Re: [dpdk-dev] [RFC PATCH v2 0/7] heterogeneous computing library

[Elena Agostini <eagostini@nvidia.com>]

> -----Original Message-----
> From: Wang, Haiyue <haiyue.wang@intel.com>
> Sent: Monday, September 6, 2021 7:15 PM
> To: Elena Agostini <eagostini@nvidia.com>; Jerin Jacob
> <jerinjacobk@gmail.com>
> Cc: NBU-Contact-Thomas Monjalon <thomas@monjalon.net>; Jerin Jacob
> <jerinj@marvell.com>; dpdk-dev <dev@dpdk.org>; Stephen Hemminger
> <stephen@networkplumber.org>; David Marchand
> <david.marchand@redhat.com>; Andrew Rybchenko
> <andrew.rybchenko@oktetlabs.ru>; Honnappa Nagarahalli
> <honnappa.nagarahalli@arm.com>; Yigit, Ferruh <ferruh.yigit@intel.com>;
> techboard@dpdk.org
> Subject: RE: [dpdk-dev] [RFC PATCH v2 0/7] heterogeneous computing
> library
> 
> 
> > -----Original Message-----
> > From: Elena Agostini <eagostini@nvidia.com>
> > Sent: Tuesday, September 7, 2021 00:11
> > To: Jerin Jacob <jerinjacobk@gmail.com>
> > Cc: Wang, Haiyue <haiyue.wang@intel.com>; NBU-Contact-Thomas
> Monjalon
> > <thomas@monjalon.net>; Jerin Jacob <jerinj@marvell.com>; dpdk-dev
> > <dev@dpdk.org>; Stephen Hemminger <stephen@networkplumber.org>;
> David
> > Marchand <david.marchand@redhat.com>; Andrew Rybchenko
> > <andrew.rybchenko@oktetlabs.ru>; Honnappa Nagarahalli
> > <honnappa.nagarahalli@arm.com>; Yigit, Ferruh
> > <ferruh.yigit@intel.com>; techboard@dpdk.org
> > Subject: RE: [dpdk-dev] [RFC PATCH v2 0/7] heterogeneous computing
> > library
> >
> >
> >
> 
> 
> > > >
> > > > I'd like to introduce (with a dedicated option) the memory API in
> > > > testpmd to provide an example of how to TX/RX packets using device
> > > memory.
> > >
> > > Not sure without embedding sideband communication mechanism how
> it
> > > can notify to GPU and back to CPU. If you could share the example
> > > API sequence that helps to us understand the level of coupling with
> testpmd.
> > >
> >
> > There is no need of communication mechanism here.
> > Assuming there is not workload to process network packets (to not
> > complicate things), the steps are:
> > 1) Create a DPDK mempool with device external memory using the hcdev
> > (or gpudev) library
> > 2) Use that mempool to tx/rx/fwd packets
> >
> > As an example, you look at my l2fwd-nv application here:
> > https://github.com/NVIDIA/l2fwd-nv
> >
> 
> To enhance the 'rte_extmem_register' / 'rte_pktmbuf_pool_create_extbuf'
> ?
> 

The purpose of these two functions is different.
Here DPDK allows the user to use any kind of memory to rx/tx packets.
It's not about allocating memory.

Maybe I'm missing the point here: what's the main objection in having a GPU library?

>         if (l2fwd_mem_type == MEM_HOST_PINNED) {
>                 ext_mem.buf_ptr = rte_malloc("extmem", ext_mem.buf_len, 0);
>                 CUDA_CHECK(cudaHostRegister(ext_mem.buf_ptr,
> ext_mem.buf_len, cudaHostRegisterMapped));
>                 void *pDevice;
>                 CUDA_CHECK(cudaHostGetDevicePointer(&pDevice,
> ext_mem.buf_ptr, 0));
>                 if (pDevice != ext_mem.buf_ptr)
>                         rte_exit(EXIT_FAILURE, "GPU pointer does not match CPU
> pointer\n");
>         } else {
>                 ext_mem.buf_iova = RTE_BAD_IOVA;
>                 CUDA_CHECK(cudaMalloc(&ext_mem.buf_ptr,
> ext_mem.buf_len));
>                 if (ext_mem.buf_ptr == NULL)
>                         rte_exit(EXIT_FAILURE, "Could not allocate GPU memory\n");
> 
>                 unsigned int flag = 1;
>                 CUresult status = cuPointerSetAttribute(&flag,
> CU_POINTER_ATTRIBUTE_SYNC_MEMOPS, (CUdeviceptr)ext_mem.buf_ptr);
>                 if (CUDA_SUCCESS != status) {
>                         rte_exit(EXIT_FAILURE, "Could not set SYNC MEMOP attribute
> for GPU memory at %llx\n", (CUdeviceptr)ext_mem.buf_ptr);
>                 }
>                 ret = rte_extmem_register(ext_mem.buf_ptr, ext_mem.buf_len,
> NULL, ext_mem.buf_iova, GPU_PAGE_SIZE);
>                 if (ret)
>                         rte_exit(EXIT_FAILURE, "Could not register GPU memory\n");
>         }
>         ret = rte_dev_dma_map(rte_eth_devices[l2fwd_port_id].device,
> ext_mem.buf_ptr, ext_mem.buf_iova, ext_mem.buf_len);
>         if (ret)
>                 rte_exit(EXIT_FAILURE, "Could not DMA map EXT memory\n");
>         mpool_payload = rte_pktmbuf_pool_create_extbuf("payload_mpool",
> l2fwd_nb_mbufs,
>                                                                                         0, 0, ext_mem.elt_size,
>                                                                                         rte_socket_id(),
> &ext_mem, 1);
>         if (mpool_payload == NULL)
>                 rte_exit(EXIT_FAILURE, "Could not create EXT memory
> mempool\n");
> 
>