[ovs-dev] [PATCH v7] datapath: Add Stateless TCP Tunneling protocol.

Pravin Shelar pshelar at nicira.com
Fri Apr 24 18:25:29 UTC 2015


On Thu, Apr 23, 2015 at 12:11 PM, Pravin Shelar <pshelar at nicira.com> wrote:
> On Thu, Apr 23, 2015 at 11:55 AM, Jesse Gross <jesse at nicira.com> wrote:
>
>> I'm a little nervous about orphaning the packets in this case since it
>> can potentially affect socket accounting and from a high level,
>> there's no logical reason to do so (i.e. we're not crossing a boundary
>> or something like that).
>>
>> I guess that in many cases (particularly on the transmit side), moving
>> the truesize around in normalize_frag_list() and skb_try_coalesce()
>> will effectively cancel each other out if we can merge things together
>> (although I guess that depends on the source of the frag_list, IP
>> fragment reassembly first tries to coalesce and then falls back on
>> creating frag_lists, in which case us trying to merge things is a
>> waste of time). It would be nice if we could relegate this to a corner
>> case and just linearize in those situations. Or better yet, more
>> deeply understand the conditions where we get the frag_list on
>> transmit and see if it's really worth trying to coalesce them at all.
>> grepping drivers/net I don't see a lot of frag_list creation. Even on
>> receive, I'm not totally sure that breaking up frag_lists makes sense
>> if skb_segment() can handle it now...
>
> Lat time I looked into it it could not handle uneven geometry of skb
> that STT generate. I will recheck it.

I checked with or without STT segmenting the skb and saw 12%
performance improvement with STT segmentation compared to
skb_segment(). This is with ixgbe driver generating skbs with
fraglist.



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