[Bloat] CAKE in openwrt high CPU

[Mikael Abrahamsson]

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