5.put all together

This chapter will present how to put all the components together ,and make it work well.

1.first thing is make it clear how much memory we must preserve for the virtual link .

I would say,The maximum memory would be 1GB,i.e. 512 huge pages,the reason is simple:we must map the dpdk hugepage into guest device by qemu,the pci device memory limitation make it 1GB,so,is this possible for a virtual link to run well? the memory mapping facilitate packet rx\/tx between guest and host,so the memory which could be used for other purpose is limited,we address this limitation by making host dpdk huge pages memory exclusive for packets transmiting ,application should be aware of this ,and manage their own memory if necessary.

2.set up the environment for virtual link.

build the projects：

git clone https://github.com/chillancezen/vlinky2 and export this directory as VLINK_SDK ,and then change directory to $(VLINK_SDK)/vlinkinfra build and install vlink infrastructure library by make install, so we could also start up demo agent :make -C sample;./sample/bin/virt_compute so far ,the agent start to work for qemu and dpdk.

next build a eal-modified dpdk version git clone https://github.com/chillancezen/dpdk-16.07-vlink this projects will changed some code of eal and introducer a new PMD driver:eth_vlink<x>,link=<name>,mode=[bond|mq] ,build it as usual.

next also build a special version of qemu and a new pci device is introduced :-device pci-vlink,vm_domain=testvm1,init_config=./link.config,the initial config file has the following format:

tap123 00:12:23:34:45:56 3
tap456 00:12:23:34:45:57 5

the are name mac-address number-of-link,and the channel number should be number of data channels plus 1,the one is the ctrl channel.

note qemu side allocate virtual link ,and dpdk side attach to virtual link,so we define virtual link in the initial config script ,then start an instance use qemu ,a possible command parameter is presented as below: taskset -c 9-11 ./qemu-system-x86_64 --enable-kvm -m 2G -smp 6 -cpu host -hda mywork/centos.qcow2 -boot c -nographic -vnc :0 -netdev user,id=mynet0,net=192.168.76.0/24,dhcpstart=192.168.76.99 -device virtio-net-pci,netdev=mynet0 -redir tcp:2222::22 -device pci-vlink,vm_domain=testvm1,init_config=./link.config,next we can ssh into the virtual machine . through lspci ,we get :

[root@localhost ~(keystone_admin)]# lspci -vvv -nn -s 00:04.0
00:04.0 Ethernet controller [0200]: Catapult Communications Device [cccc:2222]
        Subsystem: Red Hat, Inc Device [1af4:1100]
        Physical Slot: 4
        Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
        Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Interrupt: pin B routed to IRQ 10
        Region 0: I/O ports at c000 [size=1K]
        Region 2: Memory at 80000000 (32-bit, prefetchable) [size=1G]
        Region 3: Memory at c1000000 (32-bit, prefetchable) [size=8M]

there are three regions in the pci device ,the 0 region is io port region ,driver could fetch information through io port read \/write ,this it common way to configure device or retrive information from devices.

next two regions are host dpdk huge page memory region and virtual link control channels memory, note that the whole host dpdk memory is mmaped into device ,the size is 1GB(even though virtual address spaces maybe not continuous with host dpdk context,here the these memory is physically continuous,we know how to translate address between different contexts,we describe this later.)which is rather large ,and rounded to 1GB even the real space is lower than 1GB(pci device memory size must be power of 2). the ctrl channel memory is place which hold and accommodate virt queues.it 's a little smaller .

next we will build a uio driver which takes over our virtual pci nic ,still clone the gt repo,https:\/\/github.com\/chillancezen\/vlinky2.git ,then export environment like this:declare -x VLINK_SDK="/root/vlinky2" ,then change pwd to $(VLINK_SDK)\/uio_vlink,their we will build the uio kernel driver by:

here we could find out what kernel driver in use. further more ,uio framework will generate a char device for every uio device under \/dev,now let's check that.

as a matter of fact ,there are lots of ways to access io ports and io memory resource in userspace ,if you are interested with uio device internals ,please refer to:http:\/\/nairobi-embedded.org\/category\/device-drivers.html which will give you a overview about how uio works. here I tend to probe my own uio device through \/sys filesystem.and then make these resource available .there are two kinds of resource :

1) io ports

io ports is system-wide ,even in user space ,it's so easy to read\/write them ,please refer to sys\/io.h .

2) io memory.

io memory must be remapped into process virtual address space ,there are usually two ways to do that : \/dev\/uioX mapping with certain offset ,and \/sys file mapping .both of which I will not detail here still.

here in my project ,a library can do all the thing ,it 's libvlinkguest.so,so let's change pwd to $(VLINK_SDK)\/vlinkguest, then still make;make install.

next come to librte_vlink which is a DPDK extension which regulates interface how to rx\/tx(not limited ) packet from\/to virtual links:

make the projects ,then goto $(VLINK_SDK)\/librte_vlink\/test ,build the test program, and then ,run the program which will start the loop to rx packets from virtual links and echo them back.

we probe two virtual links ,and before starting rx\/tx we setup translation table in two directions .

last step would be launching pktgen-dpdk and start generating flows ,we put qemu and dpdk-pktgen on the same numa node (aka.numa 1),also disable hyper-thread :

./app/app/x86_64-native-linuxapp-gcc/pktgen -c 1c0 --vdev=eth_vlink0,link=tap123,mode=mq -- P -T -f themes/black-yellow.theme -m '[7/8:7/8].0'

with 64-bytes packets ,we get this :

remember ,it's only two-channel virtual link,one one channel may share more than 10.5 Mpps through .one thing more ,the packet size impose same overhead on virtual links which is quite different from other PMD implementation .

still ,the throughput does not change at all because of zero-copy .

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