[Bloat] CAKE in openwrt high CPU

[Jonathan Foulkes]

Toke, that link returns a 404 for me.

For others, I’ve found that testing cake throughput with isolation options enabled is tricky if there are many competing connections. 
Like I keep having to tell my customers, fairness algorithms mean no one device will ever gain 100% of the bandwidth so long as there are other open & active connections from other devices.

That said, I’d love to find options to increase throughput for single-tin configs.

Cheers,

Jonathan

> On Aug 31, 2020, at 7:35 AM, Toke Høiland-Jørgensen via Bloat <bloat at lists.bufferbloat.net> wrote:
> 
> Mikael Abrahamsson via Bloat <bloat at lists.bufferbloat.net> writes:
> 
>> Hi,
>> 
>> I migrated to an APU2 (https://www.pcengines.ch/apu2.htm) as residential 
>> router, from my previous WRT1200AC (marvell armada 385).
>> 
>> I was running OpenWrt 18.06 on that one, now I am running latest 19.07.3 
>> on the APU2.
>> 
>> Before I had 500/100 and I had to use FQ_CODEL because CAKE took too much 
>> CPU to be able to do 500/100 on the WRT1200AC. Now I upgraded to 1000/1000 
>> and tried it again, and even the APU2 can only do CAKE up to ~300 
>> megabit/s. With FQ_CODEL I get full speed (configure 900/900 in SQM in 
>> OpenWrt).
>> 
>> Looking in top, I see sirq% sitting at 50% pegged. This is typical what I 
>> see when CPU based forwarding is maxed out. From my recollection of 
>> running CAKE on earlier versions of openwrt (17.x) I don't remember CAKE 
>> using more CPU than FQ_CODEL.
>> 
>> Anyone know what's up? I'm fine running FQ_CODEL, it solves any 
>> bufferbloat but... I thought CAKE supposedly should use less CPU, not 
>> more?
> 
> Hmm, you say CAKE and FQ-Codel - so you're not enabling the shaper (that
> would be FQ-CoDel+HTB)? An exact config might be useful (or just the
> output of tc -s qdisc).
> 
> If you are indeed not shaping, maybe you're hitting the issue fixed by this commit?
> 
> https://github.com/dtaht/sch_cake/commit/3152477235c934022049fcddc063c45d37ec10e6n
> 
> -Toke
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