Re: [RFC PATCH 00/10] Device Memory TCP

[David Ahern]

On 7/18/23 12:29 PM, Jakub Kicinski wrote:
> On Tue, 18 Jul 2023 12:20:59 -0600 David Ahern wrote:
>> On 7/18/23 12:15 PM, Jakub Kicinski wrote:
>>> On Tue, 18 Jul 2023 15:06:29 -0300 Jason Gunthorpe wrote:  
>>>> netlink feels like a weird API choice for that, in particular it would
>>>> be really wrong to somehow bind the lifecycle of a netlink object to a
>>>> process.  
>>>
>>> Netlink is the right API, life cycle of objects can be easily tied to
>>> a netlink socket.  
>>
>> That is an untuitive connection -- memory references, h/w queues, flow
>> steering should be tied to the datapath socket, not a control plane socket.
> 
> There's one RSS context for may datapath sockets. Plus a lot of the
> APIs already exist, and it's more of a question of packaging them up 
> at the user space level. For things which do not have an API, however,
> netlink, please.

I do not see how 1 RSS context (or more specifically a h/w Rx queue) can
be used properly with memory from different processes (or dma-buf
references). When the process dies, that memory needs to be flushed from
the H/W queues. Queues with interlaced submissions make that more
complicated.

I guess the devil is in the details; I look forward to the evolution of
the patches.