5. PVP reference benchmark setup using testpmd

This guide lists the steps required to setup a PVP benchmark using testpmd as a simple forwarder between NICs and Vhost interfaces. The goal of this setup is to have a reference PVP benchmark without using external vSwitches (OVS, VPP, ...) to make it easier to obtain reproducible results and to facilitate continuous integration testing.

The guide covers two ways of launching the VM, either by directly calling the QEMU command line, or by relying on libvirt. It has been tested with DPDK v16.11 using RHEL7 for both host and guest.

5.1. Setup overview

Fig. 5.16 PVP setup using 2 NICs

In this diagram, each red arrow represents one logical core. This use-case requires 6 dedicated logical cores. A forwarding configuration with a single NIC is also possible, requiring 3 logical cores.

5.2. Host setup

In this setup, we isolate 6 cores (from CPU2 to CPU7) on the same NUMA node. Two cores are assigned to the VM vCPUs running testpmd and four are assigned to testpmd on the host.

5.2.1. Host tuning

  1. On BIOS, disable turbo-boost and hyper-threads.

  2. Append these options to Kernel command line:

    intel_pstate=disable mce=ignore_ce default_hugepagesz=1G hugepagesz=1G hugepages=6 isolcpus=2-7 rcu_nocbs=2-7 nohz_full=2-7 iommu=pt intel_iommu=on
    
  3. Disable hyper-threads at runtime if necessary or if BIOS is not accessible:

    cat /sys/devices/system/cpu/cpu*[0-9]/topology/thread_siblings_list \
        | sort | uniq \
        | awk -F, '{system("echo 0 > /sys/devices/system/cpu/cpu"$2"/online")}'
    
  4. Disable NMIs:

    echo 0 > /proc/sys/kernel/nmi_watchdog
    
  5. Exclude isolated CPUs from the writeback cpumask:

    echo ffffff03 > /sys/bus/workqueue/devices/writeback/cpumask
    
  6. Isolate CPUs from IRQs:

    clear_mask=0xfc #Isolate CPU2 to CPU7 from IRQs
    for i in /proc/irq/*/smp_affinity
    do
      echo "obase=16;$(( 0x$(cat $i) & ~$clear_mask ))" | bc > $i
    done
    

5.2.2. Qemu build

Build Qemu:

git clone git://git.qemu.org/qemu.git
cd qemu
mkdir bin
cd bin
../configure --target-list=x86_64-softmmu
make

5.2.3. DPDK build

Build DPDK:

git clone git://dpdk.org/dpdk
cd dpdk
export RTE_SDK=$PWD
make install T=x86_64-native-linuxapp-gcc DESTDIR=install

5.2.4. Testpmd launch

  1. Assign NICs to DPDK:

    modprobe vfio-pci
    $RTE_SDK/install/sbin/dpdk-devbind -b vfio-pci 0000:11:00.0 0000:11:00.1
    

    Note

    The Sandy Bridge family seems to have some IOMMU limitations giving poor performance results. To achieve good performance on these machines consider using UIO instead.

  2. Launch the testpmd application:

    $RTE_SDK/install/bin/testpmd -l 0,2,3,4,5 --socket-mem=1024 -n 4 \
        --vdev 'net_vhost0,iface=/tmp/vhost-user1' \
        --vdev 'net_vhost1,iface=/tmp/vhost-user2' -- \
        --portmask=f --disable-hw-vlan -i --rxq=1 --txq=1 \
        --nb-cores=4 --forward-mode=io
    

    With this command, isolated CPUs 2 to 5 will be used as lcores for PMD threads.

  3. In testpmd interactive mode, set the portlist to obtain the correct port chaining:

    set portlist 0,2,1,3
    start
    

5.2.5. VM launch

The VM may be launched either by calling QEMU directly, or by using libvirt.

5.2.5.1. Qemu way

Launch QEMU with two Virtio-net devices paired to the vhost-user sockets created by testpmd. Below example uses default Virtio-net options, but options may be specified, for example to disable mergeable buffers or indirect descriptors.

<QEMU path>/bin/x86_64-softmmu/qemu-system-x86_64 \
    -enable-kvm -cpu host -m 3072 -smp 3 \
    -chardev socket,id=char0,path=/tmp/vhost-user1 \
    -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \
    -device virtio-net-pci,netdev=mynet1,mac=52:54:00:02:d9:01,addr=0x10 \
    -chardev socket,id=char1,path=/tmp/vhost-user2 \
    -netdev type=vhost-user,id=mynet2,chardev=char1,vhostforce \
    -device virtio-net-pci,netdev=mynet2,mac=52:54:00:02:d9:02,addr=0x11 \
    -object memory-backend-file,id=mem,size=3072M,mem-path=/dev/hugepages,share=on \
    -numa node,memdev=mem -mem-prealloc \
    -net user,hostfwd=tcp::1002$1-:22 -net nic \
    -qmp unix:/tmp/qmp.socket,server,nowait \
    -monitor stdio <vm_image>.qcow2

You can use this qmp-vcpu-pin script to pin vCPUs.

It can be used as follows, for example to pin 3 vCPUs to CPUs 1, 6 and 7, where isolated CPUs 6 and 7 will be used as lcores for Virtio PMDs:

export PYTHONPATH=$PYTHONPATH:<QEMU path>/scripts/qmp
./qmp-vcpu-pin -s /tmp/qmp.socket 1 6 7

5.2.5.2. Libvirt way

Some initial steps are required for libvirt to be able to connect to testpmd’s sockets.

First, SELinux policy needs to be set to permissive, since testpmd is generally run as root (note, as reboot is required):

cat /etc/selinux/config

# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing  - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled   - No SELinux policy is loaded.
SELINUX=permissive

# SELINUXTYPE= can take one of three two values:
#     targeted - Targeted processes are protected,
#     minimum  - Modification of targeted policy.
#                Only selected processes are protected.
#     mls      - Multi Level Security protection.
SELINUXTYPE=targeted

Also, Qemu needs to be run as root, which has to be specified in /etc/libvirt/qemu.conf:

user = "root"

Once the domain created, the following snippet is an extract of he most important information (hugepages, vCPU pinning, Virtio PCI devices):

<domain type='kvm'>
  <memory unit='KiB'>3145728</memory>
  <currentMemory unit='KiB'>3145728</currentMemory>
  <memoryBacking>
    <hugepages>
      <page size='1048576' unit='KiB' nodeset='0'/>
    </hugepages>
    <locked/>
  </memoryBacking>
  <vcpu placement='static'>3</vcpu>
  <cputune>
    <vcpupin vcpu='0' cpuset='1'/>
    <vcpupin vcpu='1' cpuset='6'/>
    <vcpupin vcpu='2' cpuset='7'/>
    <emulatorpin cpuset='0'/>
  </cputune>
  <numatune>
    <memory mode='strict' nodeset='0'/>
  </numatune>
  <os>
    <type arch='x86_64' machine='pc-i440fx-rhel7.0.0'>hvm</type>
    <boot dev='hd'/>
  </os>
  <cpu mode='host-passthrough'>
    <topology sockets='1' cores='3' threads='1'/>
    <numa>
      <cell id='0' cpus='0-2' memory='3145728' unit='KiB' memAccess='shared'/>
    </numa>
  </cpu>
  <devices>
    <interface type='vhostuser'>
      <mac address='56:48:4f:53:54:01'/>
      <source type='unix' path='/tmp/vhost-user1' mode='client'/>
      <model type='virtio'/>
      <driver name='vhost' rx_queue_size='256' />
      <address type='pci' domain='0x0000' bus='0x00' slot='0x10' function='0x0'/>
    </interface>
    <interface type='vhostuser'>
      <mac address='56:48:4f:53:54:02'/>
      <source type='unix' path='/tmp/vhost-user2' mode='client'/>
      <model type='virtio'/>
      <driver name='vhost' rx_queue_size='256' />
      <address type='pci' domain='0x0000' bus='0x00' slot='0x11' function='0x0'/>
    </interface>
  </devices>
</domain>

5.3. Guest setup

5.3.1. Guest tuning

  1. Append these options to the Kernel command line:

    default_hugepagesz=1G hugepagesz=1G hugepages=1 intel_iommu=on iommu=pt isolcpus=1,2 rcu_nocbs=1,2 nohz_full=1,2
    
  2. Disable NMIs:

    echo 0 > /proc/sys/kernel/nmi_watchdog
    
  3. Exclude isolated CPU1 and CPU2 from the writeback cpumask:

    echo 1 > /sys/bus/workqueue/devices/writeback/cpumask
    
  4. Isolate CPUs from IRQs:

    clear_mask=0x6 #Isolate CPU1 and CPU2 from IRQs
    for i in /proc/irq/*/smp_affinity
    do
      echo "obase=16;$(( 0x$(cat $i) & ~$clear_mask ))" | bc > $i
    done
    

5.3.2. DPDK build

Build DPDK:

git clone git://dpdk.org/dpdk
cd dpdk
export RTE_SDK=$PWD
make install T=x86_64-native-linuxapp-gcc DESTDIR=install

5.3.3. Testpmd launch

Probe vfio module without iommu:

modprobe -r vfio_iommu_type1
modprobe -r vfio
modprobe  vfio enable_unsafe_noiommu_mode=1
cat /sys/module/vfio/parameters/enable_unsafe_noiommu_mode
modprobe vfio-pci

Bind the virtio-net devices to DPDK:

$RTE_SDK/usertools/dpdk-devbind.py -b vfio-pci 0000:00:10.0 0000:00:11.0

Start testpmd:

$RTE_SDK/install/bin/testpmd -l 0,1,2 --socket-mem 1024 -n 4 \
    --proc-type auto --file-prefix pg -- \
    --portmask=3 --forward-mode=macswap --port-topology=chained \
    --disable-hw-vlan --disable-rss -i --rxq=1 --txq=1 \
    --rxd=256 --txd=256 --nb-cores=2 --auto-start

5.4. Results template

Below template should be used when sharing results:

Traffic Generator: <Test equipment (e.g. IXIA, Moongen, ...)>
Acceptable Loss: <n>%
Validation run time: <n>min
Host DPDK version/commit: <version, SHA-1>
Guest DPDK version/commit: <version, SHA-1>
Patches applied: <link to patchwork>
QEMU version/commit: <version>
Virtio features: <features (e.g. mrg_rxbuf='off', leave empty if default)>
CPU: <CPU model>, <CPU frequency>
NIC: <NIC model>
Result: <n> Mpps