Hi Mike,
Thanks for the patch - comments below.
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 the performance of the monitored port.
>
> It has been reported to reduce packet throughput significantly. I was
> able to reproduce a reduction in throughput of 70 percent with a very
> simple setup of two hosts communicating through a single bridge. This
> testing was performed on Linux both with and without the kernel module
> module loaded. Another more complex DPDK test was configured with the
> data path going from a port, through one OVS bridge, through a DPDK
> enabled network card, then into a different OVS bridge, and finally
> into another port.
>
> Using the dummy driver instead of a tunnel results in the following
> reduction in throughput compared to no ovs-tcpdump.
>
> Kernel datapath - 5%
> Usermode datapath - 10%
> DPDK datapath - 17%
What about before the dummy driver change? Can you add the numbers
pre/post this patch?
> Signed-off-by: Mike Pattrick <m...@redhat.com>
> ---
> utilities/ovs-tcpdump.in | 17 +++--------------
> 1 file changed, 3 insertions(+), 14 deletions(-)
>
> diff --git a/utilities/ovs-tcpdump.in b/utilities/ovs-tcpdump.in
> index 5ec02383c..9be39827e 100755
> --- a/utilities/ovs-tcpdump.in
> +++ b/utilities/ovs-tcpdump.in
> @@ -52,7 +52,6 @@ except Exception:
> print(" the correct location.")
> sys.exit(1)
>
> -tapdev_fd = None
> _make_taps = {}
> _make_mirror_name = {}
> IFNAMSIZ_LINUX = 15 # this is the max name size, excluding the null
> byte.
> @@ -68,20 +67,10 @@ def _doexec(*args, **kwargs):
>
>
> def _install_tap_linux(tap_name, mtu_value=None):
One nit - this function doesn't install a tap device any longer. Maybe
we should make it:
def _install_net_device_linux(dev_name, mtu_value=None):
WDYT?
Otherwise, looks fine to me.
> - """Uses /dev/net/tun to create a tap device"""
> - global tapdev_fd
> + _doexec(
> + *['ip', 'link', 'add', str(tap_name), 'type', 'dummy']
> + ).wait()
>
> - 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())
> -
> - 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',
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