[Bloat] CAKE in openwrt high CPU

[Sebastian Moeller]

Hi Mikael,

Thanks! That looks like a fully saturated core, no? I do not know how to parse the symbols here, so not sure what "class" of load is denoted by the star, but I would guess something including sirqs? Anyway the average is ~49% load, while clearly CPU is pegged already. I assume the htop data is from the HGW...

best regards
	Sebastian

> On Sep 4, 2020, at 15:37, Mikael Abrahamsson <swmike at swm.pp.se> wrote:
> 
> On Thu, 3 Sep 2020, Sebastian Moeller wrote:
> 
>> 	Mmmh, how did you measure the sirq percentage? Some top versions show overall percentage with 100% meaning all CPUs, so 35% in a quadcore could mean 1 fully maxed out CPU (25%) plus an additional 10% spread over the other three, or something more benign. Better top (so not busybox's) or htop versions also can show the load per CPU which is helpful to pinpoint hotspots...
> 
> If I run iperf3 with 10 parallel sessions then htop shows this (in the CAKE upstream direction I believe):
> 
>  1  [*                                                                                  0.7%]   Tasks: 19, 0 thr; 2 running
>  2  [*********************************************************************************100.0%]   Load average: 0.48 0.16 0.05
>  3  [#***************************************                                          44.4%]   Uptime: 10 days, 04:46:37
>  4  [************************************************                                  54.2%]
>  Mem[|#*                                                                         36.7M/3.84G]
>  Swp[                                                                                  0K/0K]
> 
> The other direction (-R), typically this:
> 
> 1  [#***********                                                                      13.0%]   Tasks: 19, 0 thr; 2 running
> 2  [***********************************************                                   53.9%]   Load average: 0.54 0.25 0.09
> 3  [#*************************************************                                55.8%]   Uptime: 10 days, 04:47:36
> 4  [**************************************************************************        84.4%]
> 
> Topology is:
> 
> PC - HGW -> Internet
> 
> iperf3 is run on the PC, HGW has CAKE in the -> Internet direction.
> 
>> Best Regards
>> 	Sebastian
>> 
>>> 
>>> root at OpenWrt:~# tc -s qdisc
>>> qdisc noqueue 0: dev lo root refcnt 2
>>> Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
>>> backlog 0b 0p requeues 0
>>> qdisc cake 8034: dev eth0 root refcnt 9 bandwidth 900Mbit diffserv3 triple-isolate nonat nowash no-ack-filter split-gso rtt 100.0ms raw overhead 0
>>> Sent 1111772001 bytes 959703 pkt (dropped 134, overlimits 221223 requeues 179)
>>> backlog 0b 0p requeues 179
>>> memory used: 2751976b of 15140Kb
>>> capacity estimate: 900Mbit
>>> min/max network layer size:           42 /    1514
>>> min/max overhead-adjusted size:       42 /    1514
>>> average network hdr offset:           14
>>> 
>>>                  Bulk  Best Effort        Voice
>>> thresh      56250Kbit      900Mbit      225Mbit
>>> target          5.0ms        5.0ms        5.0ms
>>> interval      100.0ms      100.0ms      100.0ms
>>> pk_delay          0us         22us        232us
>>> av_delay          0us          6us          7us
>>> sp_delay          0us          4us          5us
>>> backlog            0b           0b           0b
>>> pkts                0       959747           90
>>> bytes               0   1111935437        39440
>>> way_inds            0        22964            0
>>> way_miss            0          275            2
>>> way_cols            0            0            0
>>> drops               0          134            0
>>> marks               0            0            0
>>> ack_drop            0            0            0
>>> sp_flows            0            3            1
>>> bk_flows            0            1            0
>>> un_flows            0            0            0
>>> max_len             0        68130         3714
>>> quantum          1514         1514         1514
>>> 
>>> 
>>> --
>>> Mikael Abrahamsson    email: swmike at swm.pp.se_______________________________________________
>>> Bloat mailing list
>>> Bloat at lists.bufferbloat.net
>>> https://lists.bufferbloat.net/listinfo/bloat
>> 
> 
> -- 
> Mikael Abrahamsson    email: swmike at swm.pp.se