Xen limit incoming traffic speed

Question

I've tried using 'rate' to limit the traffic speed of a VM inside the config file but that only limits the outgoing traffic speed of traffic from the VM. I want to limit the speed traffic can flow both ways.

Thanks

@silviud I use the 'limit' setting in the Xen VM config file. — Joel Kennedy, Apr 18 '11 at 23:40

score 1 · Answer 1 · answered Apr 27 '11 at 18:37

While I'm not sure of a way to limit the inbound traffic to a Xen DomU (which is actually what you claim to have already done), I have limited outbound traffic in the past by making a very simple change to the vif definition in my DomU's config file. For example, for one guest, I am using:

vif = [ 'rate=5Mb/s , bridge=xenbr0' ]

Like I said, though, this will only limit the rate of outbound traffic.

I've also read (but haven't tried) that you have the option of specifying a time window to tweak the latency/throughput, as well, with a syntax like the following:

vif = [ 'rate=5Mb/s@25ms , bridge=xenbr0' ]

Reference: http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/Virtualization/sect-Virtualization-Tips_and_tricks-Limit_network_bandwidth_for_a_Xen_guest.html

You are right - rate limits outbound, not inbound. I corrected the question. — Nils, Feb 04 '19 at 16:19

score 0 · Accepted Answer · edited Jul 07 '13 at 22:53

I use XEN 4.2.2 at the time of this reply.

Remove rate=X from your guest config file and shut it down.
Make sure your kernel have at least the following enabled:
IP: advanced router
TCP: advanced congestion control (all options enabled)
QoS and/or fair queueing (all options enabled expect the debug ones)
Install 'tc' command
Verify it's working by running: tc -s qdisc ls dev eth0

If you get no errors, you're ready to modify /etc/xen/scripts/vif-bridge

Find this word 'online)'

Just add before ;;

tc qdisc add dev "$dev" root tbf rate 120mbit burst 20mbit latency 5ms peakrate 125mbit minburst 20mbit mpu 64

So the modified version of vif-bridge should look like this:

online)        
        setup_virtual_bridge_port "$dev"

        mtu="`ip link show $bridge | awk '/mtu/ { print $5 }'`"

        if [ -n "$mtu" ] && [ "$mtu" -gt 0 ]

        then

                ip link set $dev mtu $mtu || :

        fi         

        add_to_bridge "$bridge" "$dev"

        tc qdisc add dev "$dev" root tbf rate 120mbit burst 20mbit latency 5ms peakrate 125mbit minburst 20mbit mpu 64

        ;;

Find this word 'offline)'

Append to first line: do_without_error tc qdisc del dev "$dev" root

offline)
        do_without_error tc qdisc del dev "$dev" root

        do_without_error brctl delif "$bridge" "$dev"

        do_without_error ifconfig "$dev" down

        ;;

Using the above TBF rule your guest should have roughly 12.5MB/s upload and 14.0M/s download speed; a bit over 120Mbps

If you upload/download same time, both upload and download speed should be about 7.5MB/s ~ 150Mbps total bandwidth

This is what I got after an hour tweaking. If you find better values; please let us know

Xen limit incoming traffic speed

2 Answers2