Re: Turning on TC throttles my HTTP downloads for no known reason

[Andy Furniss <andyqos@ukfsn.org>]

Alan McKay wrote:

> So I turned that off and immediately it fixed my problem!  Fantastic!
>   I then added that setting to post-up in /etc/network/interfaces on my
> Ubuntu 12.10 firewall, and restarted networking to test that it still
> worked.   And it did.   Great!
>
> Until I had to reboot my firewall (right where you see the big dip on
> that fixed graph).    After the reboot everything came up great and TC
> was enabled as expected, and this gro setting was still off as
> expected.   But my downloads were getting clobbered again and were in
> the 5 Mbit range.
>
> And as soon as I turned off TC they shoot back up again.

Strange - I would try turning gro on and off again when running to see 
if that helps and there is some timing issue with doing it at boot.

> I've reported all this to the shorewall list and everyone there seems stumped.
>
> Here is how Shorewall configures the TC on my eth0 (internet facing
> NIC on my firewall).    Some of the commands here are shorewallisms
> but I think this should still be pretty straightforward.
>
>          qt $TC qdisc del dev eth0 root
>          qt $TC qdisc del dev eth0 ingress
>          eth0_mtu=$(get_device_mtu eth0)
>          eth0_mtu1=$(get_device_mtu1 eth0)
>          run_tc qdisc add dev eth0 root handle 1: htb default 13 r2q 5
>          run_tc class add dev eth0 parent 1: classid 1:1 htb rate
> 1000kbit $eth0_mtu1
>          run_tc qdisc add dev eth0 handle ffff: ingress
>          run_tc filter add dev eth0 parent ffff: protocol all prio 10 basic \
>              police mpu 64 rate 35000kbit burst 10kb action drop

Another way to work around gro would be to use the mtu param for the 
policer try 3100 or may be bigger - I don't know how many packets get 
aggregated for you.

There is a potential problem with using protocol all in that you will be 
sending arp to potentially be dropped. If you are just shaping ipv4 then 
protocol ip would be better.

The same applies to using "htb default 13" though in this example having 
reasonable bandwidth and sfq on 13 will save the day.