X-Git-Url: http://git.cascardo.eti.br/?a=blobdiff_plain;f=INSTALL.DPDK.md;h=b33f75e3c0dcde940545cbc9e738ca848c273be3;hb=0bf765f753fd6cfde4918be49474fcd20659ceaa;hp=4c443e57cd3026cfd0f40b3e4e6889dfad0c0718;hpb=491c2ea3230f53ecbe65a556a0a1cc68647d7b99;p=cascardo%2Fovs.git diff --git a/INSTALL.DPDK.md b/INSTALL.DPDK.md index 4c443e57c..b33f75e3c 100644 --- a/INSTALL.DPDK.md +++ b/INSTALL.DPDK.md @@ -16,13 +16,15 @@ OVS needs a system with 1GB hugepages support. Building and Installing: ------------------------ -Required DPDK 1.7 +Required: DPDK 2.2 +Optional (if building with vhost-cuse): `fuse`, `fuse-devel` (`libfuse-dev` +on Debian/Ubuntu) 1. Configure build & install DPDK: 1. Set `$DPDK_DIR` ``` - export DPDK_DIR=/usr/src/dpdk-1.7.1 + export DPDK_DIR=/usr/src/dpdk-2.2 cd $DPDK_DIR ``` @@ -31,7 +33,7 @@ Required DPDK 1.7 `CONFIG_RTE_BUILD_COMBINE_LIBS=y` - Then run `make install` to build and isntall the library. + Then run `make install` to build and install the library. For default install without IVSHMEM: `make install T=x86_64-native-linuxapp-gcc` @@ -58,12 +60,14 @@ Required DPDK 1.7 `export DPDK_BUILD=$DPDK_DIR/x86_64-ivshmem-linuxapp-gcc/` ``` - cd $(OVS_DIR)/openvswitch + cd $(OVS_DIR)/ ./boot.sh - ./configure --with-dpdk=$DPDK_BUILD + ./configure --with-dpdk=$DPDK_BUILD [CFLAGS="-g -O2 -Wno-cast-align"] make ``` + Note: 'clang' users may specify the '-Wno-cast-align' flag to suppress DPDK cast-align warnings. + To have better performance one can enable aggressive compiler optimizations and use the special instructions(popcnt, crc32) that may not be available on all machines. Instead of typing `make`, type: @@ -90,7 +94,7 @@ Using the DPDK with ovs-vswitchd: 1. insert uio.ko: `modprobe uio` 2. insert igb_uio.ko: `insmod $DPDK_BUILD/kmod/igb_uio.ko` 3. Bind network device to igb_uio: - `$DPDK_DIR/tools/dpdk_nic_bind.py --bind=igb_uio eth1` + `$DPDK_DIR/tools/dpdk_nic_bind.py --bind=igb_uio eth1` * VFIO: @@ -101,9 +105,9 @@ Using the DPDK with ovs-vswitchd: 2. Set correct permissions on vfio device: `sudo /usr/bin/chmod a+x /dev/vfio` and: `sudo /usr/bin/chmod 0666 /dev/vfio/*` 3. Bind network device to vfio-pci: - `$DPDK_DIR/tools/dpdk_nic_bind.py --bind=vfio-pci eth1` + `$DPDK_DIR/tools/dpdk_nic_bind.py --bind=vfio-pci eth1` -3. Mount the hugetable filsystem +3. Mount the hugetable filesystem `mount -t hugetlbfs -o pagesize=1G none /dev/hugepages` @@ -158,15 +162,15 @@ Using the DPDK with ovs-vswitchd: ``` 6. Add bridge & ports - + To use ovs-vswitchd with DPDK, create a bridge with datapath_type "netdev" in the configuration database. For example: `ovs-vsctl add-br br0 -- set bridge br0 datapath_type=netdev` - Now you can add dpdk devices. OVS expect DPDK device name start with dpdk - and end with portid. vswitchd should print (in the log file) the number - of dpdk devices found. + Now you can add dpdk devices. OVS expects DPDK device names to start with + "dpdk" and end with a portid. vswitchd should print (in the log file) the + number of dpdk devices found. ``` ovs-vsctl add-port br0 dpdk0 -- set Interface dpdk0 type=dpdk @@ -177,6 +181,14 @@ Using the DPDK with ovs-vswitchd: polls dpdk device in continuous loop. Therefore CPU utilization for that thread is always 100%. + Note: creating bonds of DPDK interfaces is slightly different to creating + bonds of system interfaces. For DPDK, the interface type must be explicitly + set, for example: + + ``` + ovs-vsctl add-bond br0 dpdkbond dpdk0 dpdk1 -- set Interface dpdk0 type=dpdk -- set Interface dpdk1 type=dpdk + ``` + 7. Add test flows Test flow script across NICs (assuming ovs in /usr/src/ovs): @@ -195,55 +207,246 @@ Using the DPDK with ovs-vswitchd: ./ovs-ofctl add-flow br0 in_port=2,action=output:1 ``` -8. Performance tuning +8. QoS usage example - With pmd multi-threading support, OVS creates one pmd thread for each - numa node as default. The pmd thread handles the I/O of all DPDK - interfaces on the same numa node. The following two commands can be used - to configure the multi-threading behavior. + 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 Open_vSwitch . other_config:pmd-cpu-mask=` + `ovs-vsctl set port vhost-user0 qos=@newqos -- --id=@newqos create qos + type=egress-policer other-config:cir=46000000 other-config:cbs=2048` - The command above asks for a CPU mask for setting the affinity of pmd - threads. A set bit in the mask means a pmd thread is created and pinned - to the corresponding CPU core. For more information, please refer to - `man ovs-vswitchd.conf.db` + To examine the QoS configuration of the port: - `ovs-vsctl set Open_vSwitch . other_config:n-dpdk-rxqs=` + `ovs-appctl -t ovs-vswitchd qos/show vhost-user0` - The command above sets the number of rx queues of each DPDK interface. The - rx queues are assigned to pmd threads on the same numa node in round-robin - fashion. For more information, please refer to `man ovs-vswitchd.conf.db` + To clear the QoS configuration from the port and ovsdb use the following: - Ideally for maximum throughput, the pmd thread should not be scheduled out - which temporarily halts its execution. The following affinitization methods - can help. + `ovs-vsctl destroy QoS vhost-user0 -- clear Port vhost-user0 qos` - Lets pick core 4,6,8,10 for pmd threads to run on. Also assume a dual 8 core - sandy bridge system with hyperthreading enabled where CPU1 has cores 0,...,7 - and 16,...,23 & CPU2 cores 8,...,15 & 24,...,31. (A different cpu - configuration could have different core mask requirements). + For more details regarding egress-policer parameters please refer to the + vswitch.xml. - To kernel bootline add core isolation list for cores and associated hype cores - (e.g. isolcpus=4,20,6,22,8,24,10,26,). Reboot system for isolation to take - effect, restart everything. +Performance Tuning: +------------------- - Configure pmd threads on core 4,6,8,10 using 'pmd-cpu-mask': + 1. PMD affinitization - `ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=00000550` + A poll mode driver (pmd) thread handles the I/O of all DPDK + interfaces assigned to it. A pmd thread will busy loop through + the assigned port/rxq's polling for packets, switch the packets + and send to a tx port if required. Typically, it is found that + a pmd thread is CPU bound, meaning that the greater the CPU + occupancy the pmd thread can get, the better the performance. To + that end, it is good practice to ensure that a pmd thread has as + many cycles on a core available to it as possible. This can be + achieved by affinitizing the pmd thread with a core that has no + other workload. See section 7 below for a description of how to + isolate cores for this purpose also. - You should be able to check that pmd threads are pinned to the correct cores - via: + The following command can be used to specify the affinity of the + pmd thread(s). - ``` - top -p `pidof ovs-vswitchd` -H -d1 - ``` + `ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=` + + 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 1 + + `ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=2` + + For more information, please refer to the Open_vSwitch TABLE section in + + `man ovs-vswitchd.conf.db` + + Note, that a pmd thread on a NUMA node is only created if there is + at least one DPDK interface from that NUMA node added to OVS. + + 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. + + The following command can be used to specify the affinity of the + pmd threads. + + `ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=` + + 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 more information, please refer to the Open_vSwitch TABLE section in + + `man ovs-vswitchd.conf.db` + + 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 + + The following command can be used to confirm that the port/rxq assignment + to pmd threads is as required: + + `ovs-appctl dpif-netdev/pmd-rxq-show` + + This can also be checked with: + + ``` + top -H + taskset -p + ``` + + To understand where most of the pmd thread time is spent and whether the + caches are being utilized, these commands can be used: + + ``` + # Clear previous stats + ovs-appctl dpif-netdev/pmd-stats-clear + + # Check current stats + ovs-appctl dpif-netdev/pmd-stats-show + ``` + + 3. DPDK port Rx Queues + + `ovs-vsctl set Interface options:n_rxq=` + + 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. 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 2. + + 5. Compiler options + + The default compiler optimization level is '-O2'. Changing this to + more aggressive compiler optimizations such as '-O3' or + '-Ofast -march=native' with gcc can produce performance gains. + + 6. Simultaneous Multithreading (SMT) + + With SMT enabled, one physical core appears as two logical cores + which can improve performance. + + SMT can be utilized to add additional pmd threads without consuming + additional physical cores. Additional pmd threads may be added in the + same manner as described in section 2. If trying to minimize the use + of physical cores for pmd threads, 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. + + For example, when using 2x 10 core processors in a dual socket system + with HT enabled, /proc/cpuinfo will report 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` + + Note that SMT is enabled by the Hyper-Threading section in the + BIOS, and as such will apply to the whole system. So the impact of + enabling/disabling it for the whole system should be considered + e.g. If workloads on the system can scale across multiple cores, + SMT may very beneficial. However, if they do not and perform best + on a single physical core, SMT may not be beneficial. + + 7. The isolcpus kernel boot parameter + + isolcpus can be used on the kernel bootline to isolate cores from the + kernel scheduler and hence dedicate them to OVS or other packet + forwarding related workloads. For example a Linux kernel boot-line + could be: + + 'GRUB_CMDLINE_LINUX_DEFAULT="quiet hugepagesz=1G hugepages=4 default_hugepagesz=1G 'intel_iommu=off' isolcpus=1-19"' + + 8. 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. + + 9. 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. + + 10. Packet processing in the guest + + It is good practice whether simply forwarding packets from one + interface to another or more complex packet processing in the guest, + to ensure that the thread performing this work has as much CPU + occupancy as possible. For example when the DPDK sample application + `testpmd` is used to forward packets in the guest, multiple QEMU vCPU + threads can be created. Taskset can then be used to affinitize the + vCPU thread responsible for forwarding to a dedicated core not used + for other general processing on the host system. + + 11. DPDK virtio pmd in the guest + + dpdkvhostcuse or dpdkvhostuser ports can be used to accelerate the path + to the guest using the DPDK vhost library. This library is compatible with + virtio-net drivers in the guest but significantly better performance can + be observed when using the DPDK virtio pmd driver in the guest. The DPDK + `testpmd` application can be used in the guest as an example application + that forwards packet from one DPDK vhost port to another. An example of + running `testpmd` in the guest can be seen here. + + `./testpmd -c 0x3 -n 4 --socket-mem 512 -- --burst=64 -i --txqflags=0xf00 --disable-hw-vlan --forward-mode=io --auto-start` + + See below information on dpdkvhostcuse and dpdkvhostuser ports. + See [DPDK Docs] for more information on `testpmd`. - Note, the pmd threads on a numa node are only created if there is at least - one DPDK interface from the numa node that has been added to OVS. - Note, core 0 is always reserved from non-pmd threads and should never be set - in the cpu mask. DPDK Rings : ------------ @@ -290,18 +493,474 @@ A general rule of thumb for better performance is that the client application should not be assigned the same dpdk core mask "-c" as the vswitchd. +DPDK vhost: +----------- + +DPDK 2.2 supports two types of vhost: + +1. vhost-user +2. vhost-cuse + +Whatever type of vhost is enabled in the DPDK build specified, is the type +that will be enabled in OVS. By default, vhost-user is enabled in DPDK. +Therefore, unless vhost-cuse has been enabled in DPDK, vhost-user ports +will be enabled in OVS. +Please note that support for vhost-cuse is intended to be deprecated in OVS +in a future release. + +DPDK vhost-user: +---------------- + +The following sections describe the use of vhost-user 'dpdkvhostuser' ports +with OVS. + +DPDK vhost-user Prerequisites: +------------------------- + +1. DPDK 2.2 with vhost support enabled as documented in the "Building and + Installing section" + +2. QEMU version v2.1.0+ + + QEMU v2.1.0 will suffice, but it is recommended to use v2.2.0 if providing + your VM with memory greater than 1GB due to potential issues with memory + mapping larger areas. + +Adding DPDK vhost-user ports to the Switch: +-------------------------------------- + +Following the steps above to create a bridge, you can now add DPDK vhost-user +as a port to the vswitch. 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 "DPDK vhost-user VM configuration" + Note: If you wish for the vhost-user sockets to be created in a + directory other than `/usr/local/var/run/openvswitch`, you may specify + another location on the ovs-vswitchd command line like so: + + `./vswitchd/ovs-vswitchd --dpdk -vhost_sock_dir /my-dir -c 0x1 ...` + +DPDK vhost-user VM configuration: +--------------------------------- +Follow the steps below to attach vhost-user port(s) to a 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 paramters + to QEMU: + + ``` + -object memory-backend-file,id=mem,size=4096M,mem-path=/dev/hugepages, + share=on + -numa node,memdev=mem -mem-prealloc + ``` + +3. Optional: Enable multiqueue support + 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= + ``` + + 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 '$q'. + + For example, this can be done for the Linux kernel virtio-net driver with: + + ``` + ethtool -L combined <$q> + ``` + + A note on the command above: + + `-L`: Changes the numbers of channels of the specified network device + + `combined`: Changes the number of multi-purpose channels. + +DPDK vhost-cuse: +---------------- + +The following sections describe the use of vhost-cuse 'dpdkvhostcuse' ports +with OVS. + +DPDK vhost-cuse Prerequisites: +------------------------- + +1. DPDK 2.2 with vhost support enabled as documented in the "Building and + Installing section" + As an additional step, you must enable vhost-cuse in DPDK by setting the + following additional flag in `config/common_linuxapp`: + + `CONFIG_RTE_LIBRTE_VHOST_USER=n` + + Following this, rebuild DPDK as per the instructions in the "Building and + Installing" section. Finally, rebuild OVS as per step 3 in the "Building + and Installing" section - 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 + ``` + +4. QEMU version v2.1.0+ + + vhost-cuse will work with QEMU v2.1.0 and above, however it is recommended to + use v2.2.0 if providing your VM with memory greater than 1GB due to potential + issues with memory mapping larger areas. + Note: QEMU v1.6.2 will also work, with slightly different command line parameters, + which are specified later in this document. + +Adding DPDK vhost-cuse ports to the Switch: +-------------------------------------- + +Following the steps above to create a bridge, you can now add DPDK vhost-cuse +as a port to the vswitch. 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 command + line. More instructions on this can be found in the next section. + +DPDK vhost-cuse VM configuration: +--------------------------------- + + 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. + + The new character device filename must be specified on the vswitchd + commandline: + + `./vswitchd/ovs-vswitchd --dpdk --cuse_dev_name my-vhost-net -c 0x1 ...` + + Note that the `--cuse_dev_name` argument and associated string must be the first + arguments after `--dpdk` and come before the EAL arguments. In the example + above, the character device to be used will be `/dev/my-vhost-net`. + +2. This step is only needed if reusing the standard character device. It will + conflict with the kernel vhost character device so the user must first + remove it. + + `rm -rf /dev/vhost-net` + +3a. Configure virtio-net adaptors: + The following parameters must be passed to the QEMU binary: + + ``` + -netdev tap,id=,script=no,downscript=no,ifname=,vhost=on + -device virtio-net-pci,netdev=net1,mac= + ``` + + Repeat the above parameters for multiple devices. + + The DPDK vhost library will negiotiate 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` + +3b. If using an alternative character device. It must be also explicitly + passed to QEMU using the `vhostfd` argument: + + ``` + -netdev tap,id=,script=no,downscript=no,ifname=,vhost=on, + vhostfd= + -device virtio-net-pci,netdev=net1,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) + + Alternatively the `qemu-wrap.py` script can be used to automate the + requirements specified above and can be used in conjunction with libvirt if + desired. See the "DPDK vhost VM configuration with QEMU wrapper" section + below. + +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` + + Note: For use with an earlier QEMU version such as v1.6.2, use the + following to configure hugepages instead: + + `-mem-path /dev/hugepages -mem-prealloc` + +DPDK vhost-cuse 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 -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 +``` + +DPDK vhost-cuse 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: + + ``` + 1) clear_emulator_capabilities = 0 + 2) user = "root" + 3) group = "root" + 4) 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/", + "/dev/hugepages"] + ``` + + refers to "vhost-net" if using the `/dev/vhost-net` + device. If you have specificed a different name on the ovs-vswitchd + commandline using the "--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 section: + + 1. Set up shared hugepages: + + ``` + + + + + + ``` + + 2. Set up your tap devices: + + ``` + + + + + ``` + + 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: + + `` + + Where 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` + +DPDK vhost-cuse VM configuration with libvirt and 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's 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" + + 1. Set the VM to use the launch script. + Set the emulator path contained in the `` tags. + For example, replace: + + `/usr/bin/qemu-kvm` + + with: + + `/usr/bin/qemu-wrap.py` + + 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 + +Running ovs-vswitchd with DPDK backend inside a 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. +You may do it manually (by changing QEMU command line) or, if you use Libvirt, +by adding the following string: + +`` + +to sections of all network devices used by DPDK. Parameter 'N' +determines how many queues can be used by the guest. + Restrictions: ------------- - - This Support is for Physical NIC. I have tested with Intel NIC only. - Work with 1500 MTU, needs few changes in DPDK lib to fix this issue. - Currently DPDK port does not make use any offload functionality. + - DPDK-vHost support works with 1G huge pages. ivshmem: - - The shared memory is currently restricted to the use of a 1GB - huge pages. - - All huge pages are shared amongst the host, clients, virtual - machines etc. + - If you run Open vSwitch with smaller page sizes (e.g. 2MB), you may be + unable to share any rings or mempools with a virtual machine. + This is because the current implementation of ivshmem works by sharing + a single 1GB huge page from the host operating system to any guest + operating system through the Qemu ivshmem device. When using smaller + page sizes, multiple pages may be required to hold the ring descriptors + and buffer pools. The Qemu ivshmem device does not allow you to share + multiple file descriptors to the guest operating system. However, if you + want to share dpdkr rings with other processes on the host, you can do + this with smaller page sizes. + + Platform and Network Interface: + - By default with DPDK 2.2, a maximum of 64 TX queues can be used with an + Intel XL710 Network Interface on a platform with more than 64 logical + cores. If a user attempts to add an XL710 interface as a DPDK port type to + a system as described above, an error will be reported that initialization + failed for the 65th queue. OVS will then roll back to the previous + successful queue initialization and use that value as the total number of + TX queues available with queue locking. If a user wishes to use more than + 64 queues and avoid locking, then the + `CONFIG_RTE_LIBRTE_I40E_QUEUE_NUM_PER_PF` config parameter in DPDK must be + increased to the desired number of queues. Both DPDK and OVS must be + recompiled for this change to take effect. + + vHost and QEMU v2.4.0+: + - For versions of QEMU v2.4.0 and later, it is currently not possible to + unbind more than one dpdkvhostuser port from the guest kernel driver + without causing the ovs-vswitchd process to crash. If this is a requirement + for your use case, it is recommended either to use a version of QEMU + between v2.2.0 and v2.3.1 (inclusive), or alternatively, to apply the + following patch to DPDK and rebuild: + http://dpdk.org/dev/patchwork/patch/7736/ + This problem will likely be resolved in Open vSwitch at a later date, when + the next release of DPDK (which includes the above patch) is available and + integrated into OVS. Bug Reporting: -------------- @@ -311,3 +970,4 @@ Please report problems to bugs@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