Re: [dpdk-dev] [PATCH v2 0/4] Introduce IF proxy library

[Thomas Monjalon <thomas@monjalon.net>]

04/04/2020 20:30, Andrzej Ostruszka [C]:
> Thomas,
> 
> I have replied to the other mail, here I just want to confirm, that I'm
> fine with the proposed "general messaging" which other libraries (IF
> Proxy including) could utilize.
> 
> See also below.
> 
> On 4/3/20 7:19 PM, Thomas Monjalon wrote:
> > 02/04/2020 15:48, Andrzej Ostruszka [C]:
> >> On 3/26/20 6:42 PM, Andrzej Ostruszka wrote:
> [...]
> >> Would that be easier/better to register queue together with a bitmask of
> >> event types that given queue is accepting?  Than during setup phase
> >> application would select just one queue to handle "global" events and
> >> the logic of event handling for lcores should be simplier.
> >>
> >> Let me know what you think.
> > 
> > I think we want to avoid complicate design.
> > So let's choose between callback and message queue.
> > I vote for message queue because it can handle any situation,
> > and it allows to control the context of the event processing.
> > The other reason is that I believe we need message queueing for
> > other purposes in DPDK (ex: multi-process, telemetry).
> > 
> > You start thinking about complex message management.
> > And I start thinking about other usages of message queueing.
> > So I think it is the right time to introduce a generic messaging in DPDK.
> > Note: the IPC rte_mp should be built on top of such generic messaging.
> 
> Do you have also inter-lcore communication in mind here?  Or just
> "external" world to "some DPDK controller/dispatcher" and how that is
> passed to other cores is an application writer problem.

I was thinking at communication with:
	- DPDK event from random context
	- secondary process
	- external application
	- remote application

In all cases, I thought the message receiver would be the master core.
But you are probably right that targeting a specific core may be
interesting.

> > If you agree, we can start a new email thread to better discuss
> > the generic messaging sub-system.
> 
> Yes, lets talk about that.

Let's start with the requirements (as above).
I'll write such email soon.


> > I describe here the 3 properties I have in mind:
> > 
> > 1/ Message policy
> > One very important rule in DPDK is to let the control to the application.
> > So the messaging policy must be managed by the application via DPDK API.
> > 
> > 2/ Message queue
> > It seems we should rely on ZeroMQ. Here is why:
> > http://zguide.zeromq.org/page:all#Why-We-Needed-ZeroMQ
> > 
> > 3/ Message format
> > I am not sure whether we can manage with "simple strings", TLV,
> > or should we use something more complex like protobuf?