[PATCH 1/5] VSOCK: support fill mergeable rx buffer in guest

[PATCH 1/5] VSOCK: support fill mergeable rx buffer in guest

[jiangyiwen]

In driver probing, if virtio has VIRTIO_VSOCK_F_MRG_RXBUF feature,
it will fill mergeable rx buffer, support for host send mergeable
rx buffer. It will fill a page everytime to compact with small
packet and big packet.

Signed-off-by: Yiwen Jiang <jiangyiwen@huawei.com>
---
 include/linux/virtio_vsock.h     |  3 ++
 net/vmw_vsock/virtio_transport.c | 72 +++++++++++++++++++++++++++++-----------
 2 files changed, 56 insertions(+), 19 deletions(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index e223e26..bf84418 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -14,6 +14,9 @@
 #define VIRTIO_VSOCK_MAX_BUF_SIZE		0xFFFFFFFFUL
 #define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE		(1024 * 64)

+/* Virtio-vsock feature */
+#define VIRTIO_VSOCK_F_MRG_RXBUF 0 /* Host can merge receive buffers. */
+
 enum {
 	VSOCK_VQ_RX     = 0, /* for host to guest data */
 	VSOCK_VQ_TX     = 1, /* for guest to host data */
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index 5d3cce9..2040a9e 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -64,6 +64,7 @@ struct virtio_vsock {
 	struct virtio_vsock_event event_list[8];

 	u32 guest_cid;
+	bool mergeable;
 };

 static struct virtio_vsock *virtio_vsock_get(void)
@@ -256,6 +257,25 @@ static int virtio_transport_send_pkt_loopback(struct virtio_vsock *vsock,
 	return 0;
 }

+static int fill_mergeable_rx_buff(struct virtqueue *vq)
+{
+	void *page = NULL;
+	struct scatterlist sg;
+	int err;
+
+	page = (void *)get_zeroed_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	sg_init_one(&sg, page, PAGE_SIZE);
+
+	err = virtqueue_add_inbuf(vq, &sg, 1, page, GFP_KERNEL);
+	if (err < 0)
+		free_page((unsigned long) page);
+
+	return err;
+}
+
 static void virtio_vsock_rx_fill(struct virtio_vsock *vsock)
 {
 	int buf_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE;
@@ -267,27 +287,33 @@ static void virtio_vsock_rx_fill(struct virtio_vsock *vsock)
 	vq = vsock->vqs[VSOCK_VQ_RX];

 	do {
-		pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
-		if (!pkt)
-			break;
+		if (vsock->mergeable) {
+			ret = fill_mergeable_rx_buff(vq);
+			if (ret)
+				break;
+		} else {
+			pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
+			if (!pkt)
+				break;

-		pkt->buf = kmalloc(buf_len, GFP_KERNEL);
-		if (!pkt->buf) {
-			virtio_transport_free_pkt(pkt);
-			break;
-		}
+			pkt->buf = kmalloc(buf_len, GFP_KERNEL);
+			if (!pkt->buf) {
+				virtio_transport_free_pkt(pkt);
+				break;
+			}

-		pkt->len = buf_len;
+			pkt->len = buf_len;

-		sg_init_one(&hdr, &pkt->hdr, sizeof(pkt->hdr));
-		sgs[0] = &hdr;
+			sg_init_one(&hdr, &pkt->hdr, sizeof(pkt->hdr));
+			sgs[0] = &hdr;

-		sg_init_one(&buf, pkt->buf, buf_len);
-		sgs[1] = &buf;
-		ret = virtqueue_add_sgs(vq, sgs, 0, 2, pkt, GFP_KERNEL);
-		if (ret) {
-			virtio_transport_free_pkt(pkt);
-			break;
+			sg_init_one(&buf, pkt->buf, buf_len);
+			sgs[1] = &buf;
+			ret = virtqueue_add_sgs(vq, sgs, 0, 2, pkt, GFP_KERNEL);
+			if (ret) {
+				virtio_transport_free_pkt(pkt);
+				break;
+			}
 		}
 		vsock->rx_buf_nr++;
 	} while (vq->num_free);
@@ -588,6 +614,9 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
 	if (ret < 0)
 		goto out_vqs;

+	if (virtio_has_feature(vdev, VIRTIO_VSOCK_F_MRG_RXBUF))
+		vsock->mergeable = true;
+
 	vsock->rx_buf_nr = 0;
 	vsock->rx_buf_max_nr = 0;
 	atomic_set(&vsock->queued_replies, 0);
@@ -640,8 +669,12 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
 	vdev->config->reset(vdev);

 	mutex_lock(&vsock->rx_lock);
-	while ((pkt = virtqueue_detach_unused_buf(vsock->vqs[VSOCK_VQ_RX])))
-		virtio_transport_free_pkt(pkt);
+	while ((pkt = virtqueue_detach_unused_buf(vsock->vqs[VSOCK_VQ_RX]))) {
+		if (vsock->mergeable)
+			free_page((unsigned long)(void *)pkt);
+		else
+			virtio_transport_free_pkt(pkt);
+	}
 	mutex_unlock(&vsock->rx_lock);

 	mutex_lock(&vsock->tx_lock);
@@ -683,6 +716,7 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
 };

 static unsigned int features[] = {
+	VIRTIO_VSOCK_F_MRG_RXBUF,
 };

 static struct virtio_driver virtio_vsock_driver = {
-- 
1.8.3.1

Re: [PATCH 1/5] VSOCK: support fill mergeable rx buffer in guest

[Jason Wang]

On 2018/11/5 下午3:45, jiangyiwen wrote:
> In driver probing, if virtio has VIRTIO_VSOCK_F_MRG_RXBUF feature,
> it will fill mergeable rx buffer, support for host send mergeable
> rx buffer. It will fill a page everytime to compact with small
> packet and big packet.
>
> Signed-off-by: Yiwen Jiang <jiangyiwen@huawei.com>
> ---
>   include/linux/virtio_vsock.h     |  3 ++
>   net/vmw_vsock/virtio_transport.c | 72 +++++++++++++++++++++++++++++-----------
>   2 files changed, 56 insertions(+), 19 deletions(-)
>
> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> index e223e26..bf84418 100644
> --- a/include/linux/virtio_vsock.h
> +++ b/include/linux/virtio_vsock.h
> @@ -14,6 +14,9 @@
>   #define VIRTIO_VSOCK_MAX_BUF_SIZE		0xFFFFFFFFUL
>   #define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE		(1024 * 64)
>
> +/* Virtio-vsock feature */
> +#define VIRTIO_VSOCK_F_MRG_RXBUF 0 /* Host can merge receive buffers. */
> +
>   enum {
>   	VSOCK_VQ_RX     = 0, /* for host to guest data */
>   	VSOCK_VQ_TX     = 1, /* for guest to host data */
> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
> index 5d3cce9..2040a9e 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -64,6 +64,7 @@ struct virtio_vsock {
>   	struct virtio_vsock_event event_list[8];
>
>   	u32 guest_cid;
> +	bool mergeable;
>   };
>
>   static struct virtio_vsock *virtio_vsock_get(void)
> @@ -256,6 +257,25 @@ static int virtio_transport_send_pkt_loopback(struct virtio_vsock *vsock,
>   	return 0;
>   }
>
> +static int fill_mergeable_rx_buff(struct virtqueue *vq)
> +{
> +	void *page = NULL;
> +	struct scatterlist sg;
> +	int err;
> +
> +	page = (void *)get_zeroed_page(GFP_KERNEL);


Any reason to use zeroed page?


> +	if (!page)
> +		return -ENOMEM;
> +
> +	sg_init_one(&sg, page, PAGE_SIZE);


FYI, for virtio-net we have several optimizations for mergeable rx buffer:

- skb_page_frag_refill() which can use high order page and reduce the 
stress of page allocator

- we don't use fixed buffer size, instead we use EWMA to estimate the 
possible rx buffer size to avoid internal fragmentation


If we can try to reuse virtio-net driver, we will get those nice features.


Thanks


> +
> +	err = virtqueue_add_inbuf(vq, &sg, 1, page, GFP_KERNEL);
> +	if (err < 0)
> +		free_page((unsigned long) page);
> +
> +	return err;
> +}
> +
>   static void virtio_vsock_rx_fill(struct virtio_vsock *vsock)
>   {
>   	int buf_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE;
> @@ -267,27 +287,33 @@ static void virtio_vsock_rx_fill(struct virtio_vsock *vsock)
>   	vq = vsock->vqs[VSOCK_VQ_RX];
>
>   	do {
> -		pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
> -		if (!pkt)
> -			break;
> +		if (vsock->mergeable) {
> +			ret = fill_mergeable_rx_buff(vq);
> +			if (ret)
> +				break;
> +		} else {
> +			pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
> +			if (!pkt)
> +				break;
>
> -		pkt->buf = kmalloc(buf_len, GFP_KERNEL);
> -		if (!pkt->buf) {
> -			virtio_transport_free_pkt(pkt);
> -			break;
> -		}
> +			pkt->buf = kmalloc(buf_len, GFP_KERNEL);
> +			if (!pkt->buf) {
> +				virtio_transport_free_pkt(pkt);
> +				break;
> +			}
>
> -		pkt->len = buf_len;
> +			pkt->len = buf_len;
>
> -		sg_init_one(&hdr, &pkt->hdr, sizeof(pkt->hdr));
> -		sgs[0] = &hdr;
> +			sg_init_one(&hdr, &pkt->hdr, sizeof(pkt->hdr));
> +			sgs[0] = &hdr;
>
> -		sg_init_one(&buf, pkt->buf, buf_len);
> -		sgs[1] = &buf;
> -		ret = virtqueue_add_sgs(vq, sgs, 0, 2, pkt, GFP_KERNEL);
> -		if (ret) {
> -			virtio_transport_free_pkt(pkt);
> -			break;
> +			sg_init_one(&buf, pkt->buf, buf_len);
> +			sgs[1] = &buf;
> +			ret = virtqueue_add_sgs(vq, sgs, 0, 2, pkt, GFP_KERNEL);
> +			if (ret) {
> +				virtio_transport_free_pkt(pkt);
> +				break;
> +			}
>   		}
>   		vsock->rx_buf_nr++;
>   	} while (vq->num_free);
> @@ -588,6 +614,9 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
>   	if (ret < 0)
>   		goto out_vqs;
>
> +	if (virtio_has_feature(vdev, VIRTIO_VSOCK_F_MRG_RXBUF))
> +		vsock->mergeable = true;
> +
>   	vsock->rx_buf_nr = 0;
>   	vsock->rx_buf_max_nr = 0;
>   	atomic_set(&vsock->queued_replies, 0);
> @@ -640,8 +669,12 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
>   	vdev->config->reset(vdev);
>
>   	mutex_lock(&vsock->rx_lock);
> -	while ((pkt = virtqueue_detach_unused_buf(vsock->vqs[VSOCK_VQ_RX])))
> -		virtio_transport_free_pkt(pkt);
> +	while ((pkt = virtqueue_detach_unused_buf(vsock->vqs[VSOCK_VQ_RX]))) {
> +		if (vsock->mergeable)
> +			free_page((unsigned long)(void *)pkt);
> +		else
> +			virtio_transport_free_pkt(pkt);
> +	}
>   	mutex_unlock(&vsock->rx_lock);
>
>   	mutex_lock(&vsock->tx_lock);
> @@ -683,6 +716,7 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
>   };
>
>   static unsigned int features[] = {
> +	VIRTIO_VSOCK_F_MRG_RXBUF,
>   };
>
>   static struct virtio_driver virtio_vsock_driver = {

Re: [PATCH 1/5] VSOCK: support fill mergeable rx buffer in guest

[jiangyiwen]

On 2018/11/6 11:38, Jason Wang wrote:
> 
> On 2018/11/5 下午3:45, jiangyiwen wrote:
>> In driver probing, if virtio has VIRTIO_VSOCK_F_MRG_RXBUF feature,
>> it will fill mergeable rx buffer, support for host send mergeable
>> rx buffer. It will fill a page everytime to compact with small
>> packet and big packet.
>>
>> Signed-off-by: Yiwen Jiang <jiangyiwen@huawei.com>
>> ---
>>   include/linux/virtio_vsock.h     |  3 ++
>>   net/vmw_vsock/virtio_transport.c | 72 +++++++++++++++++++++++++++++-----------
>>   2 files changed, 56 insertions(+), 19 deletions(-)
>>
>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>> index e223e26..bf84418 100644
>> --- a/include/linux/virtio_vsock.h
>> +++ b/include/linux/virtio_vsock.h
>> @@ -14,6 +14,9 @@
>>   #define VIRTIO_VSOCK_MAX_BUF_SIZE        0xFFFFFFFFUL
>>   #define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE        (1024 * 64)
>>
>> +/* Virtio-vsock feature */
>> +#define VIRTIO_VSOCK_F_MRG_RXBUF 0 /* Host can merge receive buffers. */
>> +
>>   enum {
>>       VSOCK_VQ_RX     = 0, /* for host to guest data */
>>       VSOCK_VQ_TX     = 1, /* for guest to host data */
>> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>> index 5d3cce9..2040a9e 100644
>> --- a/net/vmw_vsock/virtio_transport.c
>> +++ b/net/vmw_vsock/virtio_transport.c
>> @@ -64,6 +64,7 @@ struct virtio_vsock {
>>       struct virtio_vsock_event event_list[8];
>>
>>       u32 guest_cid;
>> +    bool mergeable;
>>   };
>>
>>   static struct virtio_vsock *virtio_vsock_get(void)
>> @@ -256,6 +257,25 @@ static int virtio_transport_send_pkt_loopback(struct virtio_vsock *vsock,
>>       return 0;
>>   }
>>
>> +static int fill_mergeable_rx_buff(struct virtqueue *vq)
>> +{
>> +    void *page = NULL;
>> +    struct scatterlist sg;
>> +    int err;
>> +
>> +    page = (void *)get_zeroed_page(GFP_KERNEL);
> 
> 
> Any reason to use zeroed page?

In previous version, the entire structure of virtio_vsock_pkt is preallocated
in guest use kzalloc, it is a contiguous zeroed physical memory, but host only
need to fill virtio_vsock_hdr size.

However, in mergeable rx buffer version, we only fill a page in vring descriptor
in guest, and I will reserve size of virtio_vsock_pkt in host instead of write
the total size of virtio_vsock_pkt, for the correctness of structure value,
we should set zeroed page in advance.

> 
> 
>> +    if (!page)
>> +        return -ENOMEM;
>> +
>> +    sg_init_one(&sg, page, PAGE_SIZE);
> 
> 
> FYI, for virtio-net we have several optimizations for mergeable rx buffer:
> 
> - skb_page_frag_refill() which can use high order page and reduce the stress of page allocator
> 

You're right, initially I want to use a memory poll to manage the rx buffer,
and then use this in the later optimized patch. Your advice is very great.

> - we don't use fixed buffer size, instead we use EWMA to estimate the possible rx buffer size to avoid internal fragmentation
> 

Ok, I analysis the feature and consider add it into my patches.

> 
> If we can try to reuse virtio-net driver, we will get those nice features.
> 

Yes, after all virtio-net has a very good ecological environment, and it also
do many performance optimization, it is actually a good idea.

> 
> Thanks
> 
> 
>> +
>> +    err = virtqueue_add_inbuf(vq, &sg, 1, page, GFP_KERNEL);
>> +    if (err < 0)
>> +        free_page((unsigned long) page);
>> +
>> +    return err;
>> +}
>> +
>>   static void virtio_vsock_rx_fill(struct virtio_vsock *vsock)
>>   {
>>       int buf_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE;
>> @@ -267,27 +287,33 @@ static void virtio_vsock_rx_fill(struct virtio_vsock *vsock)
>>       vq = vsock->vqs[VSOCK_VQ_RX];
>>
>>       do {
>> -        pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
>> -        if (!pkt)
>> -            break;
>> +        if (vsock->mergeable) {
>> +            ret = fill_mergeable_rx_buff(vq);
>> +            if (ret)
>> +                break;
>> +        } else {
>> +            pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
>> +            if (!pkt)
>> +                break;
>>
>> -        pkt->buf = kmalloc(buf_len, GFP_KERNEL);
>> -        if (!pkt->buf) {
>> -            virtio_transport_free_pkt(pkt);
>> -            break;
>> -        }
>> +            pkt->buf = kmalloc(buf_len, GFP_KERNEL);
>> +            if (!pkt->buf) {
>> +                virtio_transport_free_pkt(pkt);
>> +                break;
>> +            }
>>
>> -        pkt->len = buf_len;
>> +            pkt->len = buf_len;
>>
>> -        sg_init_one(&hdr, &pkt->hdr, sizeof(pkt->hdr));
>> -        sgs[0] = &hdr;
>> +            sg_init_one(&hdr, &pkt->hdr, sizeof(pkt->hdr));
>> +            sgs[0] = &hdr;
>>
>> -        sg_init_one(&buf, pkt->buf, buf_len);
>> -        sgs[1] = &buf;
>> -        ret = virtqueue_add_sgs(vq, sgs, 0, 2, pkt, GFP_KERNEL);
>> -        if (ret) {
>> -            virtio_transport_free_pkt(pkt);
>> -            break;
>> +            sg_init_one(&buf, pkt->buf, buf_len);
>> +            sgs[1] = &buf;
>> +            ret = virtqueue_add_sgs(vq, sgs, 0, 2, pkt, GFP_KERNEL);
>> +            if (ret) {
>> +                virtio_transport_free_pkt(pkt);
>> +                break;
>> +            }
>>           }
>>           vsock->rx_buf_nr++;
>>       } while (vq->num_free);
>> @@ -588,6 +614,9 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
>>       if (ret < 0)
>>           goto out_vqs;
>>
>> +    if (virtio_has_feature(vdev, VIRTIO_VSOCK_F_MRG_RXBUF))
>> +        vsock->mergeable = true;
>> +
>>       vsock->rx_buf_nr = 0;
>>       vsock->rx_buf_max_nr = 0;
>>       atomic_set(&vsock->queued_replies, 0);
>> @@ -640,8 +669,12 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
>>       vdev->config->reset(vdev);
>>
>>       mutex_lock(&vsock->rx_lock);
>> -    while ((pkt = virtqueue_detach_unused_buf(vsock->vqs[VSOCK_VQ_RX])))
>> -        virtio_transport_free_pkt(pkt);
>> +    while ((pkt = virtqueue_detach_unused_buf(vsock->vqs[VSOCK_VQ_RX]))) {
>> +        if (vsock->mergeable)
>> +            free_page((unsigned long)(void *)pkt);
>> +        else
>> +            virtio_transport_free_pkt(pkt);
>> +    }
>>       mutex_unlock(&vsock->rx_lock);
>>
>>       mutex_lock(&vsock->tx_lock);
>> @@ -683,6 +716,7 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
>>   };
>>
>>   static unsigned int features[] = {
>> +    VIRTIO_VSOCK_F_MRG_RXBUF,
>>   };
>>
>>   static struct virtio_driver virtio_vsock_driver = {
> 
> .
> 


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Re: [PATCH 1/5] VSOCK: support fill mergeable rx buffer in guest

[Jason Wang]

On 2018/11/6 下午2:22, jiangyiwen wrote:
> On 2018/11/6 11:38, Jason Wang wrote:
>> On 2018/11/5 下午3:45, jiangyiwen wrote:
>>> In driver probing, if virtio has VIRTIO_VSOCK_F_MRG_RXBUF feature,
>>> it will fill mergeable rx buffer, support for host send mergeable
>>> rx buffer. It will fill a page everytime to compact with small
>>> packet and big packet.
>>>
>>> Signed-off-by: Yiwen Jiang<jiangyiwen@huawei.com>
>>> ---
>>>    include/linux/virtio_vsock.h     |  3 ++
>>>    net/vmw_vsock/virtio_transport.c | 72 +++++++++++++++++++++++++++++-----------
>>>    2 files changed, 56 insertions(+), 19 deletions(-)
>>>
>>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>>> index e223e26..bf84418 100644
>>> --- a/include/linux/virtio_vsock.h
>>> +++ b/include/linux/virtio_vsock.h
>>> @@ -14,6 +14,9 @@
>>>    #define VIRTIO_VSOCK_MAX_BUF_SIZE        0xFFFFFFFFUL
>>>    #define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE        (1024 * 64)
>>>
>>> +/* Virtio-vsock feature */
>>> +#define VIRTIO_VSOCK_F_MRG_RXBUF 0 /* Host can merge receive buffers. */
>>> +
>>>    enum {
>>>        VSOCK_VQ_RX     = 0, /* for host to guest data */
>>>        VSOCK_VQ_TX     = 1, /* for guest to host data */
>>> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>>> index 5d3cce9..2040a9e 100644
>>> --- a/net/vmw_vsock/virtio_transport.c
>>> +++ b/net/vmw_vsock/virtio_transport.c
>>> @@ -64,6 +64,7 @@ struct virtio_vsock {
>>>        struct virtio_vsock_event event_list[8];
>>>
>>>        u32 guest_cid;
>>> +    bool mergeable;
>>>    };
>>>
>>>    static struct virtio_vsock *virtio_vsock_get(void)
>>> @@ -256,6 +257,25 @@ static int virtio_transport_send_pkt_loopback(struct virtio_vsock *vsock,
>>>        return 0;
>>>    }
>>>
>>> +static int fill_mergeable_rx_buff(struct virtqueue *vq)
>>> +{
>>> +    void *page = NULL;
>>> +    struct scatterlist sg;
>>> +    int err;
>>> +
>>> +    page = (void *)get_zeroed_page(GFP_KERNEL);
>> Any reason to use zeroed page?
> In previous version, the entire structure of virtio_vsock_pkt is preallocated
> in guest use kzalloc, it is a contiguous zeroed physical memory, but host only
> need to fill virtio_vsock_hdr size.
>
> However, in mergeable rx buffer version, we only fill a page in vring descriptor
> in guest, and I will reserve size of virtio_vsock_pkt in host instead of write
> the total size of virtio_vsock_pkt, for the correctness of structure value,
> we should set zeroed page in advance.


I may miss something, but it looks to me only the header needs to be zeroed.


>
>>> +    if (!page)
>>> +        return -ENOMEM;
>>> +
>>> +    sg_init_one(&sg, page, PAGE_SIZE);
>> FYI, for virtio-net we have several optimizations for mergeable rx buffer:
>>
>> - skb_page_frag_refill() which can use high order page and reduce the stress of page allocator
>>
> You're right, initially I want to use a memory poll to manage the rx buffer,
> and then use this in the later optimized patch. Your advice is very great.
>
>> - we don't use fixed buffer size, instead we use EWMA to estimate the possible rx buffer size to avoid internal fragmentation
>>
> Ok, I analysis the feature and consider add it into my patches.
>
>> If we can try to reuse virtio-net driver, we will get those nice features.
>>
> Yes, after all virtio-net has a very good ecological environment, and it also
> do many performance optimization, it is actually a good idea.
>

Yes, so my suggestion is to consider to reuse them (unless we found 
something that is a real blocker) instead of duplicating codes, features 
a bugs.

Thanks