[ovs-dev] [patch net-next RFC 10/12] openvswitch: add support for datapath hardware offload

[Jiri Pirko]

Thu, Sep 04, 2014 at 11:03:46AM CEST, simon.horman at netronome.com wrote:
>On Sat, Aug 23, 2014 at 10:09:13AM -0700, John Fastabend wrote:
>>On 08/23/2014 07:51 AM, Thomas Graf wrote:
>>>On 08/23/14 at 11:24am, Jiri Pirko wrote:
>>>>Sat, Aug 23, 2014 at 12:53:34AM CEST, sfeldma at cumulusnetworks.com wrote:
>>>>>
>>>>>On Aug 22, 2014, at 12:39 PM, John Fastabend <john.fastabend at gmail.com> wrote:
>
>[snip]
>
>>>>>>- Also there is no programmatic way to learn which flows are
>>>>>>   in hardware and which in software. There is a pr_warn but
>>>>>>   that doesn't help when interacting with the hardware remotely.
>>>>>>   I need some mechanism to dump the set of hardware tables and
>>>>>>   the set of software tables.
>>>>>
>>>>>Agreed, we need a way to annotate which flows are installed hardware.
>>>>
>>>>Yes, we discussed that already. We need to make OVS daemon hw-offload
>>>>aware indicating which flow it want/prefers to be offloaded. This is I
>>>>believe easily extentable feature and can be added whenever the right
>>>>time is.
>>>
>>>I think the swdev flow API is good as-is. The bitmask specyfing the
>>>offload preference with all the granularity (offload-or-fail,
>>>try-to-offload, never-offload) needed can be added later, either in
>>>OVS only or in swdev itself.
>>>
>>>What is unclear in this patch is how OVS user space can know which
>>>flows are offloaded and which aren't. A status field would help here
>>>which indicates either: flow inserted and offloaded, flow inserted but
>>>not offloaded. Given that, the API consumer can easily keep track of
>>>which flows are currently offloaded.
>>>
>>
>>Right. I think this is basically what Jiri and I discussed when he
>>originally posted the series. For my use cases this is one of the
>>more interesting pieces. If no one else is looking at it I can try
>>it on some of the already existing open source drivers that have some
>>very simple support for ingress flow tables read flow director.
>
>While I agree that it would be good to have such controls I'd like
>to take a small step back as I'm not entirely clear how flow deletion
>works in the current code. I am specifically refering to the Open vSwitch
>use-case.
>
>My assumption is that if a flow is offloaded then once it is set up in
>hardware packets won't hit the datapath any more.  However, statistics need
>to be updated in the datapath for active flows otherwise they will be
>evicted by ovs-vswtichd.

Yes, that is exactly what happens.

>
>In short, I was expecting to see get and statistics callbacks.

We plan to implement this in rocker device as one of next steps.


>
>[snip]