[dpdk-dev] [PATCH] gpudev: introduce memory API

[Thomas Monjalon]

04/06/2021 17:20, Jerin Jacob:
> On Fri, Jun 4, 2021 at 7:39 PM Thomas Monjalon <thomas at monjalon.net> wrote:
> > 04/06/2021 15:59, Andrew Rybchenko:
> > > On 6/4/21 4:18 PM, Thomas Monjalon wrote:
> > > > 04/06/2021 15:05, Andrew Rybchenko:
> > > >> On 6/4/21 3:46 PM, Thomas Monjalon wrote:
> > > >>> 04/06/2021 13:09, Jerin Jacob:
> > > >>>> On Fri, Jun 4, 2021 at 3:58 PM Thomas Monjalon <thomas at monjalon.net> wrote:
> > > >>>>> 03/06/2021 11:33, Ferruh Yigit:
> > > >>>>>> On 6/3/2021 8:47 AM, Jerin Jacob wrote:
> > > >>>>>>> On Thu, Jun 3, 2021 at 2:05 AM Thomas Monjalon <thomas at monjalon.net> wrote:
> > > >>>>>>>> +  [gpudev]             (@ref rte_gpudev.h),
> > > >>>>>>>
> > > >>>>>>> Since this device does not have a queue etc? Shouldn't make it a
> > > >>>>>>> library like mempool with vendor-defined ops?
> > > >>>>>>
> > > >>>>>> +1
> > > >>>>>>
> > > >>>>>> Current RFC announces additional memory allocation capabilities, which can suits
> > > >>>>>> better as extension to existing memory related library instead of a new device
> > > >>>>>> abstraction library.
> > > >>>>>
> > > >>>>> It is not replacing mempool.
> > > >>>>> It is more at the same level as EAL memory management:
> > > >>>>> allocate simple buffer, but with the exception it is done
> > > >>>>> on a specific device, so it requires a device ID.
> > > >>>>>
> > > >>>>> The other reason it needs to be a full library is that
> > > >>>>> it will start a workload on the GPU and get completion notification
> > > >>>>> so we can integrate the GPU workload in a packet processing pipeline.
> > > >>>>
> > > >>>> I might have confused you. My intention is not to make to fit under mempool API.
> > > >>>>
> > > >>>> I agree that we need a separate library for this. My objection is only
> > > >>>> to not call libgpudev and
> > > >>>> call it libgpu. And have APIs with rte_gpu_ instead of rte_gpu_dev as
> > > >>>> it not like existing "device libraries" in DPDK and
> > > >>>> it like other "libraries" in DPDK.
> > > >>>
> > > >>> I think we should define a queue of processing actions,
> > > >>> so it looks like other device libraries.
> > > >>> And anyway I think a library managing a device class,
> > > >>> and having some device drivers deserves the name of device library.
> > > >>>
> > > >>> I would like to read more opinions.
> > > >>
> > > >> Since the library is an unified interface to GPU device drivers
> > > >> I think it should be named as in the patch - gpudev.
> > > >>
> > > >> Mempool looks like an exception here - initially it was pure SW
> > > >> library, but not there are HW backends and corresponding device
> > > >> drivers.
> > > >>
> > > >> What I don't understand where is GPU specifics here?
> > > >
> > > > That's an interesting question.
> > > > Let's ask first what is a GPU for DPDK?
> > > > I think it is like a sub-CPU with high parallel execution capabilities,
> > > > and it is controlled by the CPU.
> > >
> > > I have no good ideas how to name it in accordance with
> > > above description to avoid "G" which for "Graphics" if
> > > understand correctly. However, may be it is not required.
> > > No strong opinion on the topic, but unbinding from
> > > "Graphics" would be nice.
> >
> > That's a question I ask myself for months now.
> > I am not able to find a better name,
> > and I start thinking that "GPU" is famous enough in high-load computing
> > to convey the idea of what we can expect.
> 
> 
> The closest I can think of is big-little architecture in ARM SoC.
> https://www.arm.com/why-arm/technologies/big-little
> 
> We do have similar architecture, Where the "coprocessor" is part of
> the main CPU.
> It is operations are:
> - Download firmware
> - Memory mapping for Main CPU memory by the co-processor
> - Enq/Deq Jobs from/to Main CPU/Coprocessor CPU.

Yes it looks like the exact same scope.
I like the word "co-processor" in this context.

> If your scope is something similar and No Graphics involved here then
> we can remove G.

Indeed no graphics in DPDK :)
By removing the G, you mean keeping only PU? like "pudev"?
We could also define the G as "General".

> Coincidentally, Yesterday, I had an interaction with Elena for the
> same for BaseBand related work in ORAN where
> GPU used as Baseband processing instead of Graphics.(So I can
> understand the big picture of this library)

Yes baseband processing is one possible usage of GPU with DPDK.
We could also imagine some security analysis, or any machine learning...

> I can think of "coprocessor-dev" as one of the name.

"coprocessor" looks too long as prefix of the functions.

> We do have similar machine learning co-processors(for compute)
> if we can keep a generic name and it is for the above functions we may
> use this subsystem as well in the future.

Yes that's the idea to share a common synchronization mechanism
with different HW.

That's cool to have such a big interest in the community for this patch.