Mike Pattrick <m...@redhat.com> writes:
> Currently the ovs-tcpdump utility creates a virtual tunnel to send
> packets to. This method functions perfectly fine, however, it can
> greatly impact performance of the monitored port.
>
> It has been reported to reduce packet throughput significantly. I was
> able to reproduce a reduction in throughput of up 70 percent in some
> tests with a simple setup of two hosts communicating through a single
> bridge on Linux with the kernel module datapath. Another more complex
> test was configured for DPDK and the usermode datapath. This test
> involved a data path going from a VM, through a port into one OVS
> bridge, out through a network card which could be DPDK enabled for the
> relevant tests, in to a different network interface, then into a
> different OVS bridge, through another port, and then into a virtual
> machine.
>
> Using the dummy driver resulted in the following impact to performance
> compared to no ovs-tcpdump. Due to intra-test variance and fluctuations
> during the first few seconds after installing a tap; multiple samples
> were taken over multiple test runs. The first few seconds worth of
> results were discarded and then results were averaged out.
>
> Original Script
> ===============
> Category Impact on Throughput
> Kernel datapath - 65%
> Usermode datapath - 26%
> DPDK datapath - 37%
>
> New Script
> ==========
> Category Impact on Throughput
> Kernel datapath - 5%
> Usermode datapath - 16%
> DPDK datapath - 29%
>
> Signed-off-by: Mike Pattrick <m...@redhat.com>
> ---
Looks good to me. Thanks for preserving the port teardown as well.
Acked-by: Aaron Conole <acon...@redhat.com>
> utilities/ovs-tcpdump.in | 42 +++++++++++++++++++++-------------------
> 1 file changed, 22 insertions(+), 20 deletions(-)
>
> diff --git a/utilities/ovs-tcpdump.in b/utilities/ovs-tcpdump.in
> index 5ec02383c..10989dfc1 100755
> --- a/utilities/ovs-tcpdump.in
> +++ b/utilities/ovs-tcpdump.in
> @@ -14,12 +14,9 @@
> # See the License for the specific language governing permissions and
> # limitations under the License.
>
> -import fcntl
> -
> import os
> import pwd
> from random import randint
> -import struct
> import subprocess
> import sys
> import time
> @@ -52,8 +49,8 @@ except Exception:
> print(" the correct location.")
> sys.exit(1)
>
> -tapdev_fd = None
> _make_taps = {}
> +_del_taps = {}
> _make_mirror_name = {}
> IFNAMSIZ_LINUX = 15 # this is the max name size, excluding the null
> byte.
>
> @@ -67,21 +64,11 @@ def _doexec(*args, **kwargs):
> return proc
>
>
> -def _install_tap_linux(tap_name, mtu_value=None):
> - """Uses /dev/net/tun to create a tap device"""
> - global tapdev_fd
> -
> - IFF_TAP = 0x0002
> - IFF_NO_PI = 0x1000
> - TUNSETIFF = 0x400454CA # This is derived by printf() of TUNSETIFF
> - TUNSETOWNER = TUNSETIFF + 2
> -
> - tapdev_fd = os.open('/dev/net/tun', os.O_RDWR)
> - ifr = struct.pack('16sH', tap_name.encode('utf8'), IFF_TAP | IFF_NO_PI)
> - fcntl.ioctl(tapdev_fd, TUNSETIFF, ifr)
> - fcntl.ioctl(tapdev_fd, TUNSETOWNER, os.getegid())
> +def _install_dst_if_linux(tap_name, mtu_value=None):
> + _doexec(
> + *['ip', 'link', 'add', str(tap_name), 'type', 'dummy']
> + ).wait()
>
> - time.sleep(1) # required to give the new device settling time
> if mtu_value is not None:
> pipe = _doexec(
> *(['ip', 'link', 'set', 'dev', str(tap_name), 'mtu',
> @@ -93,14 +80,22 @@ def _install_tap_linux(tap_name, mtu_value=None):
> pipe.wait()
>
>
> +def _remove_dst_if_linux(tap_name):
> + _doexec(
> + *['ip', 'link', 'del', str(tap_name)]
> + ).wait()
> +
> +
> def _make_linux_mirror_name(interface_name):
> if len(interface_name) > IFNAMSIZ_LINUX - 2:
> return "ovsmi%06d" % randint(1, 999999)
> return "mi%s" % interface_name
>
>
> -_make_taps['linux'] = _install_tap_linux
> -_make_taps['linux2'] = _install_tap_linux
> +_make_taps['linux'] = _install_dst_if_linux
> +_make_taps['linux2'] = _install_dst_if_linux
> +_del_taps['linux'] = _remove_dst_if_linux
> +_del_taps['linux2'] = _remove_dst_if_linux
> _make_mirror_name['linux'] = _make_linux_mirror_name
> _make_mirror_name['linux2'] = _make_linux_mirror_name
>
> @@ -455,6 +450,9 @@ def main():
> mirror_interface not in interfaces():
> _make_taps[sys.platform](mirror_interface,
> ovsdb.interface_mtu(interface))
> + tap_created = True
> + else:
> + tap_created = False
>
> if mirror_interface not in interfaces():
> print("ERROR: Please create an interface called `%s`" %
> @@ -480,6 +478,8 @@ def main():
> print("ERROR: Unable to properly setup the mirror: %s." % str(oe))
> try:
> ovsdb.destroy_port(mirror_interface,
> ovsdb.port_bridge(interface))
> + if tap_created is True:
> + _del_taps[sys.platform](mirror_interface)
> except Exception:
> pass
> sys.exit(1)
> @@ -498,6 +498,8 @@ def main():
>
> ovsdb.destroy_mirror(interface, ovsdb.port_bridge(interface))
> ovsdb.destroy_port(mirror_interface, ovsdb.port_bridge(interface))
> + if tap_created is True:
> + _del_taps[sys.platform](mirror_interface)
> except Exception:
> print("Unable to tear down the ports and mirrors.")
> print("Please use ovs-vsctl to remove the ports and mirrors
> created.")
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