Subject: Re: [PATCH net] macvtap: unbreak receiving of gro skb with frag list

From: Jason Wang <[email-masked]>
Date: Mon, 26 Oct 2015 11:15:57 +0800

On 10/23/2015 09:37 PM, Michael S. Tsirkin wrote:
> On Fri, Oct 23, 2015 at 12:57:05AM -0400, Jason Wang wrote:
>> We don't have fraglist support in TAP_FEATURES. This will lead
>> software segmentation of gro skb with frag list. Fixes by having
>> frag list support in TAP_FEATURES.
>>
>> With this patch single session of netperf receiving were restored from
>> about 5Gb/s to about 12Gb/s on mlx4.
>>
>> Fixes a567dd6252 ("macvtap: simplify usage of tap_features")
>> Cc: Vlad Yasevich <[email-masked]>
>> Cc: Michael S. Tsirkin <[email-masked]>
>> Signed-off-by: Jason Wang <[email-masked]>
> Thanks!
> Does this mean we should look at re-adding NETIF_F_FRAGLIST
> to virtio-net as well?

Not sure I get the point, but probably not. This is for receiving and
skb_copy_datagram_iter() can deal with frag list.

>
>> ---
>>  drivers/net/macvtap.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
>> index 248478c..197c939 100644
>> --- a/drivers/net/macvtap.c
>> +++ b/drivers/net/macvtap.c
>> @@ -137,7 +137,7 @@ static const struct proto_ops macvtap_socket_ops;
>>  #define TUN_OFFLOADS (NETIF_F_HW_CSUM | NETIF_F_TSO_ECN | NETIF_F_TSO | \
>>  		      NETIF_F_TSO6 | NETIF_F_UFO)
>>  #define RX_OFFLOADS (NETIF_F_GRO | NETIF_F_LRO)
>> -#define TAP_FEATURES (NETIF_F_GSO | NETIF_F_SG)
>> +#define TAP_FEATURES (NETIF_F_GSO | NETIF_F_SG | NETIF_F_FRAGLIST)
>>  
>>  static struct macvlan_dev *macvtap_get_vlan_rcu(const struct net_device *dev)
>>  {
>> -- 
>> 1.8.3.1
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