[ovs-dev] [PATCH 2/2] doc: Refactor DPDK install guide, add ADVANCED doc
Thomas F Herbert
thomasfherbert at gmail.com
Thu May 12 17:55:50 UTC 2016
On 5/9/16 2:32 AM, Bhanuprakash Bodireddy wrote:
> Add INSTALL.DPDK-ADVANCED document that is forked off from original
> INSTALL.DPDK guide. This document is targeted at users looking for
> optimum performance on OVS using dpdk datapath.
Thanks for this effort.
>
> Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy at intel.com>
> ---
> INSTALL.DPDK-ADVANCED.md | 809 +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 809 insertions(+)
> create mode 100644 INSTALL.DPDK-ADVANCED.md
>
> diff --git a/INSTALL.DPDK-ADVANCED.md b/INSTALL.DPDK-ADVANCED.md
> new file mode 100644
> index 0000000..dd09d36
> --- /dev/null
> +++ b/INSTALL.DPDK-ADVANCED.md
> @@ -0,0 +1,809 @@
> +OVS DPDK ADVANCED INSTALL GUIDE
> +=================================
> +
> +## Contents
> +
> +1. [Overview](#overview)
> +2. [Building Shared Library](#build)
> +3. [System configuration](#sysconf)
> +4. [Performance Tuning](#perftune)
> +5. [OVS Testcases](#ovstc)
> +6. [Vhost Walkthrough](#vhost)
> +7. [QOS](#qos)
> +8. [Static Code Analysis](#staticanalyzer)
> +9. [Vsperf](#vsperf)
> +
> +## <a name="overview"></a> 1. Overview
> +
> +The Advanced Install Guide explains how to improve OVS performance using
> +DPDK datapath. This guide also provides information on tuning, system configuration,
> +troubleshooting, static code analysis and testcases.
> +
> +## <a name="build"></a> 2. Building Shared Library
> +
> +DPDK can be built as static or shared library and shall be linked by applications
> +using DPDK datapath. The section lists steps to build shared library and dynamically
> +link DPDK against OVS.
> +
> +Note: Minor performance loss is seen with OVS when using shared DPDK library as
> +compared to static library.
> +
> +Check section 2.2, 2.3 of INSTALL.DPDK on download instructions
> +for DPDK and OVS.
> +
> + * Configure the DPDK library
> +
> + Set `CONFIG_RTE_BUILD_SHARED_LIB=y` in `config/common_base`
> + to generate shared DPDK library
> +
> +
> + * Build and install DPDK
> +
> + For Default install (without IVSHMEM), set `export DPDK_TARGET=x86_64-native-linuxapp-gcc`
> + For IVSHMEM case, set `export DPDK_TARGET=x86_64-ivshmem-linuxapp-gcc`
> +
> + ```
> + export DPDK_DIR=/usr/src/dpdk-16.04
> + export DPDK_BUILD=$DPDK_DIR/$DPDK_TARGET
> + make install T=$DPDK_TARGET DESTDIR=install
> + ```
> +
> + * Build, Install and Setup OVS.
> +
> + Export the DPDK shared library location and setup OVS as listed in
> + section 3.3 of INSTALL.DPDK.
> +
> + `export LD_LIBRARY_PATH=$DPDK_DIR/x86_64-native-linuxapp-gcc/lib`
> +
> +## <a name="sysconf"></a> 3. System Configuration
> +
> +To achieve optimal OVS performance, the system can be configured and that includes
> +BIOS tweaks, Grub cmdline additions, better understanding of NUMA nodes and
> +apt selection of PCIe slots for NIC placement.
> +
> +### 3.1 Recommended BIOS settings
> +
> + ```
> + | Settings | values | comments
> + |---------------------------|-----------|-----------
> + | C3 power state | Disabled | -
> + | C6 power state | Disabled | -
> + | MLC Streamer | Enabled | -
> + | MLC Spacial prefetcher | Enabled | -
> + | DCU Data prefetcher | Enabled | -
> + | DCA | Enabled | -
> + | CPU power and performance | Performance -
> + | Memory RAS and perf | | -
> + config-> NUMA optimized | Enabled | -
> + ```
> +
> +### 3.2 PCIe Slot Selection
> +
> +The fastpath performance also depends on factors like the NIC placement,
> +Channel speeds between PCIe slot and CPU, proximity of PCIe slot to the CPU
> +cores running DPDK application. Listed below are the steps to identify
> +right PCIe slot.
> +
> +- Retrieve host details using cmd `dmidecode -t baseboard | grep "Product Name"`
> +- Download the technical specification for Product listed eg: S2600WT2.
> +- Check the Product Architecture Overview on the Riser slot placement,
> + CPU sharing info and also PCIe channel speeds.
> +
> + example: On S2600WT, CPU1 and CPU2 share Riser Slot 1 with Channel speed between
> + CPU1 and Riser Slot1 at 32GB/s, CPU2 and Riser Slot1 at 16GB/s. Running DPDK app
> + on CPU1 cores and NIC inserted in to Riser card Slots will optimize OVS performance
> + in this case.
> +
> +- Check the Riser Card #1 - Root Port mapping information, on the available slots
> + and individual bus speeds. In S2600WT slot 1, slot 2 has high bus speeds and are
> + potential slots for NIC placement.
> +
> +### 3.3 Setup Hugepages
Advanced Hugepage setup.
> +
Basic huge page setup for 2MB huge pages is covered in INSTALL.DPDK.md.
This section
> + 1. Allocate Huge pages
> +
> + For persistent allocation of huge pages, add the following options to the kernel bootline
> + - 2MB huge pages:
> +
> + Add `hugepages=N`
> +
> + - 1G huge pages:
> +
> + Add `default_hugepagesz=1GB hugepagesz=1G hugepages=N`
> +
> + For platforms supporting multiple huge page sizes, Add options
> +
> + `default_hugepagesz=<size> hugepagesz=<size> hugepages=N`
> + where 'N' = Number of huge pages requested, 'size' = huge page size,
> + optional suffix [kKmMgG]
> +
> + For run-time allocation of huge pages
> +
> + - 2MB huge pages:
> +
> + `echo N > /proc/sys/vm/nr_hugepages`
> +
> + - 1G huge pages:
> +
> + `echo N > /sys/devices/system/node/nodeX/hugepages/hugepages-1048576kB/nr_hugepages`
> + where 'N' = Number of huge pages requested, 'X' = NUMA Node
> +
> + Note: For run-time allocation of 1G huge pages, Contiguous Memory Allocator(CONFIG_CMA)
> + has to be supported by kernel, check with your Linux distro.
> +
> + 2. Mount huge pages
> + - 2MB huge pages:
> +
> + `mount -t hugetlbfs none /dev/hugepages`
> +
> + - 1G huge pages:
> +
> + `mount -t hugetlbfs -o pagesize=1G none /dev/hugepages`
> +
> +### 3.4 Enable Hyperthreading
> +
> + Requires BIOS changes
> +
> + With HT/SMT enabled, A Physical core appears as two logical cores.
> + SMT can be utilized to spawn worker threads on logical cores of the same
> + physical core there by saving additional cores.
> +
> + With DPDK, When pinning pmd threads to logical cores, care must be taken
> + to set the correct bits in the pmd-cpu-mask to ensure that the pmd threads are
> + pinned to SMT siblings.
> +
> + Example System configuration:
> + Dual socket Machine, 2x 10 core processors, HT enabled, 40 logical cores
> +
> + To use two logical cores which share the same physical core for pmd threads,
> + the following command can be used to identify a pair of logical cores.
> +
> + `cat /sys/devices/system/cpu/cpuN/topology/thread_siblings_list`, where N is the
> + logical core number.
> +
> + In this example, it would show that cores 1 and 21 share the same physical core.
> + The pmd-cpu-mask to enable two pmd threads running on these two logical cores
> + (one physical core) is.
> +
> + `ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=100002`
> +
> +### 3.5 Isolate cores
> +
> + 'isolcpus' option can be used to isolate cores from the linux scheduler.
> + The isolated cores can then be used to dedicatedly run HPC applications/threads.
> + This helps in better application performance due to zero context switching and
> + minimal cache thrashing. To run platform logic on core 0 and isolate cores
> + between 1 and 19 from scheduler, Add `isolcpus=1-19` to GRUB cmdline.
> +
> + Note: It has been verified that core isolation has minimal advantage due to
> + mature Linux scheduler in some circumstances.
> +
> +### 3.6 NUMA/Cluster on Die
> +
> + Ideally inter NUMA datapaths should be avoided where possible as packets
> + will go across QPI and there may be a slight performance penalty when
> + compared with intra NUMA datapaths. On Intel Xeon Processor E5 v3,
> + Cluster On Die is introduced on models that have 10 cores or more.
> + This makes it possible to logically split a socket into two NUMA regions
> + and again it is preferred where possible to keep critical datapaths
> + within the one cluster.
> +
> + It is good practice to ensure that threads that are in the datapath are
> + pinned to cores in the same NUMA area. e.g. pmd threads and QEMU vCPUs
> + responsible for forwarding.
> +
> +### 3.7 Compiler Optimizations
> +
> + The default compiler optimization level is '-O2'. Changing this to
> + more aggressive compiler optimizations such as '-O3' or
> + '-Ofast -march=native' with gcc(verified on 5.3.1) can produce performance
> + gains though not siginificant. '-march=native' will produce optimized code
> + on local machine and should be used when SW compilation is done on Testbed.
> +
> +## <a name="perftune"></a> 4. Performance Tuning
> +
> +### 4.1 Affinity
> +
> +For superior performance, DPDK pmd threads and Qemu vCPU threads
> +needs to be affinitized accordingly.
> +
> + * PMD thread Affinity
> +
> + A poll mode driver (pmd) thread handles the I/O of all DPDK
> + interfaces assigned to it. A pmd thread shall poll the ports
> + for incoming packets, switch the packets and send to tx port.
> + pmd thread is CPU bound, and needs to be affinitized to isolated
> + cores for optimum performance.
> +
> + By setting a bit in the mask, a pmd thread is created and pinned
> + to the corresponding CPU core. e.g. to run a pmd thread on core 2
> +
> + `ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=4`
> +
> + Note: pmd thread on a NUMA node is only created if there is
> + at least one DPDK interface from that NUMA node added to OVS.
> +
> + * Qemu vCPU thread Affinity
> +
> + A VM performing simple packet forwarding or running complex packet
> + pipelines has to ensure that the vCPU threads performing the work has
> + as much CPU occupancy as possible.
> +
> + Example: On a multicore VM, multiple QEMU vCPU threads shall be spawned.
> + when the DPDK 'testpmd' application that does packet forwarding
> + is invoked, 'taskset' cmd should be used to affinitize the vCPU threads
> + to the dedicated isolated cores on the host system.
> +
> +### 4.2 Multiple poll mode driver threads
> +
> + With pmd multi-threading support, OVS creates one pmd thread
> + for each NUMA node by default. However, it can be seen that in cases
> + where there are multiple ports/rxq's producing traffic, performance
> + can be improved by creating multiple pmd threads running on separate
> + cores. These pmd threads can then share the workload by each being
> + responsible for different ports/rxq's. Assignment of ports/rxq's to
> + pmd threads is done automatically.
> +
> + A set bit in the mask means a pmd thread is created and pinned
> + to the corresponding CPU core. e.g. to run pmd threads on core 1 and 2
> +
> + `ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=6`
> +
> + For example, when using dpdk and dpdkvhostuser ports in a bi-directional
> + VM loopback as shown below, spreading the workload over 2 or 4 pmd
> + threads shows significant improvements as there will be more total CPU
> + occupancy available.
> +
> + NIC port0 <-> OVS <-> VM <-> OVS <-> NIC port 1
> +
> +### 4.3 DPDK port Rx Queues
> +
> + `ovs-vsctl set Interface <DPDK interface> options:n_rxq=<integer>`
> +
> + The command above sets the number of rx queues for DPDK interface.
> + The rx queues are assigned to pmd threads on the same NUMA node in a
> + round-robin fashion. For more information, please refer to the
> + Open_vSwitch TABLE section in
> +
> + `man ovs-vswitchd.conf.db`
> +
> +### 4.4 Exact Match Cache
> +
> + Each pmd thread contains one EMC. After initial flow setup in the
> + datapath, the EMC contains a single table and provides the lowest level
> + (fastest) switching for DPDK ports. If there is a miss in the EMC then
> + the next level where switching will occur is the datapath classifier.
> + Missing in the EMC and looking up in the datapath classifier incurs a
> + significant performance penalty. If lookup misses occur in the EMC
> + because it is too small to handle the number of flows, its size can
> + be increased. The EMC size can be modified by editing the define
> + EM_FLOW_HASH_SHIFT in lib/dpif-netdev.c.
> +
> + As mentioned above an EMC is per pmd thread. So an alternative way of
> + increasing the aggregate amount of possible flow entries in EMC and
> + avoiding datapath classifier lookups is to have multiple pmd threads
> + running. This can be done as described in section 4.2.
> +
> +### 4.5 Rx Mergeable buffers
> +
> + Rx Mergeable buffers is a virtio feature that allows chaining of multiple
> + virtio descriptors to handle large packet sizes. As such, large packets
> + are handled by reserving and chaining multiple free descriptors
> + together. Mergeable buffer support is negotiated between the virtio
> + driver and virtio device and is supported by the DPDK vhost library.
> + This behavior is typically supported and enabled by default, however
> + in the case where the user knows that rx mergeable buffers are not needed
> + i.e. jumbo frames are not needed, it can be forced off by adding
> + mrg_rxbuf=off to the QEMU command line options. By not reserving multiple
> + chains of descriptors it will make more individual virtio descriptors
> + available for rx to the guest using dpdkvhost ports and this can improve
> + performance.
> +
> +## <a name="ovstc"></a> 5. OVS Testcases
> +### 5.1 PHY-VM-PHY [VHOST LOOPBACK]
> +
> +The section 5.2 in INSTALL.DPDK guide lists steps for PVP loopback testcase
> +and packet forwarding using DPDK testpmd application in the Guest VM.
> +For users wanting to do packet forwarding using kernel stack below are the steps.
> +
> + ```
> + ifconfig eth1 1.1.1.2/24
> + ifconfig eth2 1.1.2.2/24
> + systemctl stop firewalld.service
> + systemctl stop iptables.service
> + sysctl -w net.ipv4.ip_forward=1
> + sysctl -w net.ipv4.conf.all.rp_filter=0
> + sysctl -w net.ipv4.conf.eth1.rp_filter=0
> + sysctl -w net.ipv4.conf.eth2.rp_filter=0
> + route add -net 1.1.2.0/24 eth2
> + route add -net 1.1.1.0/24 eth1
> + arp -s 1.1.2.99 DE:AD:BE:EF:CA:FE
> + arp -s 1.1.1.99 DE:AD:BE:EF:CA:EE
> + ```
> +
> +### 5.2 PHY-VM-PHY [IVSHMEM]
> +
> +IVSHMEM works only with 1GB huge pages.
IVSHMEM will not work with 2MG huge pages. It will work only...
> +
> + The steps (1-5) in 3.3 section of INSTALL.DPDK guide will create & initialize DB,
> + start vswitchd and add dpdk devices to bridge br0.
> +
> + 1. Add DPDK ring port to the bridge
> +
> + ```
> + ovs-vsctl add-port br0 dpdkr0 -- set Interface dpdkr0 type=dpdkr
> + ```
> +
> + 2. Copy runtime configuration to VM, To achieve this copy the files to a temporary
> + directory, say /tmp/rte_config and export the directory to the VM
> +
> + ```
> + mkdir /tmp/rte_config
> + chmod 644 /tmp/rte_config
> + cp -a /run/.rte_config /run/.rte_hugepage_info /tmp/rte_config
> + ```
> +
> + 3. Build modified Qemu
> +
> + ```
> + cd /usr/src/
> + wget https://github.com/01org/dpdk-ovs/archive/development.zip
> + unzip development.zip
> + cd dpdk-ovs-development/qemu
> + ./configure --target-list=x86_64-softmmu --enable-debug --extra-cflags='-g'
> + make -j 4
> + ```
> +
> + 4. start Guest VM
> +
> + ```
> + export VM_NAME=ivshmem-vm
> + export QCOW2_IMAGE=CentOS7_x86_64.qcow2
> + export QEMU_BIN=/usr/src/dpdk-ovs-development/qemu/x86_64-softmmu/qemu-system-x86_64
> +
> + taskset 0x20 $QEMU_BIN -cpu host -smp 2,cores=2 -hda $QCOW2_IMAGE -drive file=fat:rw:/tmp/rte_config,snapshot=off -m 4096M --enable-kvm -name $VM_NAME -nographic -vnc :2 -pidfile /tmp/vm1.pid -mem-path /dev/hugepages -mem-prealloc -device ivshmem,size=1024M,shm=fd:/dev/hugepages/rtemap_0:0x0:0x40000000
> + ```
> +
> + 5. Running sample "dpdk ring" app in VM
> +
> + ```
> + umount /dev/hugepages
> + mount -t hugetlbfs hugetlbfs /mnt/hugepages
> + ln -s /sys/devices/pci0000:00/0000:00:04.0/resource2 /dev/hugepages/rtemap_0
> + mount -o iocharset=utf8 /dev/sdb1 /mnt/ovs
> + cp /mnt/ovs/.rte_config /run/.
> + cp /mnt/ovs/.rte_hugepage_info /run/.
> +
> + # Build the DPDK ring application in the VM
> + export RTE_SDK=/root/dpdk-16.04
> + export RTE_TARGET=x86_64-ivshmem-linuxapp-gcc
> + make
> +
> + # Run dpdkring application
> + ./build/dpdkr -c 1 -n 4 --proc-type=secondary -- -n 0
> + where "-n 0" refers to ring '0' i.e dpdkr0
> + ```
> +
> +## <a name="vhost"></a> 6. Vhost Walkthrough
> +
> +DPDK 16.04 supports two types of vhost:
> +1. vhost-user - enabled default
> +2. vhost-cuse - Legacy, disabled by default
> +
> +### 6.1 vhost-user
> +
> + - Prerequisites:
> +
> + QEMU version >= 2.2
> +
> + - Adding vhost-user ports to Switch
> +
> + Unlike DPDK ring ports, DPDK vhost-user ports can have arbitrary names,
> + except that forward and backward slashes are prohibited in the names.
> +
> + For vhost-user, the name of the port type is `dpdkvhostuser`
> +
> + ```
> + ovs-vsctl add-port br0 vhost-user-1 -- set Interface vhost-user-1
> + type=dpdkvhostuser
> + ```
> +
> + This action creates a socket located at
> + `/usr/local/var/run/openvswitch/vhost-user-1`, which you must provide
> + to your VM on the QEMU command line. More instructions on this can be
> + found in the next section "Adding vhost-user ports to VM"
> +
> + Note: If you wish for the vhost-user sockets to be created in a
> + sub-directory of `/usr/local/var/run/openvswitch`, you may specify
> + this directory in the ovsdb like so:
> +
> + `./utilities/ovs-vsctl --no-wait \
> + set Open_vSwitch . other_config:vhost-sock-dir=subdir`
> +
> + - Adding vhost-user ports to VM
> +
> + 1. Configure sockets
> +
> + Pass the following parameters to QEMU to attach a vhost-user device:
> +
> + ```
> + -chardev socket,id=char1,path=/usr/local/var/run/openvswitch/vhost-user-1
> + -netdev type=vhost-user,id=mynet1,chardev=char1,vhostforce
> + -device virtio-net-pci,mac=00:00:00:00:00:01,netdev=mynet1
> + ```
> +
> + where vhost-user-1 is the name of the vhost-user port added
> + to the switch.
> + Repeat the above parameters for multiple devices, changing the
> + chardev path and id as necessary. Note that a separate and different
> + chardev path needs to be specified for each vhost-user device. For
> + example you have a second vhost-user port named 'vhost-user-2', you
> + append your QEMU command line with an additional set of parameters:
> +
> + ```
> + -chardev socket,id=char2,path=/usr/local/var/run/openvswitch/vhost-user-2
> + -netdev type=vhost-user,id=mynet2,chardev=char2,vhostforce
> + -device virtio-net-pci,mac=00:00:00:00:00:02,netdev=mynet2
> + ```
> +
> + 2. Configure huge pages.
> +
> + QEMU must allocate the VM's memory on hugetlbfs. vhost-user ports access
> + a virtio-net device's virtual rings and packet buffers mapping the VM's
> + physical memory on hugetlbfs. To enable vhost-user ports to map the VM's
> + memory into their process address space, pass the following parameters
> + to QEMU:
> +
> + ```
> + -object memory-backend-file,id=mem,size=4096M,mem-path=/dev/hugepages,
> + share=on -numa node,memdev=mem -mem-prealloc
> + ```
> +
> + 3. Enable multiqueue support(OPTIONAL)
> +
> + The vhost-user interface must be configured in Open vSwitch with the
> + desired amount of queues with:
> +
> + ```
> + ovs-vsctl set Interface vhost-user-2 options:n_rxq=<requested queues>
> + ```
> +
> + QEMU needs to be configured as well.
> + The $q below should match the queues requested in OVS (if $q is more,
> + packets will not be received).
> + The $v is the number of vectors, which is '$q x 2 + 2'.
> +
> + ```
> + -chardev socket,id=char2,path=/usr/local/var/run/openvswitch/vhost-user-2
> + -netdev type=vhost-user,id=mynet2,chardev=char2,vhostforce,queues=$q
> + -device virtio-net-pci,mac=00:00:00:00:00:02,netdev=mynet2,mq=on,vectors=$v
> + ```
> +
> + If one wishes to use multiple queues for an interface in the guest, the
> + driver in the guest operating system must be configured to do so. It is
> + recommended that the number of queues configured be equal to '$q'.
> +
> + For example, this can be done for the Linux kernel virtio-net driver with:
> +
> + ```
> + ethtool -L <DEV> combined <$q>
> + ```
> + where `-L`: Changes the numbers of channels of the specified network device
> + and `combined`: Changes the number of multi-purpose channels.
> +
> +### 6.2 vhost-cuse
> +
> + - Prerequisites:
> +
> + QEMU version >= 2.2
> +
> + - Enable vhost-cuse support
> +
> + 1. Enable vhost cuse support in DPDK
> +
> + Set `CONFIG_RTE_LIBRTE_VHOST_USER=n` in config/common_linuxapp and follow the
> + steps in 2.2 section of INSTALL.DPDK guide to build DPDK with cuse support.
> + OVS will detect that DPDK has vhost-cuse libraries compiled and in turn will enable
> + support for it in the switch and disable vhost-user support.
> +
> + 2. Insert the Cuse module
> +
> + `modprobe cuse`
> +
> + 3. Build and insert the `eventfd_link` module
> +
> + ```
> + cd $DPDK_DIR/lib/librte_vhost/eventfd_link/
> + make
> + insmod $DPDK_DIR/lib/librte_vhost/eventfd_link.ko
> + ```
> +
> + - Adding vhost-cuse ports to Switch
> +
> + Unlike DPDK ring ports, DPDK vhost-cuse ports can have arbitrary names.
> + For vhost-cuse, the name of the port type is `dpdkvhostcuse`
> +
> + ```
> + ovs-vsctl add-port br0 vhost-cuse-1 -- set Interface vhost-cuse-1
> + type=dpdkvhostcuse
> + ```
> +
> + When attaching vhost-cuse ports to QEMU, the name provided during the
> + add-port operation must match the ifname parameter on the QEMU cmd line.
> +
> + - Adding vhost-cuse ports to VM
> +
> + vhost-cuse ports use a Linux* character device to communicate with QEMU.
> + By default it is set to `/dev/vhost-net`. It is possible to reuse this
> + standard device for DPDK vhost, which makes setup a little simpler but it
> + is better practice to specify an alternative character device in order to
> + avoid any conflicts if kernel vhost is to be used in parallel.
> +
> + 1. This step is only needed if using an alternative character device.
> +
> + ```
> + ./utilities/ovs-vsctl --no-wait set Open_vSwitch . \
> + other_config:cuse-dev-name=my-vhost-net
> + ```
> +
> + In the example above, the character device to be used will be
> + `/dev/my-vhost-net`.
> +
> + 2. In case of reusing kernel vhost character device, there would be conflict
> + user should remove it.
> +
> + `rm -rf /dev/vhost-net`
> +
> + 3. Configure virtio-net adapters
> +
> + The following parameters must be passed to the QEMU binary, repeat
> + the below parameters for multiple devices.
> +
> + ```
> + -netdev tap,id=<id>,script=no,downscript=no,ifname=<name>,vhost=on
> + -device virtio-net-pci,netdev=net1,mac=<mac>
> + ```
> +
> + The DPDK vhost library will negotiate its own features, so they
> + need not be passed in as command line params. Note that as offloads
> + are disabled this is the equivalent of setting
> +
> + `csum=off,gso=off,guest_tso4=off,guest_tso6=off,guest_ecn=off`
> +
> + When using an alternative character device, it must be explicitly
> + passed to QEMU using the `vhostfd` argument
> +
> + ```
> + -netdev tap,id=<id>,script=no,downscript=no,ifname=<name>,vhost=on,
> + vhostfd=<open_fd> -device virtio-net-pci,netdev=net1,mac=<mac>
> + ```
> +
> + The open file descriptor must be passed to QEMU running as a child
> + process. This could be done with a simple python script.
> +
> + ```
> + #!/usr/bin/python
> + fd = os.open("/dev/usvhost", os.O_RDWR)
> + subprocess.call("qemu-system-x86_64 .... -netdev tap,id=vhostnet0,\
> + vhost=on,vhostfd=" + fd +"...", shell=True)
> + ```
> +
> + 4. Configure huge pages
> +
> + QEMU must allocate the VM's memory on hugetlbfs. Vhost ports access a
> + virtio-net device's virtual rings and packet buffers mapping the VM's
> + physical memory on hugetlbfs. To enable vhost-ports to map the VM's
> + memory into their process address space, pass the following parameters
> + to QEMU
> +
> + `-object memory-backend-file,id=mem,size=4096M,mem-path=/dev/hugepages,
> + share=on -numa node,memdev=mem -mem-prealloc`
> +
> + - VM Configuration with QEMU wrapper
> +
> + The QEMU wrapper script automatically detects and calls QEMU with the
> + necessary parameters. It performs the following actions:
> +
> + * Automatically detects the location of the hugetlbfs and inserts this
> + into the command line parameters.
> + * Automatically open file descriptors for each virtio-net device and
> + inserts this into the command line parameters.
> + * Calls QEMU passing both the command line parameters passed to the
> + script itself and those it has auto-detected.
> +
> + Before use, you **must** edit the configuration parameters section of the
> + script to point to the correct emulator location and set additional
> + settings. Of these settings, `emul_path` and `us_vhost_path` **must** be
> + set. All other settings are optional.
> +
> + To use directly from the command line simply pass the wrapper some of the
> + QEMU parameters: it will configure the rest. For example:
> +
> + ```
> + qemu-wrap.py -cpu host -boot c -hda <disk image> -m 4096 -smp 4
> + --enable-kvm -nographic -vnc none -net none -netdev tap,id=net1,
> + script=no,downscript=no,ifname=if1,vhost=on -device virtio-net-pci,
> + netdev=net1,mac=00:00:00:00:00:01
> + ```
> +
> + - VM Configuration with libvirt
> +
> + If you are using libvirt, you must enable libvirt to access the character
> + device by adding it to controllers cgroup for libvirtd using the following
> + steps.
> +
> + 1. In `/etc/libvirt/qemu.conf` add/edit the following lines:
> +
> + ```
> + clear_emulator_capabilities = 0
> + user = "root"
> + group = "root"
> + cgroup_device_acl = [
> + "/dev/null", "/dev/full", "/dev/zero",
> + "/dev/random", "/dev/urandom",
> + "/dev/ptmx", "/dev/kvm", "/dev/kqemu",
> + "/dev/rtc", "/dev/hpet", "/dev/net/tun",
> + "/dev/<my-vhost-device>",
> + "/dev/hugepages"]
> + ```
> +
> + <my-vhost-device> refers to "vhost-net" if using the `/dev/vhost-net`
> + device. If you have specificed a different name in the database
> + using the "other_config:cuse-dev-name" parameter, please specify that
> + filename instead.
> +
> + 2. Disable SELinux or set to permissive mode
> +
> + 3. Restart the libvirtd process
> + For example, on Fedora:
> +
> + `systemctl restart libvirtd.service`
> +
> + After successfully editing the configuration, you may launch your
> + vhost-enabled VM. The XML describing the VM can be configured like so
> + within the <qemu:commandline> section:
> +
> + 1. Set up shared hugepages:
> +
> + ```
> + <qemu:arg value='-object'/>
> + <qemu:arg value='memory-backend-file,id=mem,size=4096M,mem-path=/dev/hugepages,share=on'/>
> + <qemu:arg value='-numa'/>
> + <qemu:arg value='node,memdev=mem'/>
> + <qemu:arg value='-mem-prealloc'/>
> + ```
> +
> + 2. Set up your tap devices:
> +
> + ```
> + <qemu:arg value='-netdev'/>
> + <qemu:arg value='type=tap,id=net1,script=no,downscript=no,ifname=vhost0,vhost=on'/>
> + <qemu:arg value='-device'/>
> + <qemu:arg value='virtio-net-pci,netdev=net1,mac=00:00:00:00:00:01'/>
> + ```
> +
> + Repeat for as many devices as are desired, modifying the id, ifname
> + and mac as necessary.
> +
> + Again, if you are using an alternative character device (other than
> + `/dev/vhost-net`), please specify the file descriptor like so:
> +
> + `<qemu:arg value='type=tap,id=net3,script=no,downscript=no,ifname=vhost0,vhost=on,vhostfd=<open_fd>'/>`
> +
> + Where <open_fd> refers to the open file descriptor of the character device.
> + Instructions of how to retrieve the file descriptor can be found in the
> + "DPDK vhost VM configuration" section.
> + Alternatively, the process is automated with the qemu-wrap.py script,
> + detailed in the next section.
> +
> + Now you may launch your VM using virt-manager, or like so:
> +
> + `virsh create my_vhost_vm.xml`
> +
> + - VM Configuration with libvirt & QEMU wrapper
> +
> + To use the qemu-wrapper script in conjuntion with libvirt, follow the
> + steps in the previous section before proceeding with the following steps:
> +
> + 1. Place `qemu-wrap.py` in libvirtd binary search PATH ($PATH)
> + Ideally in the same directory that the QEMU binary is located.
> +
> + 2. Ensure that the script has the same owner/group and file permissions
> + as the QEMU binary.
> +
> + 3. Update the VM xml file using "virsh edit VM.xml"
> +
> + Set the VM to use the launch script.
> + Set the emulator path contained in the `<emulator><emulator/>` tags.
> + For example, replace `<emulator>/usr/bin/qemu-kvm<emulator/>` with
> + `<emulator>/usr/bin/qemu-wrap.py<emulator/>`
> +
> + 4. Edit the Configuration Parameters section of the script to point to
> + the correct emulator location and set any additional options. If you are
> + using a alternative character device name, please set "us_vhost_path" to the
> + location of that device. The script will automatically detect and insert
> + the correct "vhostfd" value in the QEMU command line arguments.
> +
> + 5. Use virt-manager to launch the VM
> +
> +### 6.3 DPDK backend inside VM
> +
> + Please note that additional configuration is required if you want to run
> + ovs-vswitchd with DPDK backend inside a QEMU virtual machine. Ovs-vswitchd
> + creates separate DPDK TX queues for each CPU core available. This operation
> + fails inside QEMU virtual machine because, by default, VirtIO NIC provided
> + to the guest is configured to support only single TX queue and single RX
> + queue. To change this behavior, you need to turn on 'mq' (multiqueue)
> + property of all virtio-net-pci devices emulated by QEMU and used by DPDK.
Add the following comment.
May not work with some old versions of Qemu found in some distros.
Requires Qemu version >= 2.x.
> + You may do it manually (by changing QEMU command line) or, if you use Libvirt,
> + by adding the following string:
> +
> + `<driver name='vhost' queues='N'/>`
> +
> + to <interface> sections of all network devices used by DPDK. Parameter 'N'
> + determines how many queues can be used by the guest.
> +
> +## <a name="qos"></a> 7. QOS
> +
> +Here is an example on QOS usage.
> +Assuming you have a vhost-user port transmitting traffic consisting of
> +packets of size 64 bytes, the following command would limit the egress
> +transmission rate of the port to ~1,000,000 packets per second
> +
> +`ovs-vsctl set port vhost-user0 qos=@newqos -- --id=@newqos create qos
> +type=egress-policer other-config:cir=46000000 other-config:cbs=2048`
> +
> +To examine the QoS configuration of the port:
> +
> +`ovs-appctl -t ovs-vswitchd qos/show vhost-user0`
> +
> +To clear the QoS configuration from the port and ovsdb use the following:
> +
> +`ovs-vsctl destroy QoS vhost-user0 -- clear Port vhost-user0 qos`
> +
> +For more details regarding egress-policer parameters please refer to the
> +vswitch.xml.
> +
> +## <a name="staticanalyzer"></a> 8. Static Code Analysis
> +
> +Static Analysis is method of debugging SW by examining the code rather than
> +actually executing it. Many third party Software is available to carry
> +Static analysis, few being open source and rest commercial.
> +
> +Below are the steps to run clang static analyzer on OVS codebase.
> +
> + ```
> + apt-get install clang [ On Ubuntu]
> + dnf install clang clang-analyzer -y [ On fedora]
> +
> + cd $OVS_DIR
> + ./boot.sh
> + ./configure --with-dpdk
> + make clean
> + scan-build make CFLAGS="-std=gnu99"
> + scan-view --host=<ip address> --port 8183 /tmp/scan-build-yyyy-mm-dd-114251-1027-1 --allow-all-hosts
> + ```
> +
> + The results can be viewed on the browser using ip address and port no.
> +
> + `http://<ip address>:8183/`
> +
> +## <a name="vsperf"></a> 9. Vsperf
> +
> +Vsperf project goal is to develop vSwitch test framework that can be used to
> +validate the suitability of different vSwitch implementations in a Telco deployment
> +environment. More information can be found in below link.
> +
> +https://wiki.opnfv.org/display/vsperf/VSperf+Home
> +
> +
> +Bug Reporting:
> +--------------
> +
> +Please report problems to bugs at openvswitch.org.
> +
> +
> +[INSTALL.userspace.md]:INSTALL.userspace.md
> +[INSTALL.md]:INSTALL.md
> +[DPDK Linux GSG]: http://www.dpdk.org/doc/guides/linux_gsg/build_dpdk.html#binding-and-unbinding-network-ports-to-from-the-igb-uioor-vfio-modules
> +[DPDK Docs]: http://dpdk.org/doc
>
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