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 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 resulted in the following impact to performance
compared to no ovs-tcpdump.
Kernel datapath - 5%
Usermode datapath - 10%
DPDK datapath - 17%
Signed-off-by: Mike Pattrick <m...@redhat.com>
---
utilities/ovs-tcpdump.in | 20 +++-----------------
1 file changed, 3 insertions(+), 17 deletions(-)
diff --git a/utilities/ovs-tcpdump.in b/utilities/ovs-tcpdump.in
index 5ec02383c..ee208f74a 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
@@ -52,7 +49,6 @@ 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 +64,10 @@ def _doexec(*args, **kwargs):
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())
+ _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',
--
2.30.2
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