[Cake] 5ms target hurting tcp throughput tweakable?

[Andy Furniss]

Hi, I am new to cake and just messing around currently.

I notice that on my setup with vdsl2 20mbit sync the default 5ms target
on best effort hurts netperf throughput a bit as latency to host rises.

My setup.

tc qdisc add dev ppp0 handle 1:0 root cake bandwidth 19690kbit raw 
overhead 34 diffserv4

Where ppp0 is pppoe.

qdisc cake 1: root refcnt 2 bandwidth 19690Kbit diffserv4 triple-isolate 
rtt 100.0ms noatm overhead 56 via-ethernet
  Sent 3250414679 bytes 5976629 pkt (dropped 3404, overlimits 3402556 
requeues 0)
  backlog 0b 0p requeues 0
  memory used: 221952b of 4Mb
  capacity estimate: 19690Kbit
                  Bulk   Best Effort      Video       Voice
   thresh      1230Kbit   19690Kbit    9845Kbit    4922Kbit
   target        14.8ms       5.0ms       5.0ms       5.0ms
   interval     109.8ms     100.0ms     100.0ms     100.0ms
   pk_delay        63us         9us         0us       146us
   av_delay         7us         6us         0us        10us
   sp_delay         4us         4us         0us         4us
   pkts         1237775     4725460           0       16798
   bytes     1781536029  1472719560           0     1224478
   way_inds          11       43327           0           1
   way_miss       14051       69600           0        3066
   way_cols           0           0           0           0
   drops             81        3323           0           0
   marks              0           0           0           0
   sp_flows          36           1           0           0
   bk_flows           1           0           0           0
   un_flows           0           0           0           0
   max_len         1500        1500           0        1428

Testing to flent-eu.bufferbloat.net which is 50ms from me, putting
a single netperf upload into bulk gets up to 0.6 - 1mbit better throughput
that if it goes through best effort.

Trying a simulation on lan with netem and cake vs hfsc 100p fifo also
shows that latency doesn't need to rise much to start hurting netperf
throughput.

Is there any way or plans to allow users to relax slightly the target?