This document provides an overview and configuration instructions for DOCA GPUNetIO API.
Real-time GPU processing of network packets is a technique useful for application domains involving signal processing, network security, information gathering, input reconstruction, and more. These applications involve the CPU in the critical path (CPU-centric approach) to coordinate the network card (NIC) for receiving packets in the GPU memory (GPUDirect RDMA) and notifying a packet-processing CUDA kernel waiting on the GPU for a new set of packets. In lower-power platforms, the CPU can easily become the bottleneck, masking GPU value. The aim is to maximize the zero-packet-loss throughput at the the lowest latency possible.
A CPU-centric approach may not be scalable when increasing the number of clients connected to the application as the time between two receive operations on the same queue (client) would increase with the number of queues. The new DOCA GPUNetIO library allows developers to orchestrate these kinds of applications while optimizing performance, combining GPUDirect RDMA for data-path acceleration, GDRCopy library to give the CPU direct access to GPU memory, and GPUDirect Async kernel-initiated communications to allow a CUDA kernel to directly control the NIC.
CPU-centric approach:
GPU-centric approach:
DOCA GPUNetIO enables GPU-centric solutions that remove the CPU from the critical path by providing the following features:
GPUDirect Async Kernel-Initiated Network (GDAKIN) communications – a CUDA kernel can invoke GPUNetIO device functions to receive or send, directly interacting with the NIC
CPU intervention is not needed in the application critical path
GPUDirect RDMA – receive packets directly into a contiguous GPU memory area
Semaphores – provide a standardized I/O communication protocol between the receiving entity and the CUDA kernel real-time packet processing
Smart memory allocation – allocate aligned GPU memory buffers exposing them to direct CPU access
Combination of CUDA and DPDK gpudev library (which requires the GDRCopy library) already embedded in the DPDK released with DOCA
Ethernet protocol management on GPU
Morpheus and Aerial 5G SDK are examples of NVIDIA applications actively using DOCA GPUNetIO.
For a deep dive into the technology and motivations, please refer to the NVIDIA Blog post Inline GPU Packet Processing with NVIDIA DOCA GPUNetIO. A second NVIDIA blog post Realizing the Power of Real-Time Network Processing with NVIDIA DOCA GPUNetIO has been published to provide more example use-cases where DOCA GPUNetIO has been useful to improve the execution.
DOCA GPUNetIO requires a properly configured environment. The following subsections describe the required setup. DOCA GPUNetIO is available for all DOCA for host and BFB packages and it must be explicitly installed after the installation of the base DOCA packages.
Assuming the DOCA base package has been installed on the system, to install all DOCA GPUNetIO components, run:
apt install -y doca-gpu doca-gpu-dev
It is presumed that CUDA Toolkit and NVIDIA driver are installed on the system (host x86 or DPU Arm) where the DOCA GPUNetIO is built and executed.
Internal hardware topology of the system should be GPUDirect-RDMA-friendly to maximize the internal throughput between the GPU and the NIC.
As DOCA GPUNetIO is present in both DOCA for host and DOCA BFB (for DPU Arm), a GPUNetIO application can be executed either on the host CPU or on the Arm cores of the DPU. The following subsections provide a description of both scenarios.
DOCA GPUNetIO has been tested on bare-metal and in docker but never in a virtualized environment. Using KVM is discouraged for now.
Application on Host CPU
Assuming the DOCA GPUNetIO application is running on the host x86 CPU cores, it is highly recommended to have a dedicated PCIe connection between the GPU and the NIC. This topology can be realized in two ways:
Adding an additional PCIe switch to one of the PCIe root complex slots and attaching to this switch a GPU and a ConnectX adapter
Connecting an NVIDIA® Converged Accelerator DPU to the PCIe root complex and setting it to NIC mode (i.e., exposing the GPU and NIC devices to the host)
You may check the topology of your system using lspci -tvvv or nvidia-smi topo -m.
Option 1: ConnectX Adapter in Ethernet Mode
NVIDIA® ConnectX® firmware must be 22.36.1010 or later. It is highly recommended to only use NVIDIA adapter from ConnectX-6 Dx and later.
DOCA GPUNetIO allows a CUDA kernel to control the NIC when working with Ethernet protocol. For this reason, the ConnectX must be set to Ethernet mode.
To do that, follow these steps:
Start MST, check the status, and copy the MST device name:
# Start MSTmst start mst status -vMST modules: ------------ MST PCI module is not loaded MST PCI configuration module loaded PCI devices: ------------ DEVICE_TYPE MST PCI RDMA NET NUMA ConnectX6DX(rev:0) /dev/mst/mt4125_pciconf0.1 b5:00.1 mlx5_1 net-ens6f1 0 ConnectX6DX(rev:0) /dev/mst/mt4125_pciconf0 b5:00.0 mlx5_0 net-ens6f0 0Configure the NIC to Ethernet mode and enable Accurate Send Scheduling (if required on the send side):
NoteThe following example assumes that the adapter is dual-port. If single port, only P1 options apply.
mlxconfig -d /dev/mst/mt4125_pciconf0 s KEEP_ETH_LINK_UP_P1=1 KEEP_ETH_LINK_UP_P2=1 KEEP_IB_LINK_UP_P1=0 KEEP_IB_LINK_UP_P2=0 mlxconfig -d /dev/mst/mt4125_pciconf0 --
yessetACCURATE_TX_SCHEDULER=1 REAL_TIME_CLOCK_ENABLE=1Perform cold reboot to apply the configuration changes:
ipmitool power cycle
Option 2: DPU Converged Accelerator in NIC mode
DPU firmware must be 24.35.2000 or newer.
To expose and use the GPU and the NIC on the converged accelerator DPU to an application running on the Host x86, configure the DPU to operate in NIC mode.
To do that, follow these steps:
Valid for both BlueField-2 and BlueField-3 converged accelerator DPUs.
Start MST, check the status, and copy the MST device name:
# Enable MSTsudomst startsudomst status MST devices: ------------ /dev/mst/mt41686_pciconf0 - PCI configuration cycles access. domain:bus:dev.fn=0000:b8:00.0 addr.reg=88 data.reg=92 cr_bar.gw_offset=-1 Chip revision is: 01Expose the GPU on the converged accelerator DPU to the host.
For BlueField-2, the PCI_DOWNSTREAM_PORT_OWNER offset must be set to 4:
sudomlxconfig -d /dev/mst/mt41686_pciconf0 --yess PCI_DOWNSTREAM_PORT_OWNER[4]=0x0For BlueField-3, the PCI_DOWNSTREAM_PORT_OWNER offset must be set to 8:
sudomlxconfig -d <MST device> --yess PCI_DOWNSTREAM_PORT_OWNER[8]=0x0
Set the DPU to Ethernet mode, enable Accurate Send Scheduling (if required on the send side), and set it to NIC mode:
sudomlxconfig -d /dev/mst/mt41686_pciconf0 --yessetLINK_TYPE_P1=2 LINK_TYPE_P2=2sudomlxconfig -d /dev/mst/mt41686_pciconf0 --yessetINTERNAL_CPU_MODEL=1 INTERNAL_CPU_PAGE_SUPPLIER=1 INTERNAL_CPU_ESWITCH_MANAGER=1 INTERNAL_CPU_IB_VPORT0=1 INTERNAL_CPU_OFFLOAD_ENGINE=DISABLEDsudomlxconfig -d /dev/mst/mt41686_pciconf0 --yessetACCURATE_TX_SCHEDULER=1 REAL_TIME_CLOCK_ENABLE=1Perform cold reboot to apply the configuration changes:
ipmitool power cycle
Verify configuration:
sudomlxconfig -d /dev/mst/mt41686_pciconf0 q LINK_TYPE_P1 LINK_TYPE_P2 INTERNAL_CPU_MODEL INTERNAL_CPU_PAGE_SUPPLIER INTERNAL_CPU_ESWITCH_MANAGER INTERNAL_CPU_IB_VPORT0 INTERNAL_CPU_OFFLOAD_ENGINE ACCURATE_TX_SCHEDULER REAL_TIME_CLOCK_ENABLE LINK_TYPE_P1 ETH(2) LINK_TYPE_P2 ETH(2) INTERNAL_CPU_MODEL EMBEDDED_CPU(1) INTERNAL_CPU_PAGE_SUPPLIER EXT_HOST_PF(1) INTERNAL_CPU_ESWITCH_MANAGER EXT_HOST_PF(1) INTERNAL_CPU_IB_VPORT0 EXT_HOST_PF(1) INTERNAL_CPU_OFFLOAD_ENGINE DISABLED(1) ACCURATE_TX_SCHEDULER True(1) REAL_TIME_CLOCK_ENABLE True(1)
Application on DPU Converged Arm CPU
In this scenario, the DOCA GPUNetIO is running on the CPU Arm cores of the DPU using the GPU and NIC on the same DPU .
The converged accelerator DPU must be set to CPU mode after flashing the right BFB image (refer to NVIDIA DOCA Installation Guide for Linux for details). From the x86 host, configure the DPU as detailed in the following steps:
Valid for both BlueField-2 and BlueField-3 converged accelerator DPUs.
Start MST, check the status, and copy the MST device name:
# Enable MSTsudomst startsudomst status MST devices: ------------ /dev/mst/mt41686_pciconf0 - PCI configuration cycles access. domain:bus:dev.fn=0000:b8:00.0 addr.reg=88 data.reg=92 cr_bar.gw_offset=-1 Chip revision is: 01Set the DPU as the GPU owner.
For BlueField-2 the PCI_DOWNSTREAM_PORT_OWNER offset must be set to 4:
sudomlxconfig -d /dev/mst/mt41686_pciconf0 --yess PCI_DOWNSTREAM_PORT_OWNER[4]=0xFFor BlueField-3 the PCI_DOWNSTREAM_PORT_OWNER offset must be set to 8:
sudomlxconfig -d <MST device> --yess PCI_DOWNSTREAM_PORT_OWNER[8]=0xF
Set the DPU to Ethernet mode and enable Accurate Send Scheduling (if required on the send side):
sudomlxconfig -d /dev/mst/mt41686_pciconf0 --yessetLINK_TYPE_P1=2 LINK_TYPE_P2=2sudomlxconfig -d /dev/mst/mt41686_pciconf0 --yessetINTERNAL_CPU_MODEL=1 INTERNAL_CPU_PAGE_SUPPLIER=0 INTERNAL_CPU_ESWITCH_MANAGER=0 INTERNAL_CPU_IB_VPORT0=0 INTERNAL_CPU_OFFLOAD_ENGINE=ENABLEDsudomlxconfig -d /dev/mst/mt41686_pciconf0 --yessetACCURATE_TX_SCHEDULER=1 REAL_TIME_CLOCK_ENABLE=1Perform cold reboot to apply the configuration changes:
ipmitool power cycle
Verify configuration:
mlxconfig -d /dev/mst/mt41686_pciconf0 q LINK_TYPE_P1 LINK_TYPE_P2 INTERNAL_CPU_MODEL INTERNAL_CPU_PAGE_SUPPLIER INTERNAL_CPU_ESWITCH_MANAGER INTERNAL_CPU_IB_VPORT0 INTERNAL_CPU_OFFLOAD_ENGINE ACCURATE_TX_SCHEDULER REAL_TIME_CLOCK_ENABLE ... Configurations: Next Boot LINK_TYPE_P1 ETH(2) LINK_TYPE_P2 ETH(2) INTERNAL_CPU_MODEL EMBEDDED_CPU(1) INTERNAL_CPU_PAGE_SUPPLIER ECPF(0) INTERNAL_CPU_ESWITCH_MANAGER ECPF(0) INTERNAL_CPU_IB_VPORT0 ECPF(0) INTERNAL_CPU_OFFLOAD_ENGINE ENABLED(0) ACCURATE_TX_SCHEDULER True(1) REAL_TIME_CLOCK_ENABLE True(1)
At this point, it should be possible to SSH into the DPU to access the OS installed on it. Before installing DOCA GPUNetIO as previously described, CUDA Toolkit (and NVIDIA driver) must be installed.
PCIe Configuration
On some x86 systems, the Access Control Services (ACS) must be disabled to ensure direct communication between the NIC and GPU, whether they reside on the same converged accelerator DPU or on different PCIe slots in the system. The recommended solution is to disable ACS control via BIOS (e.g., Supermicro or HPE). Alternatively, it is also possible to disable it via command line, but it may not be as effective as the BIOS option. Assuming system topology Option 2, with a converged accelerator DPU as follows:
$ lspci -tvvv...+-[0000:b0]-+-00.0 Intel Corporation Device 09a2
| +-00.1 Intel Corporation Device 09a4
| +-00.2 Intel Corporation Device 09a3
| +-00.4 Intel Corporation Device 0998
| \-02.0-[b1-b6]----00.0-[b2-b6]--+-00.0-[b3]--+-00.0 Mellanox Technologies MT42822 BlueField-2 integrated ConnectX-6 Dx network controller
| | +-00.1 Mellanox Technologies MT42822 BlueField-2 integrated ConnectX-6 Dx network controller
| | \-00.2 Mellanox Technologies MT42822 BlueField-2 SoC Management Interface
| \-01.0-[b4-b6]----00.0-[b5-b6]----08.0-[b6]----00.0 NVIDIA Corporation Device 20b8
The PCIe switch address to consider is b2:00.0 (entry point of the DPU). ACSCtl must have all negative values:
PCIe set
setpci -s b2:00.0 ECAP_ACS+6.w=0:fc
To verify that the setting has been applied correctly:
PCIe check
$ sudo lspci -s b2:00.0 -vvvv | grep -i ACSCtl
ACSCtl: SrcValid- TransBlk- ReqRedir- CmpltRedir- UpstreamFwd- EgressCtrl- DirectTrans-
Please refer to this page and this page for more information.
If the application still does not report any received packets, try to disable IOMMU. On some systems, it can be done from the BIOS looking for the the VT-d or IOMMU from the NorthBridge configuration and change that setting to Disable and save it. The system may also require adding intel_iommu=off or amd_iommu=off to the kernel options. That can be done through the grub command line as follows:
IOMMU
$ sudo vim /etc/default/grub
# GRUB_CMDLINE_LINUX_DEFAULT="iommu=off intel_iommu=off <more options>"
$ sudo update-grub
$ sudo reboot
Hugepages
A DOCA GPUNetIO application over Ethernet uses typically DOCA Flow to set flow steering rules to the Ethernet receive queues. Flow-based programs require an allocation of huge pages and it can be done temporarily as explained in the DOCA Flow or permanently via grub command line:
IOMMU
$ sudo vim /etc/default/grub
# GRUB_CMDLINE_LINUX_DEFAULT="default_hugepagesz=1G hugepagesz=1G hugepages=4 <more options>"
$ sudo update-grub
$ sudo reboot
# After rebooting, check huge pages info
$ grep -i huge /proc/meminfo
AnonHugePages: 0 kB
ShmemHugePages: 0 kB
FileHugePages: 0 kB
HugePages_Total: 4
HugePages_Free: 4
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 1048576 kB
Hugetlb: 4194304 kB
GPU Configuration
CUDA Toolkit 12.1 or newer must be installed on the host. It is also recommended to enable persistence mode to decrease initial application latency nvidia-smi -pm 1.
To allow the CPU to access the GPU memory directly without the need for CUDA API, DPDK and DOCA require the GDRCopy kernel module to be installed on the system:
GPU Configuration
# Run nvidia-peermem kernel module
sudo modprobe nvidia-peermem
# Install GDRCopy
sudo apt install -y check kmod
git clone https://github.com/NVIDIA/gdrcopy.git /opt/mellanox/gdrcopy
cd /opt/mellanox/gdrcopy
make
# Run gdrdrv kernel module
./insmod.sh
# Double check nvidia-peermem and gdrdrv module are running
$ lsmod | egrep gdrdrv
gdrdrv 24576 0
nvidia 55726080 4 nvidia_uvm,nvidia_peermem,gdrdrv,nvidia_modeset
# Export library path
export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/opt/mellanox/gdrcopy/src
# Ensure CUDA library path is in the env var
export PATH="/usr/local/cuda/bin:${PATH}"
export LD_LIBRARY_PATH="/usr/local/cuda/lib:/usr/local/cuda/lib64:${LD_LIBRARY_PATH}"
export CPATH="$(echo /usr/local/cuda/targets/{x86_64,sbsa}-linux/include | sed 's/ /:/'):${CPATH}"
BlueField-3 Specific Configuration
To run a DOCA GPUNetIO application on the Arm DPU cores in a BlueField-3 converged card (section "Application on DPU Converged Arm CPU"), it is mandatory to set an NVIDIA driver option at the end of the driver configuration file:
Set NVIDIA driver option
cat <<EOF | sudo tee /etc/modprobe.d/nvidia.conf
options nvidia NVreg_RegistryDwords="RmDmaAdjustPeerMmioBF3=1;"
EOF
To make sure the option has been detected by the NVIDIA driver, run:
Check NVIDIA driver option
$ grep RegistryDwords /proc/driver/nvidia/params
RegistryDwords: "RmDmaAdjustPeerMmioBF3=1;"
RegistryDwordsPerDevice: ""
GPU Memory Mapping (nvidia-peermem vs. dmabuf)
To allow the NIC to send and receive packets using GPU memory, it is required to launch the NVIDIA kernel module nvidia-peermem (using modprobe nvidia-peermem). It is shipped by default with the CUDA Toolkit installation.
Mapping buffers through the nvidia-peermem module is the legacy mapping mode.
Alternatively, DOCA offers the ability to map GPU memory through the dmabuf providing a set high-level functions. Prerequisites are DOCA installed on a system with:
Linux Kernel ≥ 6.2
libibverbs ≥ 1.14.44
CUDA Toolkit installed with the -m=kernel-open flag (which implies the NVIDIA driver in Open Source mode)
Installing DOCA on kernel 6.2 to enable the dmabuf is experimental.
An example can be found in the DOCA GPU Packet Processing application:
GPU Configuration
/* Get from CUDA the dmabuf file-descriptor for the GPU memory buffer */
result = doca_gpu_dmabuf_fd(gpu_dev, gpu_buffer_addr, gpu_buffer_size, &(dmabuf_fd));
if (result != DOCA_SUCCESS) {
/* If it fails, create a DOCA mmap for the GPU memory buffer with the nvidia-peermem legacy method */
doca_mmap_set_memrange(gpu_buffer_mmap, gpu_buffer_addr, gpu_buffer_size);
} else {
/* If it succeeds, create a DOCA mmap for the GPU memory buffer using the dmabuf method */
doca_mmap_set_dmabuf_memrange(gpu_buffer_mmap, dmabuf_fd, gpu_buffer_addr, 0, gpu_buffer_size);
}
If the function doca_gpu_dmabuf_fd fails, it probably means the NVIDIA driver is not installed with the open-source mode.
Later, when calling the doca_mmap_start, the DOCA library tries to map the GPU memory buffer using the dmabuf file descriptor. If it fails (something incorrectly set on the Linux system), it fallbacks trying to map the GPU buffer with the legacy mode (nvidia-peermem ). If it fails, an informative error is returned.
GPU BAR1 Size
Every time a GPU buffer is mapped to the NIC (e.g., buffers associated with send or receive queues), a portion of the GPU BAR1 mapping space is used. Therefore, it is important to check that the BAR1 mapping is large enough to hold all the bytes the DOCA GPUNetIO application is trying to map. To verify the BAR1 mapping space of a GPU you can use nvidia-smi:
BAR1 mapping
$ nvidia-smi -q
==============NVSMI LOG==============
.....
Attached GPUs : 1
GPU 00000000:CA:00.0
Product Name : NVIDIA A100 80GB PCIe
Product Architecture : Ampere
Persistence Mode : Enabled
.....
BAR1 Memory Usage
Total : 131072 MiB
Used : 1 MiB
Free : 131071 MiB
By default, some GPUs (e.g. RTX models) may have a very small BAR1 size:
BAR1 mapping
$ nvidia-smi -q | grep -i bar -A 3
BAR1 Memory Usage
Total : 256 MiB
Used : 6 MiB
Free : 250 MiB
If the BAR1 size is not enough, DOCA GPUNetIO applications may exit with errors because DOCA mmap fails to map the GPU memory buffers to the NIC (e.g., Failed to start mmap DOCA Driver call failure). To overcome this issue, the GPU BAR1 must be increased from the BIOS. The system should have "Resizable BAR" option enabled. For further information, refer to this NVIDIA forum post.
A GPU packet processing network application can be split into two fundamental phases:
Setup on the CPU (devices configuration, memory allocation, launch of CUDA kernels, etc.)
Main data path where GPU and NIC interact to exercise their functions
DOCA GPUNetIO provides different building blocks, some of them in combination with the DOCA Ethernet library, to create a full pipeline running entirely on the GPU.
During the setup phase on the CPU, applications must:
Prepare all the objects on the CPU.
Export a GPU handler for them.
Launch a CUDA kernel passing the object's GPU handler to work with the object during the data path.
For this reason, DOCA GPUNetIO is composed of two libraries:
libdoca_gpunetio with functions invoked by CPU to prepare the GPU, allocate memory and objects
libdoca_gpunetio_device with functions invoked by GPU within CUDA kernels during the data path
The pkgconfig file for the DOCA GPUNetIO shared library is doca-gpu.pc. However, there is no pkgconfig file for the DOCA GPUNetIO CUDA device's static library /opt/mellanox/doca/lib/x86_64-linux-gnu/libdoca_gpunetio_device.a, so it must be explicitly linked to the CUDA application if DOCA GPUNetIO CUDA device functions are required.
The following diagram presents the typical flow:
Refer to the NVIDIA DOCA GPU Packet Processing Application Guide for an example of using DOCA GPUNetIO to send and receive Ethernet packets.
This section details the specific structures and operations related to the main DOCA GPUNetIO API on CPU and GPU. GPUNetIO headers are:
doca_gpunetio.h – CPU functions
doca_gpunetio_dev_buf.cuh – GPU functions to manage a DOCA buffer array
doca_gpunetio_dev_eth_rxq.cuh – GPU functions to manage a DOCA Ethernet receive queue
doca_gpunetio_dev_eth_txq.cuh – GPU functions to manage a DOCA Ethernet send queue
doca_gpunetio_dev_sem.cuh – GPU functions to manage a DOCA GPUNetIO semaphore
This section lists the main functions of DOCA GPUNetIO. To better understand their usage, refer to section "Building Blocks" which includes several code examples.
To better understand structures, objects, and functions related to Ethernet send and receive, please refer to the DOCA Ethernet.
To better understand DOCA core objects like doca_mmap or doca_buf_array, please refer to the DOCA Core.
All DOCA Core and Ethernet object used with GPUNetIO have a GPU export function to obtain a GPU handler for that object. The following are a few examples:
doca_buf_array is exported as doca_gpu_buf_arr :
DOCA buf array
structdoca_mmap *mmap;structdoca_buf_arr *buf_arr_cpu;structdoca_gpu_buf_arr *buf_arr_gpu; doca_mmap_create(&(mmap));/* Populate and start mmap */doca_buf_arr_create(mmap, &buf_arr_cpu);/* Populate and start buf arr attributes. Set datapath on GPU *//* Export the buf array CPU handler to a buf array GPU handler */doca_buf_arr_get_gpu_handle(buf_arr_cpu, &(buf_arr_gpu));/* To use the GPU handler, pass it as parameter of the CUDA kernel */cuda_kernel<<<...>>>(buf_arr_gpu, ...);doca_eth_rxq is exported as doca_gpu_eth_rxq :
DOCA buf array
structdoca_mmap *mmap;structdoca_eth_rxq *eth_rxq_cpu;structdoca_gpu_eth_rxq *eth_rxq_gpu;structdoca_dev *ddev;/* Create DOCA network device ddev *//* Create the DOCA Ethernet receive queue */doca_eth_rxq_create(ddev, MAX_NUM_PACKETS, MAX_PACKET_SIZE, ð_rxq_cpu,);/* Populate and start Ethernet receive queue attributes. Set datapath on GPU *//* Export the Ethernet receive queue CPU handler to a Ethernet receive queue GPU handler */doca_eth_rxq_get_gpu_handle(eth_rxq_cpu, &(eth_rxq_gpu));/* To use the GPU handler, pass it as parameter of the CUDA kernel */cuda_kernel<<<...>>>(eth_rxq_gpu, ...);
CPU functions
In this section there is the list of DOCA GPUNetIO functions that can be used on the CPU only.
doca_gpu_mem_type
This enum lists all the possible memory types that can be allocated with GPUNetIO.
enum doca_gpu_mem_type {
DOCA_GPU_MEM_TYPE_GPU = 0,
DOCA_GPU_MEM_TYPE_GPU_CPU = 1,
DOCA_GPU_MEM_TYPE_CPU_GPU = 2,
};
With regards to the syntax, the text string after the DOCA_GPU_MEM_TYPE_ prefix signifies <where-memory-resides>_<who-has-access>.
DOCA_GPU_MEM_TYPE_GPU – memory resides on the GPU and is accessible from the GPU only
DOCA_GPU_MEM_TYPE_GPU_CPU – memory resides on the GPU and is accessible also by the CPU
DOCA_GPU_MEM_TYPE_CPU_GPU – memory resides on the CPU and is accessible also by the GPU
Typical usage of the DOCA_GPU_MEM_TYPE_GPU_CPU memory type is to send a notification from the CPU to the GPU (e.g., a CUDA kernel periodically checking to see if the exit condition set by the CPU is met).
doca_gpu_create
This is the first function a GPUNetIO application must invoke to create an handler on a GPU device. The function initializes a pointer to a structure in memory with type struct doca_gpu *.
doca_error_t doca_gpu_create(const char *gpu_bus_id, struct doca_gpu **gpu_dev);
gpu_bus_id – <PCIe-bus>:<device>.<function> of the GPU device you want to use in your application
gpu_dev [out] – GPUNetIO handler to that GPU device
To get the PCIe address, users can use the commands lspci or nvidia-smi.
doca_gpu_mem_alloc
This CPU function allocates different flavors of memory.
doca_error_t doca_gpu_mem_alloc(struct doca_gpu *gpu_dev, size_t size, size_t alignment, enum doca_gpu_mem_type mtype, void **memptr_gpu, void **memptr_cpu)
gpu_dev – GPUNetIO device handler
size – Size, in bytes, of the memory area to allocate
alignment – Memory address alignment to use. If 0, default one will be used
mtype – Type of memory to allocate
memptr_gpu [out] – GPU pointer to use to modify that memory from the GPU if memory is allocated on or is visible by the GPU
memptr_cpu[out] – CPU pointer to use to modify that memory from the CPU if memory is allocated on or is visible by the CPU. Can be NULL if memory is GPU-only
Make sure to use the right pointer on the right device! I f an application tries to access the memory using the memptr_gpu address from the CPU, a segmentation fault will result.
doca_gpu_semaphore_create
Creates a new instance of a DOCA GPUNetIO semaphore. A semaphore is composed by a list of items each having, by default, a status flag, number of packets, and the index of a doca_gpu_buf in a doca_gpu_buf_arr.
For example, a GPUNetIO semaphore can be used in applications where a CUDA kernel is responsible for receiving packets in a doca_gpu_buf_arr array associated with an Ethernet receive queue object, doca_gpu_eth_rxq (see section "doca_gpu_dev_eth_rxq_receive_*"), and dispatching packet info to a second CUDA kernel which processes them.
Another way to use a GPUNetIO semaphore is to exchange data across different entities like two CUDA kernels or a CUDA kernel and a CPU thread. The reason for this scenario may be that the CUDA kernel needs to provide the outcome of the packet processing to the CPU which would in turn compile a statistics report. Therefore, it is possible to associate a custom application-defined structure to each item in the semaphore. This way, the semaphore can be used as a message passing object.
Both situations are illustrated in the "Receive and Process" section.
Entities communicating through a semaphore must adopt a poll/update mechanism according to the following logic:
Update:
Populate the next item of the semaphore (packets' info and/or custom application-defined info).
Set status flag to READY.
Poll:
Wait for the next item to have a status flag equal to READY.
Read and process info.
Set status flag to DONE.
doca_error_t doca_gpu_semaphore_create(struct doca_gpu *gpu_dev, struct doca_gpu_semaphore **semaphore)
gpu_dev – GPUNetIO handler
semaphore [out] – GPUNetIO semaphore handler associated to the GPU device
doca_gpu_semaphore_set_memory_type
This function defines the type of memory for the semaphore allocation.
doca_error_t doca_gpu_semaphore_set_memory_type(struct doca_gpu_semaphore *semaphore, enum doca_gpu_mem_type mtype)
semaphore – GPUNetIO semaphore handler
mtype – Type of memory to allocate the custom info structure
If the application must share packet info only across CUDA kernels, then DOCA_GPU_MEM_GPU is the suggested memory type.
If the application must share info from a CUDA kernel to a CPU (e.g., to report statistics or output of the pipeline computation), then DOCA_GPU_MEM_CPU_GPU is the suggested memory type
doca_gpu_semaphore_set_items_num
This function defines the number of items in a semaphore.
doca_error_t doca_gpu_semaphore_set_items_num(struct doca_gpu_semaphore *semaphore, uint32_t num_items)
semaphore – GPUNetIO semaphore handler
num_items – Number of items to allocate
doca_gpu_semaphore_set_custom_info
This function associates an application-specific structure to semaphore items as explained under "doca_gpu_semaphore_create".
doca_error_t doca_gpu_semaphore_set_custom_info(struct doca_gpu_semaphore *semaphore, uint32_t nbytes, enum doca_gpu_mem_type mtype)
semaphore – GPUNetIO semaphore handler
nbytes – Size of the custom info structure to associate
mtype – Type of memory to allocate the custom info structure
If the application must share packet info only across CUDA kernels, then DOCA_GPU_MEM_GPU is the suggested memory type
If the application must share info from a CUDA kernel to a CPU (e.g., to report statistics or output of the pipeline computation), then DOCA_GPU_MEM_CPU_GPU is the suggested memory type
doca_gpu_semaphore_get_status
From the CPU, query the status of a semaphore item. If the semaphore is allocated with DOCA_GPU_MEM_GPU, this function results in a segmentation fault.
doca_error_t doca_gpu_semaphore_get_status(struct doca_gpu_semaphore *semaphore_cpu, uint32_t idx, enum doca_gpu_semaphore_status *status)
semaphore_cpu – GPUNetIO semaphore CPU handler
idx – Semaphore item index
status [out] – Output semaphore status
doca_gpu_semaphore_get_custom_info_addr
From the CPU, retrieve the address of the custom info structure associated to a semaphore item. If the semaphore or the custom info is allocated with DOCA_GPU_MEM_GPU this function results in a segmentation fault.
doca_error_t doca_gpu_semaphore_get_custom_info_addr(struct doca_gpu_semaphore *semaphore_cpu, uint32_t idx, void **custom_info)
semaphore_cpu – GPUNetIO semaphore CPU handler
idx – Semaphore item index
custom_info [out] – Output semaphore custom info address
DOCA PE
A DOCA Ethernet Txq context, exported for GPUNetIO usage, can be tracked via DOCA PE on the CPU side to check if there are errors when sending packets or to retrieve notification info after sending a packet with any of the doca_gpu_dev_eth_txq_*_enqueue_* functions on the GPU. An example can be found in the DOCA GPU packet processing application with ICMP traffic.
GPU Functions
This section provides a list of DOCA GPUNetIO functions that can be used on the GPU only within a CUDA kernel.
doca_gpu_dev_eth_rxq_receive_*
To acquire packets in a CUDA kernel, DOCA GPUNetIO offers different flavors of the receive function for different scopes: per CUDA block, per CUDA warp, and per CUDA thread.
__device__ doca_error_t doca_gpu_dev_eth_rxq_receive_block(struct doca_gpu_eth_rxq *eth_rxq, uint32_t max_rx_pkts, uint64_t timeout_ns, uint32_t *num_rx_pkts, uint64_t *doca_gpu_buf_idx)
__device__ doca_error_t doca_gpu_dev_eth_rxq_receive_warp(struct doca_gpu_eth_rxq *eth_rxq, uint32_t max_rx_pkts, uint64_t timeout_ns, uint32_t *num_rx_pkts, uint64_t *doca_gpu_buf_idx)
__device__ doca_error_t doca_gpu_dev_eth_rxq_receive_thread(struct doca_gpu_eth_rxq *eth_rxq, uint32_t max_rx_pkts, uint64_t timeout_ns, uint32_t *num_rx_pkts, uint64_t *doca_gpu_buf_idx)
eth_rxq – Ethernet receive queue GPU handler
max_rx_pkts – Maximum number of packets allowed
timeout_ns – Nanoseconds to wait for packets before returning
num_rx_pkts [out] – Effective number of received packets. With CUDA block or warp scopes, this variable should be visible in memory by all the other threads (shared or global memory).
doca_gpu_buf_idx [out] – DOCA buffer index of the first packet received in this function. With CUDA block or warp scopes, this variable should be visible in memory by all the other threads (shared or global memory).
CUDA threads in the same scope (thread, warp, or block) must invoke the function on the same receive queue. The output parameters num_rx_pkts and doca_gpu_buf_idx must be visible by all threads in the scope (e.g., CUDA shared memory for warp and block).
Each packet received by this function goes to the doca_gpu_buf_arr internally created and associated with the Ethernet queues (see section "Building Blocks").
The function exits when timeout_ns is reached or when the maximum number of packets is received.
For CUDA block scope, the block invoking the receive function must have at least 32 CUDA threads (i.e., one warp).
The output parameters indicate how many packets have been actually received (num_rx_pkts) and the index of the first received packet in the doca_gpu_buf_arr internally associated with the Ethernet receive queue. Packets are stored consecutively in the doca_gpu_buf_arr so if the function returns num_rx_pkts=N and doca_gpu_buf_idx=X, this means that all the doca_gpu_buf in the doca_gpu_buf_arr within the range [X, .. ,X + (N-1)] have been filled with packets.
The DOCA buffer array is treated in a circular fashion so that once the last DOCA buffer is filled by a packet, the queue circles back to the first DOCA buffer. There is no need for the application to lock or free doca_gpu_buf_arr buffers.
It is the application's responsibility to consume packets before they are overwritten when circling back, properly dimensioning the DOCA buffer array size and scaling across multiple receive queues.
doca_gpu_send_flags
This enum lists all the possible flags for the txq functions. The usage of those flags makes sense if a DOCA PE has been attached to the DOCA Ethernet Txq context with GPU data path and a CPU thread, in a loop, keeps invoking doca_pe_progress.
If no DOCA PE has been attached to the DOCA Ethernet Txq context, it's mandatory to use the DOCA_GPU_SEND_FLAG_NONE flag.
enum doca_gpu_mem_type {
DOCA_GPU_SEND_FLAG_NONE = 0,
DOCA_GPU_SEND_FLAG_NOTIFY = 1 << 0,
};
Where:
DOCA_GPU_SEND_FLAG_NONE – default behaviour, send is executed and no notification info is returned. If an error occurs and event is generated. This error can be detected from the CPU side using DOCA PE.
DOCA_GPU_SEND_FLAG_NOTIFY – once the send (or wait) is executed, return a notification with packet info. This notification can be detected from the CPU side using DOCA PE.
doca_gpu_dev_eth_txq_send_*
To send packets from a CUDA kernel, DOCA GPUNetIO offers a strong and weak modes for enqueuing a packet in the Ethernet TXQ. For both modes, the scope is the single CUDA thread each populating and enqueuing a different doca_gpu_buf from a doca_gpu_buf_arr.
Strong Mode:
It is generally recommended to use strong mode as weak mode is more complex and is reserved for expert users.
__device__ doca_error_t doca_gpu_dev_eth_txq_send_enqueue_strong(struct doca_gpu_eth_txq *eth_txq, const struct doca_gpu_buf *buf_ptr, const uint32_t nbytes, const uint32_t flags_bitmask)
eth_txq – Ethernet send queue GPU handler
buf_ptr – DOCA buffer from a DOCA GPU buffer array to be sent
nbytes – Number of bytes to be sent in the packet
flags_bitmask – One of the flags in the doca_gpu_send_flags enum
Weak Mode:
In weak mode, the developer must specify a queue descriptor number for where to enqueue the packet ensuring that no descriptor in the queue is left empty wrapping at a 16-bit mask.
__device__ doca_error_t doca_gpu_dev_eth_txq_send_enqueue_weak(const struct doca_gpu_eth_txq *eth_txq, const struct doca_gpu_buf *buf_ptr, const uint32_t nbytes, const uint32_t ndescr, const uint32_t flags_bitmask)
eth_txq – Ethernet send queue GPU handler
buf_ptr – DOCA buffer from a DOCA GPU buffer array to be sent
nbytes – Number of bytes to be sent in the packet
ndescr – Position in the queue to place the packet. Range: 0-0xFFFF.
flags_bitmask – One of the flags in the doca_gpu_send_flags enum
doca_gpu_dev_eth_txq_wait_*
To enable Accurate Send Scheduling, the "wait on time" barrier (based on timestamp) must be set in the send queue before enqueuing more packets. Like doca_gpu_dev_eth_txq_send_*, doca_gpu_dev_eth_txq_wait_* also has a strong and weak mode.
Strong Mode:
It is generally recommended to use strong mode as weak mode is more complex and is reserved for expert users.
__device__ doca_error_t doca_gpu_dev_eth_txq_wait_time_enqueue_strong(struct doca_gpu_eth_txq *eth_txq, const uint64_t wait_on_time_value, const uint32_t flags_bitmask)
eth_txq – Ethernet send queue GPU handler
wait_on_time_value – Timestamp to specify when packets must be sent after this barrier
flags_bitmask – One of the flags in the doca_gpu_send_flags enum
Weak Mode:
In weak mode, the developer must specify a queue descriptor number for where to enqueue the packet ensuring that no descriptor in the queue is left empty wrapping at a 16-bit mask.
__device__ doca_error_t doca_gpu_dev_eth_txq_wait_time_enqueue_weak(struct doca_gpu_eth_txq *eth_txq, const uint64_t wait_on_time_value, const uint32_t ndescr, const uint32_t flags_bitmask)
eth_txq – Ethernet send queue GPU handler
wait_on_time_value – Timestamp to specify when packets must be sent after this barrier
ndescr – Position in the queue to place the packet. Value spans from 0 to 0xFFFF.
flags_bitmask – One of the flags in the doca_gpu_send_flags enum
Please refer to section "GPUNetIO Samples" to understand how to enable and use Accurate Send Scheduling.
doca_gpu_dev_eth_txq_commit_*
After enqueuing all the packets to be sent and time barriers, a commit function must be invoked on the txq queue. The right commit function must be used according to the type of enqueue mode (i.e., strong or weak) used in doca_gpu_dev_eth_txq_send_* and doca_gpu_dev_eth_txq_wait_*.
Strong Mode:
__device__ doca_error_t doca_gpu_dev_eth_txq_commit_strong(struct doca_gpu_eth_txq *eth_txq)
eth_txq – Ethernet send queue GPU handler
Weak Mode:
__device__ doca_error_t doca_gpu_dev_eth_txq_commit_weak(struct doca_gpu_eth_txq *eth_txq, const uint32_t descr_num)
eth_txq – Ethernet send queue GPU handler
descr_num – Number of queue items enqueued thus far
Only one CUDA thread in the scope (CUDA block or CUDA warp) can invoke this function on the send queue after several enqueue operations. Typical flow is as follows:
All threads in the scope enqueue packets in the send queue.
Synchronization point.
Only one thread in the scope performs the send queue commit.
doca_gpu_dev_eth_txq_push
After committing, the items in the send queue must be actually pushed to the network card.
__device__ doca_error_t doca_gpu_dev_eth_txq_push(struct doca_gpu_eth_txq *eth_txq)
eth_txq – Ethernet send queue GPU handler
Only one CUDA thread in the scope (CUDA block or CUDA warp) can invoke this function on the send queue after several enqueue or commit operations. Typical flow is as follows:
All threads in the scope enqueue packets in the send queue.
Synchronization point.
Only one thread in the scope does the send queue commit.
Only one thread in the scope does the send queue push.
Section "Produce and Send" provides an example where the scope is a block (e.g., each CUDA block operates on a different Ethernet send queue).
This sections explains general concepts behind the fundamental building blocks to use when creating a DOCA GPUNetIO application.
Initialize GPU and NIC
When DOCA GPUNetIO is used in combination with the NIC to send or receive Ethernet traffic, the following must be performed to properly set up the application and devices:
GPUNetIO setup
uint16_t dpdk_port_id;
struct doca_dev *ddev;
struct doca_gpu *gdev;
char *eal_param[3] = {"", "-a", "00:00.0"};
/* Initialize DPDK with empty device. DOCA device will hot-plug the network card later. */
rte_eal_init(3, eal_param);
/* Create DOCA device on a specific network card */
doca_dpdk_port_probe(&ddev);
get_dpdk_port_id_doca_dev(&ddev, &dpdk_port_id);
/* Create GPUNetIO handler on a specific GPU */
doca_gpu_create(gpu_pcie_address, &gdev);
The application would may have to enable different items depending on the task at hand.
Ethernet Receive Queue
If the DOCA application must receive Ethernet packets, receive queues must be created. The receive queue works in a circular way: At creation time, each receive queue is associated with a DOCA buffer array allocated on the GPU by the application. Each DOCA buffer of the buffer array has a maximum fixed size.
GPUNetIO receive
/* Start DPDK device */
rte_eth_dev_start(dpdk_port_id);
/* Initialise DOCA Flow */
struct doca_flow_port_cfg port_cfg;
port_cfg.port_id = port_id;
doca_flow_init(port_cfg);
doca_flow_port_start();
struct doca_dev *ddev;
struct doca_eth_rxq *eth_rxq_cpu;
struct doca_gpu_eth_rxq *eth_rxq_gpu;
struct doca_mmap *mmap;
void *gpu_buffer;
/* Create DOCA Ethernet receive queues */
doca_eth_rxq_create(ddev, MAX_PACKETS_NUM, MAX_PACKETS_SIZE, ð_rxq_cpu);
/* Set Ethernet receive queue properties */
/* ... */
/* Create DOCA mmap in GPU memory to be used for the DOCA buffer array associated to this Ethernet queue */
doca_mmap_create(&mmap);
/* Set DOCA mmap properties */
doca_gpu_mem_alloc(gdev, buffer_size, alignment, DOCA_GPU_MEM_GPU, (void **)&gpu_buffer, NULL);
doca_mmap_start(mmap);
doca_eth_rxq_set_pkt_buffer(eth_rxq_cpu, mmap, 0, buffer_size);
/* This DOCA Ethernet Rxq object will be managed by the GPU */
doca_ctx_set_datapath_on_gpu();
/* Start the Ethernet queue object */
/* Export GPU handle for the receive queue */
doca_eth_rxq_get_gpu_handle(eth_rxq_cpu, ð_rxq_gpu);
It is mandatory to associate DOCA Flow pipe(s) to the receive queues. Otherwise, the application cannot receive any packet.
Ethernet Send Queue
If the DOCA application must send Ethernet packets, send queues must be created in combination with doca_gpu_buf_arr to prepare and send packets from GPU memory.
GPUNetIO receive
struct doca_dev *ddev;
struct doca_eth_txq *eth_txq_cpu;
struct doca_gpu_eth_txq *eth_txq_gpu;
/* Create DOCA Ethernet send queues */
doca_eth_txq_create(ddev, QUEUE_DEPTH, ð_txq_cpu);
/* Set properties to send queues */
/* This DOCA Ethernet Rxq object will be managed by the GPU */
doca_ctx_set_datapath_on_gpu();
/* Start the Ethernet queue object */
/* Export GPU handle for the send queue */
doca_eth_txq_get_gpu_handle(eth_txq_cpu, ð_txq_gpu);
/* Create DOCA mmap to define memory layout and type for the DOCA buf array */
struct doca_mmap *mmap;
doca_mmap_create(&mmap);
/* Set DOCA mmap properties */
/* Create DOCA buf arr and export it to GPU */
struct doca_buf_arr *buf_arr;
struct doca_gpu_buf_arr *buf_arr_gpu;
doca_buf_arr_create(mmap, &buf_arr);
/* Set DOCA buf array properties */
...
/* Export GPU handle for the buf arr */
doca_buf_arr_get_gpu_handle(buf_arr, &buf_arr_gpu);
Semaphore
If the DOCA application must dispatch some packets' info across CUDA kernels or from the CUDA kernel and some CPU thread, a semaphore must be created.
A semaphore is a list of items, allocated either on the GPU or CPU (depending on the use case) visible by both the GPU and CPU. This object can be used to discipline communication across items in the GPU pipeline between CUDA kernels or a CUDA kernel and a CPU thread.
By default, each semaphore item can hold info about its status (FREE, READY, HOLD, DONE, ERROR), the number of received packets, and an index of a doca_gpu_buf in a doca_gpu_buf_arr.
If the semaphore must be used to exchange data with the CPU, a preferred memory layout would be DOCA_GPU_MEM_CPU_GPU. Whereas, if the semaphore is only needed across CUDA kernels, DOCA_GPU_MEM_GPU is the best memory layout to use.
As an optional feature, if the application must pass more application-specific info through the semaphore items, it is possible to attach a custom structure to each item of the semaphore.
Semaphore
#define SEMAPHORE_ITEMS 1024
/* Application defined custom structure to pass info through semaphore items */
struct custom_info {
int a;
uint64_t b;
};
/* Semaphore to share info from the GPU to the CPU */
struct doca_gpu_semaphore *sem_to_cpu;
struct doca_gpu_semaphore_gpu *sem_to_cpu_gpu;
doca_gpu_semaphore_create(gdev, &sem_to_cpu);
doca_gpu_semaphore_set_memory_type(sem_to_cpu, DOCA_GPU_MEM_CPU_GPU);
doca_gpu_semaphore_set_items_num(sem_to_cpu, SEMAPHORE_ITEMS);
/* This is optional */
doca_gpu_semaphore_set_custom_info(sem_to_cpu, sizeof(struct custom_info), DOCA_GPU_MEM_CPU_GPU);
doca_gpu_semaphore_start(sem_to_cpu);
doca_gpu_semaphore_get_gpu_handle(sem_to_cpu, &sem_to_cpu_gpu);
/* Semaphore to share info across GPU CUDA kernels with no CPU involvment */
struct doca_gpu_semaphore *sem_to_gpu;
struct doca_gpu_semaphore_gpu *sem_to_gpu_gpu;
doca_gpu_semaphore_create(gdev, &sem_to_gpu);
doca_gpu_semaphore_set_memory_type(sem_to_gpu, DOCA_GPU_MEM_GPU);
doca_gpu_semaphore_set_items_num(sem_to_gpu, SEMAPHORE_ITEMS);
/* This is optional */
doca_gpu_semaphore_set_custom_info(sem_to_gpu, sizeof(struct custom_info), DOCA_GPU_MEM_GPU);
doca_gpu_semaphore_start(sem_to_gpu);
doca_gpu_semaphore_get_gpu_handle(sem_to_gpu, &sem_to_gpu_gpu);
Data Path on GPU
At this point, the application has created and initialized all the objects required by the GPU to exercise the data path to send or receive packets with GPUNetIO. The following subsections provide examples for doing that.
Receive and Process
In this example, the application must receive packets from different queues with a receiver CUDA kernel and dispatch packet info to a second CUDA kernel responsible for packet processing.
The CPU launches the CUDA kernels and waits on the semaphore for output:
CPU code
#define CUDA_THREADS 512
#define CUDA_BLOCKS 1
int semaphore_index = 0;
enum doca_gpu_semaphore_status status;
struct custom_info *gpu_info;
/* On the CPU */
cuda_kernel_receive_dispatch<<<CUDA_THREADS, CUDA_BLOCKS, ..., stream_0>>>(eth_rxq_gpu, sem_to_gpu_gpu)
cuda_kernel_process<<<CUDA_THREADS, CUDA_BLOCKS, ..., stream_1>>>(eth_rxq_gpu, sem_to_cpu_gpu, sem_to_gpu_gpu)
while(/* condition */) {
doca_gpu_semaphore_get_status(sem_to_cpu, semaphore_index, &status);
if (status == DOCA_GPU_SEMAPHORE_STATUS_READY) {
doca_gpu_semaphore_get_custom_info_addr(sem_to_cpu, semaphore_index, (void **)&(gpu_info));
report_info(gpu_info);
doca_gpu_semaphore_set_status(sem_to_cpu, semaphore_index, DOCA_GPU_SEMAPHORE_STATUS_FREE);
semaphore_index = (semaphore_index+1) % SEMAPHORE_ITEMS;
}
}
On the GPU, the two CUDA kernels are running on different streams:
GPU code
cuda_kernel_receive_dispatch(eth_rxq_gpu, sem_to_gpu_gpu) {
__shared__ uint32_t rx_pkt_num;
__shared__ uint64_t rx_buf_idx;
int semaphore_index = 0;
while (/* exit condition */) {
doca_gpu_dev_eth_rxq_receive_block(eth_rxq_gpu, MAX_NUM_RECEIVE_PACKETS, TIMEOUT_RECEIVE_NS, &rx_pkt_num, &rx_buf_idx);
if (threadIdx.x == 0 && rx_pkt_num > 0) {
doca_gpu_dev_sem_set_packet_info(sem_to_gpu_gpu, semaphore_index, DOCA_GPU_SEMAPHORE_STATUS_READY, rx_pkt_num, rx_buf_idx);
semaphore_index = (semaphore_index+1) % SEMAPHORE_ITEMS;
}
}
}
cuda_kernel_process(eth_rxq_gpu, sem_to_cpu_gpu, sem_to_gpu_gpu) {
__shared__ uint32_t rx_pkt_num;
__shared__ uint64_t rx_buf_idx;
int semaphore_index = 0;
int thread_buf_idx = 0;
struct doca_gpu_buf *buf_ptr;
uintptr_t buf_addr;
struct custom_info *gpu_info;
while (/* exit condition */) {
if (threadIdx.x == 0) {
do {
result = doca_gpu_dev_sem_get_packet_info_status(sem_to_gpu_gpu, semaphore_index, DOCA_GPU_SEMAPHORE_STATUS_READY, &rx_pkt_num, &rx_buf_idx);
} while(result != DOCA_ERROR_NOT_FOUND /* && other exit condition */);
}
__syncthreads();
thread_buf_idx = threadIdx.x;
while (thread_buf_idx < rx_pkt_num) {
/* Get DOCA GPU buffer from the GPU buffer in the receive queue */
doca_gpu_dev_eth_rxq_get_buf(eth_rxq_gpu, rx_buf_idx + thread_buf_idx, &buf_ptr);
/* Get DOCA GPU buffer memory address */
doca_gpu_dev_buf_get_addr(buf_ptr, &buf_addr);
/*
* Atomic here is has the entire CUDA block accesses the same semaphore to CPU.
* Smarter implementation can be done at warp level, with multiple semaphores, etc.. to avoid this atomic
*/
int semaphore_index_tmp = atomicAdd_block(&semaphore_index, 1);
semaphore_index_tmp = semaphore_index_tmp % SEMAPHORE_ITEMS;
doca_gpu_dev_sem_get_custom_info_addr(sem_to_cpu_gpu, semaphore_index_tmp, (void **)&gpu_info);
populate_custom_info(buf_addr, gpu_info);
doca_gpu_dev_sem_set_status(sem_to_cpu_gpu, semaphore_index_tmp, DOCA_GPU_SEMAPHORE_STATUS_READY);
}
__syncthreads();
if (threadIdx.x == 0) {
doca_gpu_dev_sem_set_status(sem_to_gpu_gpu, semaphore_index, DOCA_GPU_SEMAPHORE_STATUS_READY);
}
}
}
This code can be represented with the following diagram when multiple queues and/or semaphores are used:
Please note that receiving and dispatching packets to another CUDA kernel is not required. A simpler scenario can have a single CUDA kernel receiving and processing packets:
The drawback of this approach is that the time between two receives depends on the time taken by the CUDA kernel to process received packets.
The type of pipeline that must be built heavily depends on the specific use case.
Produce and Send
In this example, the GPU produces some data, stores it into packets and then sends them over the network. The CPU launches the CUDA kernels and continues doing other work:
CPU code
#define CUDA_THREADS 512
#define CUDA_BLOCKS 1
int semaphore_index = 0;
enum doca_gpu_semaphore_status status;
struct custom_info *gpu_info;
/* On the CPU */
cuda_kernel_produce_send<<<CUDA_THREADS, CUDA_BLOCKS, ..., stream_0>>>(eth_txq_gpu, buf_arr_gpu)
/* do other stuff */
On the GPU, the CUDA kernel fills the packets with meaningful data and sends them. In the following example, the scope is CUDA block so each block uses a different DOCA Ethernet send queue:
GPU code
cuda_kernel_produce_send(eth_txq_gpu, buf_arr_gpu) {
uint64_t doca_gpu_buf_idx = threadIdx.x;
struct doca_gpu_buf *buf;
uintptr_t buf_addr;
uint32_t packet_len;
while (/* exit condition */) {
/* Each CUDA thread retrieves doca_gpu_buf from doca_gpu_buf_arr */
doca_gpu_dev_buf_get_buf(buf_arr_gpu, doca_gpu_buf_idx, &buf);
/* Get memory address of the packet in the doca_gpu_buf */
doca_gpu_dev_buf_get_addr(buf, &buf_addr);
/* Application produces data and crafts the packet in the doca_gpu_buf */
populate_packet(buf_addr, &packet_len);
/* Enqueue packet in the send queue */
doca_gpu_dev_eth_txq_send_enqueue_strong(eth_txq_gpu, buf, packet_len, );
/* Synchronization point */
__synchthreads();
/* Only one CUDA thread in the block must commit and push the send queue */
if (threadIdx.x == 0) {
doca_gpu_dev_eth_txq_commit_strong(eth_txq_gpu, DOCA_GPU_SEND_FLAG_NONE);
doca_gpu_dev_eth_txq_push(eth_txq_gpu);
}
/* Synchronization point */
__synchthreads();
/* Assume all threads in the block pushed a packet in the send queue */
doca_gpu_buf_idx += CUDA_THREADS;
}
}
This section contains two samples that show how to enable simple GPUNetIO features. Be sure to correctly set the following environment variables:
Build the sample
export PATH=${PATH}:/usr/local/cuda/bin
export CPATH="$(echo /usr/local/cuda/targets/{x86_64,sbsa}-linux/include | sed 's/ /:/'):${CPATH}"
export PKG_CONFIG_PATH=${PKG_CONFIG_PATH}:/usr/lib/pkgconfig:/opt/mellanox/grpc/lib/{x86_64,aarch64}-linux-gnu/pkgconfig:/opt/mellanox/dpdk/lib/{x86_64,aarch64}-linux-gnu/pkgconfig:/opt/mellanox/doca/lib/{x86_64,aarch64}-linux-gnu/pkgconfigexport LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/usr/local/cuda/lib64:/opt/mellanox/gdrcopy/src:/opt/mellanox/dpdk/lib/{x86_64,aarch64}-linux-gnu:/opt/mellanox/doca/lib/{x86_64,aarch64}-linux-gnu
Send Wait Time
The sample shows how to enable Accurate Send Scheduling (or wait-on-time) in the context of a GPUNetIO application. Accurate Send Scheduling is the ability of an NVIDIA NIC to send packets in the future according to application-provided timestamps.
This feature is supported on ConnectX-6 Dx and later .
This NVIDIA blog post offers an example for how this feature has been used in 5G networks.
This DOCA GPUNetIO sample provides a simple application to send packets with Accurate Send Scheduling from the GPU .
Synchronizing Clocks
Before starting the sample, it is important to properly synchronize the CPU clock with the NIC clock. This way, timestamps provided by the system clock are synchronized with the time in the NIC.
For this purpose, at least the phc2sys service must be used. To install it on an Ubuntu system:
phc2sys
sudo apt install linuxptp
To start the phc2sys service properly, a config file must be created in /lib/systemd/system/phc2sys.service:
phc2sys
[Unit]
Description=Synchronize system clock or PTP hardware clock (PHC)
Documentation=man:phc2sys
[Service]
Restart=always
RestartSec=5s
Type=simple
ExecStart=/bin/sh -c "taskset -c 15 /usr/sbin/phc2sys -s /dev/ptp$(ethtool -T ens6f0 | grep PTP | awk '{print $4}') -c CLOCK_REALTIME -n 24 -O 0 -R 256 -u 256"
[Install]
WantedBy=multi-user.target
Now phc2sys service can be started:
phc2sys
sudo systemctl stop systemd-timesyncd
sudo systemctl disable systemd-timesyncd
sudo systemctl daemon-reload
sudo systemctl start phc2sys.service
To check the status of phc2sys:
phc2sys
$ sudo systemctl status phc2sys.service
● phc2sys.service - Synchronize system clock or PTP hardware clock (PHC)
Loaded: loaded (/lib/systemd/system/phc2sys.service; disabled; vendor preset: enabled)
Active: active (running) since Mon 2023-04-03 10:59:13 UTC; 2 days ago
Docs: man:phc2sys
Main PID: 337824 (sh)
Tasks: 2 (limit: 303788)
Memory: 560.0K
CPU: 52min 8.199s
CGroup: /system.slice/phc2sys.service
├─337824 /bin/sh -c "taskset -c 15 /usr/sbin/phc2sys -s /dev/ptp\$(ethtool -T enp23s0f1np1 | grep PTP | awk '{print \$4}') -c CLOCK_REALTIME -n 24 -O 0 -R >
└─337829 /usr/sbin/phc2sys -s /dev/ptp3 -c CLOCK_REALTIME -n 24 -O 0 -R 256 -u 256
Apr 05 16:35:52 doca-vr-045 phc2sys[337829]: [457395.040] CLOCK_REALTIME rms 8 max 18 freq +110532 +/- 27 delay 770 +/- 3
Apr 05 16:35:53 doca-vr-045 phc2sys[337829]: [457396.071] CLOCK_REALTIME rms 8 max 20 freq +110513 +/- 30 delay 769 +/- 3
Apr 05 16:35:54 doca-vr-045 phc2sys[337829]: [457397.102] CLOCK_REALTIME rms 8 max 18 freq +110527 +/- 30 delay 769 +/- 3
Apr 05 16:35:55 doca-vr-045 phc2sys[337829]: [457398.130] CLOCK_REALTIME rms 8 max 18 freq +110517 +/- 31 delay 769 +/- 3
Apr 05 16:35:56 doca-vr-045 phc2sys[337829]: [457399.159] CLOCK_REALTIME rms 8 max 19 freq +110523 +/- 32 delay 770 +/- 3
Apr 05 16:35:57 doca-vr-045 phc2sys[337829]: [457400.191] CLOCK_REALTIME rms 8 max 20 freq +110528 +/- 33 delay 770 +/- 3
Apr 05 16:35:58 doca-vr-045 phc2sys[337829]: [457401.221] CLOCK_REALTIME rms 8 max 19 freq +110512 +/- 38 delay 770 +/- 3
Apr 05 16:35:59 doca-vr-045 phc2sys[337829]: [457402.253] CLOCK_REALTIME rms 9 max 20 freq +110538 +/- 47 delay 770 +/- 4
Apr 05 16:36:00 doca-vr-045 phc2sys[337829]: [457403.281] CLOCK_REALTIME rms 8 max 21 freq +110517 +/- 38 delay 769 +/- 3
Apr 05 16:36:01 doca-vr-045 phc2sys[337829]: [457404.311] CLOCK_REALTIME rms 8 max 17 freq +110526 +/- 26 delay 769 +/- 3
...
At this point, the system and NIC clocks are synchronized so timestamps provided by the CPU are correctly interpreted by the NIC.
The timestamps you get may not reflect the real time and day. To get that, you must properly set the ptp4l service with an external grand master on the system. Doing that is out of the scope of this sample.
Running the Sample
The sample is shipped with the source files that must be built:
phc2sys
# Ensure DOCA and DPDK are in the pkgconfig environment variable
cd /opt/mellanox/doca/samples/doca_gpunetio/gpunetio_send_wait_time
meson build
ninja -C build
The sample sends 8 bursts of 32 raw Ethernet packets or 1kB to a dummy Ethernet address, 10:11:12:13:14:15, in a timed way. Program the NIC to send every t nanoseconds (command line option -t).
The following example programs a system with GPU PCIe address ca:00.0 and NIC PCIe address 17:00.0 to send 32 packets every 5 milliseconds:
Run
# Ensure DOCA and DPDK are in the LD_LIBRARY_PATH environment variable
$ sudo ./build/doca_gpunetio_send_wait_time -n 17:00.0 -g ca:00.0 -t 5000000[09:22:54:165778][1316878][DOCA][INF][gpunetio_send_wait_time_main.c:195][main] Starting the sample
[09:22:54:438260][1316878][DOCA][INF][gpunetio_send_wait_time_main.c:224][main] Sample configuration:
GPU ca:00.0
NIC 17:00.0
Timeout 5000000ns
EAL: Detected CPU lcores: 128
...
EAL: Probe PCI driver: mlx5_pci (15b3:a2d6) device: 0000:17:00.0 (socket 0)
[09:22:54:819996][1316878][DOCA][INF][gpunetio_send_wait_time_sample.c:607][gpunetio_send_wait_time] Wait on time supported mode: DPDK
EAL: Probe PCI driver: gpu_cuda (10de:20b5) device: 0000:ca:00.0 (socket 1)
[09:22:54:830212][1316878][DOCA][INF][gpunetio_send_wait_time_sample.c:252][create_tx_buf] Mapping send queue buffer (0x0x7f48e32a0000 size 262144B) with legacy nvidia-peermem mode
[09:22:54:832462][1316878][DOCA][INF][gpunetio_send_wait_time_sample.c:657][gpunetio_send_wait_time] Launching CUDA kernel to send packets
[09:22:54:842945][1316878][DOCA][INF][gpunetio_send_wait_time_sample.c:664][gpunetio_send_wait_time] Waiting 10 sec for 256 packets to be sent
[09:23:04:883309][1316878][DOCA][INF][gpunetio_send_wait_time_sample.c:684][gpunetio_send_wait_time] Sample finished successfully
[09:23:04:883339][1316878][DOCA][INF][gpunetio_send_wait_time_main.c:239][main] Sample finished successfully
To verify that packets are actually sent at the right time, use a packet sniffer on the other side (e.g., tcpdump):
phc2sys
$ sudo tcpdump -i enp23s0f1np1 -A -s 64
17:12:23.480318 IP5 (invalid)
Sent from DOCA GPUNetIO...........................
....
17:12:23.480368 IP5 (invalid)
Sent from DOCA GPUNetIO...........................
# end of first burst of 32 packets, bump to +5ms
17:12:23.485321 IP5 (invalid)
Sent from DOCA GPUNetIO...........................
...
17:12:23.485369 IP5 (invalid)
Sent from DOCA GPUNetIO...........................
# end of second burst of 32 packets, bump to +5ms
17:12:23.490278 IP5 (invalid)
Sent from DOCA GPUNetIO...........................
...
The output should show a jump of approximately 5 milliseconds every 32 packets.
tcpdump may increase latency in sniffing packets and reporting the receive timestamp, so the difference between bursts of 32 packets reported may be less than expected, especially with small interval times like 500 microseconds (-t 500000).
Simple Receive
This simple application shows the fundamental steps to build a DOCA GPUNetIO receiver application with one queue for UDP packets and one CUDA kernel receiving those packets from the GPU, printing packet info to the console.
Invoking a printf from a CUDA kernel is not good practice for release software and should be used only to print debug information as it slows down the overall execution of the CUDA kernel.
To build and run the application:
Build the sample
# Ensure DOCA and DPDK are in the pkgconfig environment variable
cd /opt/mellanox/doca/samples/doca_gpunetio/gpunetio_simple_receive
meson build
ninja -C build
To test the application, this guide assumes the usual setup with two machines: one with the DOCA receiver application and the second one acting as packet generator. As UDP packet generator, this example considers the nping application that can be easily installed easily on any Linux machine.
The command to send 10 UDP packets via nping on the packet generator machine is:
nping generator
$ nping --udp -c 10 -p 2090 192.168.1.1 --data-length 1024 --delay 500ms
Starting Nping 0.7.80 ( https://nmap.org/nping ) at 2023-11-20 11:05 UTC
SENT (0.0018s) UDP packet with 1024 bytes to 192.168.1.1:2090
SENT (0.5018s) UDP packet with 1024 bytes to 192.168.1.1:2090
SENT (1.0025s) UDP packet with 1024 bytes to 192.168.1.1:2090
SENT (1.5025s) UDP packet with 1024 bytes to 192.168.1.1:2090
SENT (2.0032s) UDP packet with 1024 bytes to 192.168.1.1:2090
SENT (2.5033s) UDP packet with 1024 bytes to 192.168.1.1:2090
SENT (3.0040s) UDP packet with 1024 bytes to 192.168.1.1:2090
SENT (3.5040s) UDP packet with 1024 bytes to 192.168.1.1:2090
SENT (4.0047s) UDP packet with 1024 bytes to 192.168.1.1:2090
SENT (4.5048s) UDP packet with 1024 bytes to 192.168.1.1:2090
Max rtt: N/A | Min rtt: N/A | Avg rtt: N/A
UDP packets sent: 10 | Rcvd: 0 | Lost: 10 (100.00%)
Nping done: 1 IP address pinged in 5.50 seconds
Assuming the DOCA Simple Receive sample is waiting on the other machine at IP address 192.168.1.1.
The DOCA Simple Receive sample is launched on a system with NIC at 17:00.1 PCIe address and GPU at ca:00.0 PCIe address:
DOCA Simple Receive
# Ensure DOCA and DPDK are in the LD_LIBRARY_PATH environment variable
$ sudo ./build/doca_gpunetio_simple_receive -n 17:00.1 -g ca:00.0
[11:00:30:397080][2328673][DOCA][INF][gpunetio_simple_receive_main.c:159][main] Starting the sample
[11:00:30:652622][2328673][DOCA][INF][gpunetio_simple_receive_main.c:189][main] Sample configuration:
GPU ca:00.0
NIC 17:00.1
EAL: Detected CPU lcores: 128
EAL: Detected NUMA nodes: 2
EAL: Detected shared linkage of DPDK
EAL: Multi-process socket /var/run/dpdk/rte/mp_socket
EAL: Selected IOVA mode 'PA'
EAL: VFIO support initialized
TELEMETRY: No legacy callbacks, legacy socket not created
EAL: Probe PCI driver: mlx5_pci (15b3:a2d6) device: 0000:17:00.1 (socket 0)
[11:00:31:036760][2328673][DOCA][WRN][engine_model.c:72][adapt_queue_depth] adapting queue depth to 128.
[11:00:31:928926][2328673][DOCA][WRN][engine_port.c:321][port_driver_process_properties] detected representor used in VNF mode (driver port id 0)
EAL: Probe PCI driver: gpu_cuda (10de:20b5) device: 0000:ca:00.0 (socket 1)
[11:00:31:977261][2328673][DOCA][INF][gpunetio_simple_receive_sample.c:425][create_rxq] Creating Sample Eth Rxq
[11:00:31:977841][2328673][DOCA][INF][gpunetio_simple_receive_sample.c:466][create_rxq] Mapping receive queue buffer (0x0x7f86cc000000 size 33554432B) with nvidia-peermem mode
[11:00:32:043182][2328673][DOCA][INF][gpunetio_simple_receive_sample.c:610][gpunetio_simple_receive] Launching CUDA kernel to receive packets
[11:00:32:055193][2328673][DOCA][INF][gpunetio_simple_receive_sample.c:614][gpunetio_simple_receive] Waiting for termination
Thread 0 received UDP packet with Eth src 10:70:fd:fa:77:f5 - Eth dst 10:70:fd:fa:77:e9
Thread 0 received UDP packet with Eth src 10:70:fd:fa:77:f5 - Eth dst 10:70:fd:fa:77:e9
Thread 0 received UDP packet with Eth src 10:70:fd:fa:77:f5 - Eth dst 10:70:fd:fa:77:e9
Thread 0 received UDP packet with Eth src 10:70:fd:fa:77:f5 - Eth dst 10:70:fd:fa:77:e9
Thread 0 received UDP packet with Eth src 10:70:fd:fa:77:f5 - Eth dst 10:70:fd:fa:77:e9
Thread 0 received UDP packet with Eth src 10:70:fd:fa:77:f5 - Eth dst 10:70:fd:fa:77:e9
Thread 0 received UDP packet with Eth src 10:70:fd:fa:77:f5 - Eth dst 10:70:fd:fa:77:e9
Thread 0 received UDP packet with Eth src 10:70:fd:fa:77:f5 - Eth dst 10:70:fd:fa:77:e9
Thread 0 received UDP packet with Eth src 10:70:fd:fa:77:f5 - Eth dst 10:70:fd:fa:77:e9
Thread 0 received UDP packet with Eth src 10:70:fd:fa:77:f5 - Eth dst 10:70:fd:fa:77:e9
# Type Ctrl+C to kill the sample
[11:01:44:265141][2328673][DOCA][INF][gpunetio_simple_receive_sample.c:45][signal_handler] Signal 2 received, preparing to exit!
[11:01:44:265189][2328673][DOCA][INF][gpunetio_simple_receive_sample.c:620][gpunetio_simple_receive] Exiting from sample
[11:01:44:265533][2328673][DOCA][INF][gpunetio_simple_receive_sample.c:362][destroy_rxq] Destroying Rxq
[11:01:44:307829][2328673][DOCA][INF][gpunetio_simple_receive_sample.c:631][gpunetio_simple_receive] Sample finished successfully
[11:01:44:307861][2328673][DOCA][INF][gpunetio_simple_receive_main.c:204][main] Sample finished successfully