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

[Jerin Jacob <jerinjacobk@gmail.com>]

On Fri, Jun 4, 2021 at 11:50 PM Wang, Haiyue <haiyue.wang@intel.com> wrote:
>
> > -----Original Message-----
> > From: dev <dev-bounces@dpdk.org> On Behalf Of Thomas Monjalon
> > Sent: Friday, June 4, 2021 23:51
> > To: Jerin Jacob <jerinjacobk@gmail.com>
> > Cc: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>; Andrew Rybchenko
> > <andrew.rybchenko@oktetlabs.ru>; Yigit, Ferruh <ferruh.yigit@intel.com>; dpdk-dev <dev@dpdk.org>;
> > Elena Agostini <eagostini@nvidia.com>; David Marchand <david.marchand@redhat.com>
> > Subject: Re: [dpdk-dev] [PATCH] gpudev: introduce memory API
> >
> > 04/06/2021 17:20, Jerin Jacob:
> > > 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.
> >
> > 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.

Yes. Libray name can be lengthy, but API prefix should be 3 letters
kind short form will be required.


> >
> > > 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.
> >
>
> Accelerator, 'acce_dev' ? ;-)

It may get confused with HW accelerators.


Some of the options I can think of. Sorting in my preference.

library name, API prefix
1) libhpc-dev, rte_hpc_ (hpc-> Heterogeneous processor compute)
2) libhc-dev, rte_hc_
(https://en.wikipedia.org/wiki/Heterogeneous_computing see: Example
hardware)
3) libpu-dev, rte_pu_ (pu -> processing unit)
4) libhp-dev, rte_hp_ (hp->heterogeneous processor)
5) libcoprocessor-dev, rte_cps_ ?
6) libcompute-dev, rte_cpt_ ?
7) libgpu-dev, rte_gpu_




>
> > 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.
> >
>