[Cake] Trouble with CAKE

[Thibaut]

> On 14 Dec 2019, at 10:50, Jonathan Morton <chromatix99 at gmail.com> wrote:
> 
>> On 14 Dec, 2019, at 1:52 am, Thibaut <hacks at slashdirt.org> wrote:
>> 
>> Culprit turned out to be easy to identify: it’s the current master HEAD.
>> 
>> Reverting 183b320 fixed the issue.
> 
> That's extremely odd.  That commit should only affect traffic carrying the LE DSCP, which is not the default.
> 
> Perhaps it was not actually the code change, but triggering a rebuild of the module?

No. I tried with and without multiple times: I built, installed, manually unloaded the module, made sure it was unloaded, loaded the new build; just to make sure as I noticed the module doesn’t print anything in dmesg when it’s loaded (feature request: print the current build version when loading, that would be most helpful in these circumstances).

There is absolutely no doubt that on my router, with this commit CAKE is broken, without it isn’t.

Here’s tc -s output with the broken version:

tc -s qdisc show dev wan
qdisc cake 800f: root refcnt 2 bandwidth 1200Kbit diffserv3 dual-srchost nat nowash ack-filter split-gso rtt 100.0ms atm overhead 48 no-sce 
 Sent 7711782 bytes 5454 pkt (dropped 144, overlimits 15493 requeues 0) 
 backlog 1616b 2p requeues 0
 memory used: 140864b of 4Mb
 capacity estimate: 1200Kbit
 min/max network layer size:           40 /    1500
 min/max overhead-adjusted size:      106 /    1749
 average network hdr offset:           14

                   Bulk  Best Effort        Voice
  thresh         75Kbit     1200Kbit      300Kbit
  target        242.2ms       15.1ms       60.6ms
  interval      484.5ms      110.1ms      155.6ms
  pk_delay          0us       60.0ms       26.8ms
  av_delay          0us       36.7ms        2.0ms
  sp_delay          0us       17.8ms        1.7ms
  backlog            0b        1514b         102b
  pkts                0         5467          133
  bytes               0      7913444        17970
  way_inds            0            0            0
  way_miss            0           44            2
  way_cols            0            0            0
  sce                 0            0            0
  marks               0            0            0
  drops               0          144            0
  ack_drop            0            0            0
  sp_flows            0            0            1
  bk_flows            0            1            0
  un_flows            0            0            0
  max_len             0         3028         1118
  quantum           300          300          300

qdisc ingress ffff: parent ffff:fff1 ---------------- 
 Sent 218759 bytes 3710 pkt (dropped 0, overlimits 0 requeues 0) 
 backlog 0b 0p requeues 0

Here’s the same output with the unbroken version:

tc -s qdisc show dev wan
qdisc cake 8011: root refcnt 2 bandwidth 1200Kbit diffserv3 dual-srchost nat nowash ack-filter split-gso rtt 100.0ms atm overhead 48 no-sce 
 Sent 3342962 bytes 2328 pkt (dropped 110, overlimits 6422 requeues 0) 
 backlog 4542b 3p requeues 0
 memory used: 83328b of 4Mb
 capacity estimate: 1200Kbit
 min/max network layer size:           40 /    1500
 min/max overhead-adjusted size:      106 /    1749
 average network hdr offset:           14

                   Bulk  Best Effort        Voice
  thresh         75Kbit     1200Kbit      300Kbit
  target        242.2ms       15.1ms       60.6ms
  interval      484.5ms      110.1ms      155.6ms
  pk_delay          0us       56.8ms        9.9ms
  av_delay          0us       36.7ms        854us
  sp_delay          0us        9.4ms        680us
  backlog            0b        4542b           0b
  pkts                0         2403           38
  bytes               0      3509764         4280
  way_inds            0            0            0
  way_miss            0           17            1
  way_cols            0            0            0
  sce                 0            0            0
  marks               0            0            0
  drops               0          110            0
  ack_drop            0            0            0
  sp_flows            0            0            1
  bk_flows            0            1            0
  un_flows            0            0            0
  max_len             0         1514          294
  quantum           300          300          300

qdisc ingress ffff: parent ffff:fff1 ---------------- 
 Sent 106781 bytes 1896 pkt (dropped 0, overlimits 0 requeues 0) 
 backlog 0b 0p requeues 0


HTH
Thibaut