[ovs-dev] [PATCH v2] datapath: Remove tunnel header caching.

[Pravin Shelar]

On Fri, Oct 26, 2012 at 5:15 PM, Jesse Gross <jesse at nicira.com> wrote:
> On Thu, Oct 25, 2012 at 11:14 AM, Pravin B Shelar <pshelar at nicira.com> wrote:
>> Tunnel caching was added to reduce CPU utilization on TX path
>> by caching packet header, So performance gain is directly proportional
>> to number of skbs transferred. But with help of offloads skb are getting
>> larger. So there are less number of skbs. Therefore header caching does
>> not shows similar gains we seen in past. And now kernel 3.6 has removed
>> dst caching from networking which makes header caching even more tricky.
>> So this commit removes header caching from OVS tunnelling.
>>
>> Signed-off-by: Pravin B Shelar <pshelar at nicira.com>
>
> We should probably add a NEWS item.
OK.

>
>> diff --git a/datapath/tunnel.h b/datapath/tunnel.h
>> index 951a6f1..f296ecb 100644
>> --- a/datapath/tunnel.h
>> +++ b/datapath/tunnel.h
>> -       /*
>> -        * Updates the cached header of a packet to match the actual packet
>> +        * Updates the header of a packet to match the actual packet
>>          * data.  Typical things that might need to be updated are length,
>>          * checksum, etc.  The IP header will have already been updated and this
>>          * is the final step before transmission.  Returns a linked list of
>
> Is this still really updating the header now?  It's really creating it
> from scratch.
>
right. I will rename it back to build_header.

>> diff --git a/datapath/vport-gre.c b/datapath/vport-gre.c
>> index d02d4ec..3a877f3 100644
>> --- a/datapath/vport-gre.c
>> +++ b/datapath/vport-gre.c
>> @@ -196,7 +162,6 @@ static struct sk_buff *gre_update_header(const struct vport *vport,
>>          * packet originally had DF set.
>>          */
>>         skb->local_df = 1;
>> -       __ip_select_ident(ip_hdr(skb), dst, 0);
>
> Why is this no longer needed?

right, It is required.