ovs-benchmark(1) Open vSwitch Manual ovs-benchmark(1)
NAME
ovs-benchmark - flow setup benchmark utility for Open vSwitch
SYNOPSIS
ovs-benchmark latency --remote ip[:ports] [--sockets nsocks]
[--batches nbatches] [--local [ip][:ports]]
ovs-benchmark rate --remote ip[:ports] [--max-rate rate]
[--timeout maxsecs] [--sockets nsocks]
[--batches nbatches] [--local [ip][:ports]]
ovs-benchmark listen [--local [ip]:ports]
ovs-benchmark help
DESCRIPTION
ovs-benchmark tests the performance of Open vSwitch flow setup by set‐
ting up a number of TCP connections and measuring the time required.
It can also be used with the Linux bridge or without any bridging soft‐
ware, which allows one to measure the bandwidth and latency cost of
bridging.
Each ovs-benchmark command is described separately below.
The ``latency'' command
This command initiates nsocks TCP connections (by default, 100) as
quickly as possible, waits for each one to complete with success or
failure, and prints a bar chart of completion times on standard output,
followed by a summary line. Each line in the bar chart lists a time to
connection completion in milliseconds followed by a number of . or !
symbols, one for each TCP connection that completed in that many mil‐
liseconds. A successful connection prints a ., and an unsuccessful
connection (e.g. to a port on which no process is listening) prints a
!.
If nbatches is given, the entire procedure is repeated the specified
number of times. Only a single summary line is printed at the end.
Results vary widely based on the number of sockets and whether the
remote host is listening for connections on the specified ports. With
a small number of sockets, all connection times typically remain within
a handful of milliseconds. As the number of sockets increases, the
distribution of connection times clusters around the sending TCP
stack's SYN retransmission interval. (This pattern occurs with or
without Open vSwitch on the network path.)
The ``rate'' command
This command initiates nsocks TCP connections (by default, 100) as
quickly as possible (limited by maxrate, if --max-rate is specified).
Each time a connection completes with success or failure, it closes
that connection and initiates a new one. It continues to do so either
forever or, if --timeout is specified, until maxsecs seconds have
elapsed. During the test, it prints statistics about time elapsed,
successful and unsuccessful connections, and the average number of com‐
pleted (succeeded or failed) connections per second over the run.
Without --max-rate, the rate command measures the maximum sustained
flow setup rate for an Open vSwitch instance. This naturally tends to
drive ovs-vswitchd CPU usage to 100% on the host receiving the traffic.
When --max-rate is specified with a value below the maximum rate that
an Open vSwitch instance can handle, then rate can also be used to mea‐
sure the kernel and userspace CPU cost of flow setups at specific flow
rates.
Results tend to fluctuate greatly for the first few seconds of a run,
then settle down. The displayed average is calculated over the entire
run and so tends to converge asymptotically on the ``correct'' value.
To converge more quickly, try running for 5 to 10 seconds, then killing
and restarting the run.
The ``listen'' command
This command listens on one or more TCP ports for incoming connections.
It accepts connections and immediately closes them. It can be paired
with the rate or latency commands for observing effects of successful
vs. unsuccessful TCP connections.
It is easier to reproduce and interpret ovs-benchmark results when
there is no listener (see NOTES below).
The ``help'' command
Prints a usage message and exits successfully.
OPTIONS
-r ip[:ports]
--remote ip[:ports]
This option, required on latency and rate commands, minimally
specifies the remote host to connect to (as an IP address or DNS
name) as ip.
A TCP port or range of ports (separated by -) may also be speci‐
fied. If a range is specified then each port in the range is
used in round-robin order. The default port is 6630 if none is
specified.
-l [ip][:ports]
--local [ip][:ports]
On the latency and rate, without this option, outgoing connec‐
tions will not bind a specific TCP port. The local TCP stack
will pick a local TCP port to bind. When this option is speci‐
fied, the specified port or range of ports will be used in turn.
(If a port range is specified on both --local and --remote, then
each local port in its range will be used before the remote port
is incremented to the next port in its range.)
On the listen command, this option specifies the local port or
ports and IP addresses on which to listen. If it is omitted,
port 6630 on any IP address is used.
-s nsocks
--sockets nsocks
For latency, sets the number of connections to initiate per
batch. For rate, sets the number of outstanding connections
attempts to maintain at any given time. The default is 100.
-b nbatches
--batches nbatches
For latency, sets the number of times to initiate and wait for
all of the connections to complete. The default is 1.
-c maxrate
--max-rate maxrate
For rate, caps the maximum rate at which connections will be
attempted to maxrate connections per second. By default there
is no limit.
-T maxsecs
--timeout maxsecs
For rate, stops the benchmark after maxsecs seconds have
elapsed. By default, the benchmark continues until interrupted
by a signal.
NOTES
ovs-benchmark uses standard POSIX socket calls for network access, so
it shares the strengths and limitations of TCP/IP and its implementa‐
tions in the local and remote TCP/IP stacks. Particularly, TCP and its
implementations limit the number of successfully completed and then
closed TCP connections. This means that ovs-benchmark tests tend to
slow down if run for long intervals or with large numbers of sockets or
batches, if the remote system is listening on the port or ports being
contacted. The problem does not occur when the remote system is not
listening. ovs-benchmark results are therefore much more reliable and
repeatable when the remote system is not listening on the port or ports
being contacted. Even a single listening socket (e.g. range of ports
8000 to 9000 with one listener on port 8080) can cause anomalies in
results.
Be sure that the remote TCP/IP stack's firewall allows the benchmark's
traffic to be processed. For Open vSwitch benchmarking purposes, you
might want to disable the firewall with, e.g., iptables -F.
ovs-benchmark is single-threaded. A multithreaded process might be
able to initiate connections more quickly.
A TCP connection consists of two flows (one in each direction), so mul‐
tiply the TCP connection statistics that ovs-benchmark reports by 2 to
get flow statistics.
Open vSwitch 2.4.90 ovs-benchmark(1)