[Bloat] CAKE in openwrt high CPU

[Dave Taht]

cake reschedules too much compared to the tweaks we have to keep htb
fed, at these rates.

It was kind of my hope to gain a hw assist in future versions of the
apu series. a programmable completion interrupt is available in some
versions of that chipset,

On Sun, Aug 30, 2020 at 10:27 AM Mikael Abrahamsson via Bloat
<bloat at lists.bufferbloat.net> wrote:
>
>
> 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?
>
> --
> Mikael Abrahamsson    email: swmike at swm.pp.se
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> Bloat at lists.bufferbloat.net
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dave at taht.net <Dave Täht> CTO, TekLibre, LLC Tel: 1-831-435-0729