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.bodire...@intel.com>
---
INSTALL.DPDK-ADVANCED.md | 809 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 809 insertions(+)
create mode 100644 INSTALL.DPDK-ADVANCED.md
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+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 b...@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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