[dpdk-dev] [RFC v2 3/5] ether: Add flow timeout support

[Alex Rosenbaum]

On Fri, Dec 22, 2017 at 11:03 AM, Zhang, Qi Z <qi.z.zhang at intel.com> wrote:
>> On Thu, Dec 21, 2017 at 4:35 AM, Qi Zhang <qi.z.zhang at intel.com> wrote:
>> > Add new APIs to support flow timeout, application is able to 1. Setup
>> > the time duration of a flow, the flow is expected to be deleted
>> > automatically when timeout.
>>
>> Can you explain how the application (OVS) is expected to use this API?
>> It will help to better understand the motivation here...
>
> I think the purpose of the APIs is to expose the hardware feature that support
> flow auto delete with a timeout.
> As I know, for OVS, every flow in flow table will have time duration
> A flow be offloaded to hardware is still required to be deleted in specific time,
> I think these APIs help OVS to take advantage HW feature and simplify the flow
> aging management

Are you sure this will allow OVS to 'fire-and-forget' about the rule removal?
or will OVS anyway do rule cleanup from application tables?

Do you know if OVS flow timers are (or can be) re-armed in different
use cases? e.g. extending the timeout duration if traffic is still
flowing?



>> Are you trying to move the aging timer from application code into the PMD?
>> or can your HW remove/disable/inactivate a flow at certain time semantics
>> without software context?
>
> Yes, it for hardware feature.

So if the hardware auto removes the hardware steering entry, what
software part deletes the rte_flow handle?
What software part triggers the application callback? from what
context? will locks be required?

How do you prevent races between application thread and the context
deleting/accessing the rte_flow handle?
I mean in cases that application wants to delete the flow before the
timeout expires, but actually it is same time hardware deletes it.

Alex