[Cake] Trouble getting decent performance with CAKE

jmarks2 at gmail.com jmarks2 at gmail.com
Wed Jan 27 12:49:29 EST 2021 

Thanks so much for getting back to me.
First, I am not so expert in these things, so please excuse my questions about providing the info you have requested and implementing your suggestions.

1. I don’t know what imq0 is used for, either. 
     I don't have a script to run CAKE at system start because I haven't got it working well enough. So, at reboot, the out-of-the box qdiscs are:

	qdisc ingress ffff: dev eth0 parent ffff:fff1 ----------------
	qdisc pfifo_fast 0: dev imq0 root refcnt 2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
	qdisc pfifo_fast 0: dev ifb0 root refcnt 2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1

     You can see that the imq0 device is present at startup. A quick search suggests that Ubiquiti uses this for native QOS during egress. If it's not clear what it's doing and if it's interfering, I will happily remove it, if I knew how. The worst that happens is that the system crashes and I have to reboot.

2. At startup (so no CAKE), sudo tc qdisc -s show:

	qdisc ingress ffff: dev eth0 parent ffff:fff1 ----------------
	 Sent 2055477419 bytes 2270158 pkt (dropped 0, overlimits 0 requeues 0)
	 backlog 0b 0p requeues 0

	qdisc pfifo_fast 0: dev imq0 root refcnt 2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
 	Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
 	backlog 0b 0p requeues 0

	qdisc pfifo_fast 0: dev ifb0 root refcnt 2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
	 Sent 2087261885 bytes 2270207 pkt (dropped 0, overlimits 0 requeues 1)
 	backlog 0b 0p requeues 1

3. I set up CAKE with the following commands:
	sudo tc qdisc add dev eth0 root handle 1:0 cake bandwidth...[switches]
	
	sudo set interfaces input ifb0
	sudo set interfaces ethernet eth0 redirect ifb0
	sudo tc qdisc add dev ifb0 root handle 2:0 cake bandwidth...[switches]

     Do these commands make CAKE the default, or can I choose a qdisc to use when running flent? If so, how do I do this?

4. Regarding your suggestion: "the download setting up tc mirred I assume you are doing with sqm? Do that."

     This is outside my knowledge, and I have not done anything like that.  
     I have read an alternative (older?) way to set up CAKE for ingress: 
	sudo ip link add name ifb4eth0 type ifb
	sudo tc qdisc del dev eth0 ingress
	sudo tc qdisc add dev eth0 handle ffff: ingress
	sudo tc qdisc del dev ifb4eth0 root
	sudo tc qdisc add dev ifb4eth0 root cake bandwidth...
	sudo ifconfig ifb4eth1 up
	sudo tc filter add dev eth1 parent ffff: protocol all prio 10 u32 match u32 0 0 flowid 1:1 action mirred egress redirect dev ifb4eth1

    I suspect the first 6 lines of this code achieve the same thing as the first two lines of code that I used (see point 3, above). Am I right?
    Is the filter that is specified in the last line what you are suggesting I add?

This is about as much as I can address with what you have suggested, without a super long email.

Please feel free to correct my mistakes in understanding.
If you have suggestions based on what I have written, I would so grateful. I am really looking forward to hearing what you think.
This learning curve is a little steep.

Many thanks.


-----Original Message-----
From: Dave Taht <dave.taht at gmail.com> 
Sent: Tuesday, January 26, 2021 11:19 PM
To: jmarks2 at gmail.com
Cc: Cake List <cake at lists.bufferbloat.net>
Subject: Re: [Cake] Trouble getting decent performance with CAKE

As much as I like to get the fustest with the mostest with the rrul test, it is often easier to test up and down separately.

do :

tc qdisc delete ifb0 root
tc qdisc delete eth0 root

I am not sure what imq is being used for....

Can you share the output of tc -s

instead?

a simple upload test would then be:

(unless you made cake the default)

flent -t pfifo_fast -H wherever --socket-stats -x --te=upload_streams=4 tcp_nup

tc qdisc add dev eth0 root cake all_your_options

flent -t cake -H wherever --socket-stats -x --te=upload_streams=4 tcp_nup

the download setting up tc mirred I assume you are doing with sqm? Do that.

flent -t -H wherever --socket-stats -x --te=download_streams=4 tcp_ndown

then send tc -s

It's entirely feasible your so-called 100mbit service is running at far far less than 100mbit in the first place.

Another thing to check is if your modem is connecting to the device at 100Mbit or a gbit. SOME - not enough - dsl modems actually connect at 100Mbit and/or joy of joys excert hw flow control.
95Mbit is gonna be slightly too high in former case for cake to control things, try 92mbit, or less.

On Tue, Jan 26, 2021 at 4:22 PM <jmarks2 at gmail.com> wrote:
>
> Dear CAKE experts,
>
> I write for your help in getting CAKE to perform on my router as I understand it should.
>
>
>
> I replaced my aging Asus home router with a Ubiquiti Edgerouter 4 specifically so I could take advantage of the port of CAKE to it.
>
>
>
> I am in the US, with VDSL2 service provided by AT&T at 100/20. I now have all unfiltered traffic delivered by the AT&T modem to the eth0 port on the router.
>
>
>
> My desktop runs Windows. So, to take advantage of flent to quantify CAKE performance, I stood up a Linux Mint VM and ran flent rrul tests before CAKE installation, and after.
>
>
>
> The first attached datafile, labeled qdisc pfifo fast, is the performance before CAKE. The other file, called 20/95 ack filtered bridged ptm, is my latest attempt with configuring CAKE flags.
>
> My major issue is with Ingress. Egress seems fine.
>
> For ingress, I see very little difference between performances with and without CAKE. And the overall throughput is far less than 100 mbit.
>
>
>
> The queuing disciplines on the router are:
>
>
>
> jeremymarks at ubnt:~$ sudo tc qdisc show
>
>
>
> qdisc cake 1: dev eth0 root refcnt 2 bandwidth 20Mbit besteffort 
> dual-srchost nat nowash ack-filter split-gso rtt 100.0ms ptm overhead 
> 22 no-sce
>
> qdisc ingress ffff: dev eth0 parent ffff:fff1 ----------------
>
> qdisc pfifo_fast 0: dev imq0 root refcnt 2 bands 3 priomap  1 2 2 2 1 
> 2 0 0 1 1 1 1 1 1 1 1
>
> qdisc cake 2: dev ifb0 root refcnt 2 bandwidth 95Mbit besteffort 
> dual-dsthost nat nowash ingress ack-filter split-gso rtt 100.0ms ptm 
> overhead 22 no-sce
>
>
>
> I must be making a major mistake in configuring CAKE.
>
>
>
> I would be grateful for any help or advice in getting this amazing program to work as it should.
>
>
>
> Many thanks for any help.
>
> Jeremy
>
>
>
>
>
> _______________________________________________
> Cake mailing list
> Cake at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/cake



--
"For a successful technology, reality must take precedence over public relations, for Mother Nature cannot be fooled" - Richard Feynman

dave at taht.net <Dave Täht> CTO, TekLibre, LLC Tel: 1-831-435-0729

More information about the Cake mailing list