qdisc pfifo 100: dev zhp0 limit 32p
The
tc
command is applied to a device, so
dev zhp0
must be specified. Note that a VLAN,
such as
zhp0
, and a port, such as
zre0
, are each treated as devices. Breakdown of the options:
handle 100:0
Defines the handle for the queuing discipline. This handle may be used to reference the pfifo
queue. Note that the handle is included with the output of the
qdisc ls
command.
(100:0 and 100: are equivalent in
tc
.) The choice of handle is significant for
zqosd
.
root
Tells
tc
that this is the base queuing discipline for the device, not a child of another queuing
discipline.
pfifo limit 32
Specifies a packet-limited FIFO queue with an upper bound of 32 packets.
Now, delete the queuing discipline from
zhp0
and confirm that it has been removed:
tc qdisc del dev zhp0 root
tc qdisc ls
Thus far,
tc
has been used without
zqosd
. It is not sufficient to install software rules on the
OpenArchitect switch though, because the normal case is for packets to be switched in hardware.
For that reason,
zqosd
must be used to shadow
tc
configuration into hardware. Like
zfilterd
,
zqosd
works with
ztmd
, which provides the actual hardware interaction.
If
ztmd
is not already running, start it:, then initiate the
zqosd
daemon with no parameters:
ztmd
zqosd
Now, repeat the same
tc
command as before, to install a packet-limited FIFO queue:
tc qdisc add dev zhp0 handle 100:0 root pfifo limit 32
When this command is processed,
zqosd
detects the state change and generates output.
For each port belonging to
zhp0
, the queue size has changed to 32 packets. Under the default
switch configuration, all ports other than the CPU port belong to
zhp0
; so all queues other than
the CPU queue are affected.
As before, remove the
tc
configuration with the command:
tc qdisc del dev zhp0 root
Note that
zqosd
detects this state change. In fact, examining the CoS configuration on the
switch reveals that the queue sizes have reverted to their default values.
Ethernet Switch Blade User's Guide
release 3.2.2j
page 66
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