len, offset;
 
 	num_buf = hdr->mhdr.num_buffers;
 	while (--num_buf) {
@@ -342,9 +342,15 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *head_skb)
 			head_skb->truesize += MAX_PACKET_LEN;
 		}
 		page = virt_to_head_page(buf);
-		skb_add_rx_frag(curr_skb, num_skb_frags, page,
-				buf - (char *)page_address(page), len,
-				MAX_PACKET_LEN);
+		offset = buf - (char *)page_address(page);
+		if (skb_can_coalesce(curr_skb, num_skb_frags, page, offset)) {
+			skb_coalesce_rx_frag(curr_skb, num_skb_frags - 1,
+					     offset, len, MAX_PACKET_LEN);
+		} else {
+			skb_add_rx_frag(curr_skb, num_skb_frags, page,
+					offset, len,
+					MAX_PACKET_LEN);
+		}
 		--rq->num;
 	}
 	return 0;
-- 
1.8.1.2

Re: [PATCH net-next 1/2] net: introduce skb_coalesce_rx_frag()

[Kmindg G]

On Thu, Oct 31, 2013 at 6:28 PM, Jason Wang <jasowang@redhat.com> wrote:
> Sometimes we need to coalesce the rx frags to avoid frag list. One example is
> virtio-net driver which tries to use small frags for both MTU sized packet and
> GSO packet. So this patch introduce skb_coalesce_rx_frag() to do this.
>
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Michael Dalton <mwdalton@google.com>
> Cc: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  include/linux/skbuff.h |  3 +++
>  net/core/skbuff.c      | 13 +++++++++++++
>  2 files changed, 16 insertions(+)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 2c15497..e34652b 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -1372,6 +1372,9 @@ static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
>  void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
>                      int size, unsigned int truesize);
>
> +void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int off, int size,
> +                         unsigned int truesize);
> +
>  #define SKB_PAGE_ASSERT(skb)   BUG_ON(skb_shinfo(skb)->nr_frags)
>  #define SKB_FRAG_ASSERT(skb)   BUG_ON(skb_has_frag_list(skb))
>  #define SKB_LINEAR_ASSERT(skb)  BUG_ON(skb_is_nonlinear(skb))
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 0ab32fa..fdef994 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -476,6 +476,19 @@ void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
>  }
>  EXPORT_SYMBOL(skb_add_rx_frag);
>
> +void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int off, int size,
> +                         unsigned int truesize)
> +{
> +       skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
> +
> +       skb_frag_size_add(frag, size);
> +       skb->len += size;
> +       skb->data_len += size;
> +       skb->truesize += truesize;
> +       skb_frag_unref(skb, i);
> +}

I didn't see  you use "off" in skb_coalesce_rx_frag.

> +EXPORT_SYMBOL(skb_coalesce_rx_frag);
> +
>  static void skb_drop_list(struct sk_buff **listp)
>  {
>         kfree_skb_list(*listp);
> --
> 1.8.1.2
>
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH net-next 1/2] net: introduce skb_coalesce_rx_frag()

[Jason Wang]

On 10/31/2013 07:05 PM, Kmindg G wrote:
> On Thu, Oct 31, 2013 at 6:28 PM, Jason Wang <jasowang@redhat.com> wrote:
>> > Sometimes we need to coalesce the rx frags to avoid frag list. One example is
>> > virtio-net driver which tries to use small frags for both MTU sized packet and
>> > GSO packet. So this patch introduce skb_coalesce_rx_frag() to do this.
>> >
>> > Cc: Rusty Russell <rusty@rustcorp.com.au>
>> > Cc: Michael S. Tsirkin <mst@redhat.com>
>> > Cc: Michael Dalton <mwdalton@google.com>
>> > Cc: Eric Dumazet <edumazet@google.com>
>> > Signed-off-by: Jason Wang <jasowang@redhat.com>
>> > ---
>> >  include/linux/skbuff.h |  3 +++
>> >  net/core/skbuff.c      | 13 +++++++++++++
>> >  2 files changed, 16 insertions(+)
>> >
>> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
>> > index 2c15497..e34652b 100644
>> > --- a/include/linux/skbuff.h
>> > +++ b/include/linux/skbuff.h
>> > @@ -1372,6 +1372,9 @@ static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
>> >  void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
>> >                      int size, unsigned int truesize);
>> >
>> > +void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int off, int size,
>> > +                         unsigned int truesize);
>> > +
>> >  #define SKB_PAGE_ASSERT(skb)   BUG_ON(skb_shinfo(skb)->nr_frags)
>> >  #define SKB_FRAG_ASSERT(skb)   BUG_ON(skb_has_frag_list(skb))
>> >  #define SKB_LINEAR_ASSERT(skb)  BUG_ON(skb_is_nonlinear(skb))
>> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
>> > index 0ab32fa..fdef994 100644
>> > --- a/net/core/skbuff.c
>> > +++ b/net/core/skbuff.c
>> > @@ -476,6 +476,19 @@ void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
>> >  }
>> >  EXPORT_SYMBOL(skb_add_rx_frag);
>> >
>> > +void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int off, int size,
>> > +                         unsigned int truesize)
>> > +{
>> > +       skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
>> > +
>> > +       skb_frag_size_add(frag, size);
>> > +       skb->len += size;
>> > +       skb->data_len += size;
>> > +       skb->truesize += truesize;
>> > +       skb_frag_unref(skb, i);
>> > +}
> I didn't see  you use "off" in skb_coalesce_rx_frag.
>

Ture, it's useless. Will post V2.

Thanks

Re: [PATCH net-next 1/2] net: introduce skb_coalesce_rx_frag()

[Michael S. Tsirkin]

On Thu, Oct 31, 2013 at 06:28:32PM +0800, Jason Wang wrote:
> Sometimes we need to coalesce the rx frags to avoid frag list. One example is
> virtio-net driver which tries to use small frags for both MTU sized packet and
> GSO packet. So this patch introduce skb_coalesce_rx_frag() to do this.
> 
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Michael Dalton <mwdalton@google.com>
> Cc: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>


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

> ---
>  include/linux/skbuff.h |  3 +++
>  net/core/skbuff.c      | 13 +++++++++++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 2c15497..e34652b 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -1372,6 +1372,9 @@ static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
>  void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
>  		     int size, unsigned int truesize);
>  
> +void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int off, int size,
> +			  unsigned int truesize);
> +
>  #define SKB_PAGE_ASSERT(skb) 	BUG_ON(skb_shinfo(skb)->nr_frags)
>  #define SKB_FRAG_ASSERT(skb) 	BUG_ON(skb_has_frag_list(skb))
>  #define SKB_LINEAR_ASSERT(skb)  BUG_ON(skb_is_nonlinear(skb))
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 0ab32fa..fdef994 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -476,6 +476,19 @@ void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
>  }
>  EXPORT_SYMBOL(skb_add_rx_frag);
>  
> +void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int off, int size,
> +			  unsigned int truesize)
> +{
> +	skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
> +
> +	skb_frag_size_add(frag, size);
> +	skb->len += size;
> +	skb->data_len += size;
> +	skb->truesize += truesize;
> +	skb_frag_unref(skb, i);
> +}
> +EXPORT_SYMBOL(skb_coalesce_rx_frag);
> +
>  static void skb_drop_list(struct sk_buff **listp)
>  {
>  	kfree_skb_list(*listp);
> -- 
> 1.8.1.2

Re: [PATCH net-next 2/2] virtio-net: coalesce rx frags when possible during rx

[Michael S. Tsirkin]

On Thu, Oct 31, 2013 at 06:28:33PM +0800, Jason Wang wrote:
> Commit 2613af0ed18a11d5c566a81f9a6510b73180660a (virtio_net: migrate mergeable
> rx buffers to page frag allocators) try to increase the payload/truesize for
> MTU-sized traffic. But this will introduce the extra overhead for GSO packets
> received because of the frag list. This commit tries to reduce this issue by
> coalesce the possible rx frags when possible during rx. Test result shows the
> about 15% improvement on full size GSO packet receiving (and even better than
> commit 2613af0ed18a11d5c566a81f9a6510b73180660a).
> 
> Before this commit:
> ./netperf -H 192.168.100.4
> MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.100.4
> () port 0 AF_INET : demo
> Recv   Send    Send
> Socket Socket  Message  Elapsed
> Size   Size    Size     Time     Throughput
> bytes  bytes   bytes    secs.    10^6bits/sec
> 
>  87380  16384  16384    10.00    20303.87
> 
> After this commit:
> ./netperf -H 192.168.100.4
> MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.100.4 () port 0 AF_INET : demo
> Recv   Send    Send
> Socket Socket  Message  Elapsed
> Size   Size    Size     Time     Throughput
> bytes  bytes   bytes    secs.    10^6bits/sec
> 
>  87380  16384  16384    10.00    23841.26
> 
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Michael Dalton <mwdalton@google.com>
> Cc: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>

Good idea.

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

> ---
>  drivers/net/virtio_net.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 113ee93..4ff4f78 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -305,7 +305,7 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *head_skb)
>  	struct sk_buff *curr_skb = head_skb;
>  	char *buf;
>  	struct page *page;
> -	int num_buf, len;
> +	int num_buf, len, offset;
>  
>  	num_buf = hdr->mhdr.num_buffers;
>  	while (--num_buf) {
> @@ -342,9 +342,15 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *head_skb)
>  			head_skb->truesize += MAX_PACKET_LEN;
>  		}
>  		page = virt_to_head_page(buf);
> -		skb_add_rx_frag(curr_skb, num_skb_frags, page,
> -				buf - (char *)page_address(page), len,
> -				MAX_PACKET_LEN);
> +		offset = buf - (char *)page_address(page);
> +		if (skb_can_coalesce(curr_skb, num_skb_frags, page, offset)) {
> +			skb_coalesce_rx_frag(curr_skb, num_skb_frags - 1,
> +					     offset, len, MAX_PACKET_LEN);
> +		} else {
> +			skb_add_rx_frag(curr_skb, num_skb_frags, page,
> +					offset, len,
> +					MAX_PACKET_LEN);
> +		}
>  		--rq->num;
>  	}
>  	return 0;
> -- 
> 1.8.1.2

Re: [PATCH net-next 2/2] virtio-net: coalesce rx frags when possible during rx

[Rusty Russell]

Jason Wang <jasowang@redhat.com> writes:
> Commit 2613af0ed18a11d5c566a81f9a6510b73180660a (virtio_net: migrate mergeable
> rx buffers to page frag allocators) try to increase the payload/truesize for
> MTU-sized traffic. But this will introduce the extra overhead for GSO packets
> received because of the frag list. This commit tries to reduce this issue by
> coalesce the possible rx frags when possible during rx. Test result shows the
> about 15% improvement on full size GSO packet receiving (and even better than
> commit 2613af0ed18a11d5c566a81f9a6510b73180660a).

I don't know about the other users of skb_add_rx_frag, but should
this coalesce-if-possible code be built into that?

Thanks,
Rusty.

Re: [PATCH net-next 2/2] virtio-net: coalesce rx frags when possible during rx

[Jason Wang]

On 11/01/2013 10:13 AM, Rusty Russell wrote:
> Jason Wang <jasowang@redhat.com> writes:
>> Commit 2613af0ed18a11d5c566a81f9a6510b73180660a (virtio_net: migrate mergeable
>> rx buffers to page frag allocators) try to increase the payload/truesize for
>> MTU-sized traffic. But this will introduce the extra overhead for GSO packets
>> received because of the frag list. This commit tries to reduce this issue by
>> coalesce the possible rx frags when possible during rx. Test result shows the
>> about 15% improvement on full size GSO packet receiving (and even better than
>> commit 2613af0ed18a11d5c566a81f9a6510b73180660a).
> I don't know about the other users of skb_add_rx_frag, but should
> this coalesce-if-possible code be built into that?

There're several other users without the possibility check. And Eric
point out in do_tcp_sendpages() skb_add_rx_frag() and skb_can_coalesce()
were used separatedly which can allows us to do some other things in the
middle. So it was ok here.
>
> Thanks,
> Rusty.