251. Sample Application Tests: Multi-Process

251.1. Simple MP Application Test

251.1.1. Description

This test is a basic multi-process test which demonstrates the basics of sharing information between DPDK processes. The same application binary is run twice - once as a primary instance, and once as a secondary instance. Messages are sent from primary to secondary and vice versa, demonstrating the processes are sharing memory and can communicate using rte_ring structures.

251.1.2. Prerequisites

If using vfio the kernel must be >= 3.6+ and VT-d must be enabled in bios.When using vfio, use the following commands to load the vfio driver and bind it to the device under test:

modprobe vfio
modprobe vfio-pci
usertools/dpdk-devbind.py --bind=vfio-pci device_bus_id

Assuming that a DPDK build has been set up and the multi-process sample applications have been built.

251.1.3. Test Case: Basic operation

  1. To run the application, start one copy of the simple_mp binary in one terminal, passing at least two cores in the coremask, as follows:

    ./build/simple_mp -c 3 --proc-type=primary

    The process should start successfully and display a command prompt as follows:

    $ ./build/simple_mp -c 3 --proc-type=primary
    EAL: coremask set to 3
    EAL: Detected lcore 0 on socket 0
    EAL: Detected lcore 1 on socket 0
    EAL: Detected lcore 2 on socket 0
    EAL: Detected lcore 3 on socket 0
    EAL: Requesting 2 pages of size 1073741824
    EAL: Requesting 768 pages of size 2097152
    EAL: Ask a virtual area of 0x40000000 bytes
    EAL: Virtual area found at 0x7ff200000000 (size = 0x40000000)
    EAL: check igb_uio module
    EAL: check module finished
    EAL: Master core 0 is ready (tid=54e41820)
    EAL: Core 1 is ready (tid=53b32700)
    Starting core 1
    simple_mp >
  2. To run the secondary process to communicate with the primary process, again run the same binary setting at least two cores in the coremask.:

    ./build/simple_mp -c C --proc-type=secondary

    Once the process type is specified correctly, the process starts up, displaying largely similar status messages to the primary instance as it initializes. Once again, you will be presented with a command prompt.

  3. Once both processes are running, messages can be sent between them using the send command. At any stage, either process can be terminated using the quit command.

    Validate that this is working by sending a message between each process, both from primary to secondary and back again. This is shown below.

    Transcript from the primary - text entered by used shown in {}:

    EAL: Master core 10 is ready (tid=b5f89820)
    EAL: Core 11 is ready (tid=84ffe700)
    Starting core 11
    simple_mp > {send hello_secondary}
    simple_mp > core 11: Received 'hello_primary'
    simple_mp > {quit}

    Transcript from the secondary - text entered by the user is shown in {}:

    EAL: Master core 8 is ready (tid=864a3820)
    EAL: Core 9 is ready (tid=85995700)
    Starting core 9
    simple_mp > core 9: Received 'hello_secondary'
    simple_mp > {send hello_primary}
    simple_mp > {quit}

251.1.4. Test Case: Load test of Simple MP application

  1. Start up the sample application using the commands outlined in steps 1 & 2 above.
  2. To load test, send a large number of strings (>5000), from the primary instance to the secondary instance, and then from the secondary instance to the primary. [NOTE: A good source of strings to use is /usr/share/dict/words which contains >400000 ascii strings on Fedora 14]

251.1.5. Test Case: Test use of Auto for Application Startup

  1. Start the primary application as in Test 1, Step 1, except replace --proc-type=primary with --proc-type=auto
  2. Validate that the application prints the line: EAL: Auto-detected process type: PRIMARY on startup.
  3. Start the secondary application as in Test 1, Step 2, except replace --proc-type=secondary with --proc-type=auto.
  4. Validate that the application prints the line: EAL: Auto-detected process type: SECONDARY on startup.
  5. Verify that processes can communicate by sending strings, as in Test 1, Step 3.

251.1.6. Test Case: Test running multiple processes without “–proc-type” flag

  1. Start up the primary process as in Test 1, Step 1, except omit the --proc-type flag completely.

  2. Validate that process starts up as normal, and returns the simple_mp> prompt.

  3. Start up the secondary process as in Test 1, Step 2, except omit the --proc-type flag.

  4. Verify that the process fails to start and prints an error message as below:

    "PANIC in rte_eal_config_create():
    Cannot create lock on '/path/to/.rte_config'. Is another primary process running?"

251.2. Symmetric MP Application Test

251.2.1. Description

This test is a multi-process test which demonstrates how multiple processes can work together to perform packet I/O and packet processing in parallel, much as other example application work by using multiple threads. In this example, each process reads packets from all network ports being used - though from a different RX queue in each case. Those packets are then forwarded by each process which sends them out by writing them directly to a suitable TX queue.

251.2.2. Prerequisites

Assuming that an Intel� DPDK build has been set up and the multi-process sample applications have been built. It is also assumed that a traffic generator has been configured and plugged in to the NIC ports 0 and 1.

251.2.3. Test Methodology

As with the simple_mp example, the first instance of the symmetric_mp process must be run as the primary instance, though with a number of other application specific parameters also provided after the EAL arguments. These additional parameters are:

  • -p <portmask>, where portmask is a hexadecimal bitmask of what ports on the system are to be used. For example: -p 3 to use ports 0 and 1 only.
  • –num-procs <N>, where N is the total number of symmetric_mp instances that will be run side-by-side to perform packet processing. This parameter is used to configure the appropriate number of receive queues on each network port.
  • –proc-id <n>, where n is a numeric value in the range 0 <= n < N (number of processes, specified above). This identifies which symmetric_mp instance is being run, so that each process can read a unique receive queue on each network port.

The secondary symmetric_mp instances must also have these parameters specified, and the first two must be the same as those passed to the primary instance, or errors result.

For example, to run a set of four symmetric_mp instances, running on lcores 1-4, all performing level-2 forwarding of packets between ports 0 and 1, the following commands can be used (assuming run as root):

./build/symmetric_mp -c 2 --proc-type=auto -- -p 3 --num-procs=4 --proc-id=0
./build/symmetric_mp -c 4 --proc-type=auto -- -p 3 --num-procs=4 --proc-id=1
./build/symmetric_mp -c 8 --proc-type=auto -- -p 3 --num-procs=4 --proc-id=2
./build/symmetric_mp -c 10 --proc-type=auto -- -p 3 --num-procs=4 --proc-id=3

To run only 1 or 2 instances, the above parameters to the 1 or 2 instances being run should remain the same, except for the num-procs value, which should be adjusted appropriately.

251.2.4. Test Case: Performance Tests

Run the multiprocess application using standard IP traffic - varying source and destination address information to allow RSS to evenly distribute packets among RX queues. Record traffic throughput results as below.

Num-procs 1 2 2 4 4 8
Cores/Threads 1/1 1/2 2/1 2/2 4/1 4/2
Num Ports 2 2 2 2 2 2
Packet Size 64 64 64 64 64 64
%-age Line Rate X X X X X X
Packet Rate(mpps) X X X X X X

251.3. Client Server Multiprocess Tests

251.3.1. Description

The client-server sample application demonstrates the ability of Intel� DPDK to use multiple processes in which a server process performs packet I/O and one or multiple client processes perform packet processing. The server process controls load balancing on the traffic received from a number of input ports to a user-specified number of clients. The client processes forward the received traffic, outputting the packets directly by writing them to the TX rings of the outgoing ports.

251.3.2. Prerequisites

Assuming that an Intel� DPDK build has been set up and the multi-process sample application has been built. Also assuming a traffic generator is connected to the ports “0” and “1”.

It is important to run the server application before the client application, as the server application manages both the NIC ports with packet transmission and reception, as well as shared memory areas and client queues.

Run the Server Application:

  • Provide the core mask on which the server process is to run using -c, e.g. -c 3 (bitmask number).
  • Set the number of ports to be engaged using -p, e.g. -p 3 refers to ports 0 & 1.
  • Define the maximum number of clients using -n, e.g. -n 8.

The command line below is an example on how to start the server process on logical core 2 to handle a maximum of 8 client processes configured to run on socket 0 to handle traffic from NIC ports 0 and 1:

root@host:mp_server# ./build/mp_server -c 2 -- -p 3 -n 8

NOTE: If an additional second core is given in the coremask to the server process that second core will be used to print statistics. When benchmarking, only a single lcore is needed for the server process

Run the Client application:

  • In another terminal run the client application.
  • Give each client a distinct core mask with -c.
  • Give each client a unique client-id with -n.

An example commands to run 8 client processes is as follows:

root@host:mp_client# ./build/mp_client -c 40 --proc-type=secondary -- -n 0 &
root@host:mp_client# ./build/mp_client -c 100 --proc-type=secondary -- -n 1 &
root@host:mp_client# ./build/mp_client -c 400 --proc-type=secondary -- -n 2 &
root@host:mp_client# ./build/mp_client -c 1000 --proc-type=secondary -- -n 3 &
root@host:mp_client# ./build/mp_client -c 4000 --proc-type=secondary -- -n 4 &
root@host:mp_client# ./build/mp_client -c 10000 --proc-type=secondary -- -n 5 &
root@host:mp_client# ./build/mp_client -c 40000 --proc-type=secondary -- -n 6 &
root@host:mp_client# ./build/mp_client -c 100000 --proc-type=secondary -- -n 7 &

251.3.3. Test Case: Performance Measurement

  • On the traffic generator set up a traffic flow in both directions specifying IP traffic.
  • Run the server and client applications as above.
  • Start the traffic and record the throughput for transmitted and received packets.

An example set of results is shown below.

Server threads 1 1 1 1 1 1
Server Cores/Threads 1/1 1/1 1/1 1/1 1/1 1/1
Num-clients 1 2 2 4 4 8
Client Cores/Threads 1/1 1/2 2/1 2/2 4/1 4/2
Num Ports 2 2 2 2 2 2
Packet Size 64 64 64 64 64 64
%-age Line Rate X X X X X X
Packet Rate(mpps) X X X X X X