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

[Jerin Jacob <jerinjacobk@gmail.com>]

On Fri, Jun 4, 2021 at 7:39 PM Thomas Monjalon <thomas@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@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@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.

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

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)

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










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