Monday, December 21, 2015

[Django] The question of changing urlpattern dynamically

A couple of days my colleague gave me a quesiont about how to  change urlpattern dynamically in Django. Well, I indeed take some time to survey the way to do so even though we figure out alternatives to achieve the same result that we want. So, the following list is about the solution:
I perfer to adopt using middleware class to resolve this problem as follows:

An alternative method would be to either create a super pattern that calls a view, which in turn makes a DB call. Another approach is to handle this in a middleware class where you test for a 404 error, check if the pattern is likely to be one of your categories, and then do the DB look up there. I have done this in the past and it's not as bad as it sounds. Look at the django/contrib/flatpages code for a straightforward implementation of this approach.

For how to use middleware class, there is another link for the reference.

Thursday, December 17, 2015

[IOMMU] The error of "VFIO group is not viable"

As my previous article mentioned, DPDK is a library to accelerate packet transmission between user space application and physical network device. Recently there is an article "Using Open vSwitch 2.4 with DPDK-2.2.0 for Inter-VM NFV Applications" that aspires me to do the similiar test environment to witness how powerful DPDK is.
But, I enounter the error of "VFIO group is not viable" when I start openvswitch daemon. After searching the information on Google, it is related with IOMMU Group issue as described below:
Question 1:

I get the following error when attempting to start the guest:
vfio: error, group $GROUP is not viable, please ensure all devices within the iommu_group are bound to their vfio bus driver.

There are more devices in the IOMMU group than you're assigning, they all need to be bound to the vfio bus driver (vfio-pci) or pci-stub for the group to be viable.  See my previous post about IOMMU groups for more information.  To reduce the size of the IOMMU group, install the device into a different slot, try a platform that has better isolation support, or (at your own risk) bypass ACS using the ACS override patch.

So, the solutions are these two:
1. Install the device into a different slot
2. Bypass ACS using the ACS overrides patch

For the more explanation in details, you could see this article:

The following Scripts are the summary from the article:

# Update Grub
GRUB_CMDLINE_LINUX_DEFAULT="... default_hugepagesz=1G hugepagesz=1G hugepages=16 hugepagesz=2M hugepages=2048 iommu=pt intel_iommu=on isolcpus=1-13,15-27"

# Export Variables
export OVS_DIR=/root/soucecode/ovs
export DPDK_DIR=/root/soucecode/dpdk-2.1.0
export LC_ALL=en_US.UTF-8
export LANG=en_US.UTF-8
locale-gen "en_US.UTF-8"
dpkg-reconfigure locales

# build DPDK
curl -O
tar -xvzf dpdk-2.1.0.tar.gz
make install T=x86_64-ivshmem-linuxapp-gcc
cd $DPDK_DIR/x86_64-ivshmem-linuxapp-gcc
EXTRA_CFLAGS="-g -Ofast" make -j10

# build OVS
git clone
./configure --with-dpdk="$DPDK_DIR/x86_64-ivshmem-linuxapp-gcc/" CFLAGS="-g -Ofast"
make 'CFLAGS=-g -Ofast -march=native' -j10

# Setup OVS
pkill -9 ovs
rm -rf /usr/local/var/run/openvswitch
rm -rf /usr/local/etc/openvswitch/
rm -f /usr/local/etc/openvswitch/conf.db
mkdir -p /usr/local/etc/openvswitch
mkdir -p /usr/local/var/run/openvswitch
./ovsdb/ovsdb-tool create /usr/local/etc/openvswitch/conf.db ./vswitchd/vswitch.ovsschema
./ovsdb/ovsdb-server --remote=punix:/usr/local/var/run/openvswitch/db.sock --remote=db:Open_vSwitch,Open_vSwitch,manager_options --pidfile --detach
./utilities/ovs-vsctl --no-wait init

# Check IOMMU & Huge info
cat /proc/cmdline
grep Huge /proc/meminfo

# Setup Hugetable
mkdir -p /mnt/huge
mkdir -p /mnt/huge_2mb
mount -t hugetlbfs hugetlbfs /mnt/huge
mount -t hugetlbfs none /mnt/huge_2mb -o pagesize=2MB
# Bind Ether card
modprobe vfio-pci
cd $DPDK_DIR/tools
./ --status
./ --bind=vfio-pci 08:00.2

# Start OVS
modprobe openvswitch
$OVS_DIR/vswitchd/ovs-vswitchd --dpdk -c 0x2 -n 4 --socket-mem 2048 -- unix:/usr/local/var/run/openvswitch/db.sock --pidfile --detach

# Setup dpdk vhost user port
$OVS_DIR/utilities/ovs-vsctl show
$OVS_DIR/utilities/ovs-vsctl add-br br0 -- set bridge br0 datapath_type=netdev
$OVS_DIR/utilities/ovs-vsctl add-port br0 dpdk0 -- set Interface dpdk0 type=dpdk
$OVS_DIR/utilities/ovs-vsctl add-port br0 vhost-user1 -- set Interface vhost-user1 type=dpdkvhostuser
$OVS_DIR/utilities/ovs-vsctl add-port br0 vhost-user2 -- set Interface vhost-user2 type=dpdkvhostuser

find /sys/kernel/iommu_groups/ -type l

# Create VMs
qemu-system-x86_64 -m 1024 -smp 4 -cpu host -hda /tmp/vm1.qcow2 -boot c -enable-kvm -no-reboot -nographic -net none \
-chardev socket,id=char1,path=/usr/local/var/run/openvswitch/vhost-user1 \
-netdev type=vhost-user,id=mynet1,chardev=char1,vhostforce \
-device virtio-net-pci,mac=00:00:00:00:dd:01,netdev=mynet1 \
-object memory-backend-file,id=mem,size=1024M,mem-path=/dev/hugepages,share=on \
-numa node,memdev=mem -mem-prealloc
qemu-system-x86_64 -m 1024 -smp 4 -cpu host -hda /tmp/vm2.qcow2 -boot c -enable-kvm -no-reboot -nographic -net none \
-chardev socket,id=char1,path=/usr/local/var/run/openvswitch/vhost-user2 \
-netdev type=vhost-user,id=mynet1,chardev=char1,vhostforce \
-device virtio-net-pci,mac=00:00:00:00:dd:02,netdev=mynet1 \
-object memory-backend-file,id=mem,size=1024M,mem-path=/dev/hugepages,share=on \
-numa node,memdev=mem -mem-prealloc