[Cake] Stranger target behaviour

[Dave Taht]

The second one is from the interval >> 4, which equates to 6.2ms. I
note I picked that because some early data (2012) we had showed that
target slightly greater than cable media acquision (6ms) time was a
slight win, and it did not hurt to use a number more evenly divisible
in binary than the arbitrary 5%.

Also there was somewhere else in the original code where I'd stopped
using the target variable entirely and just used the shifted interval,
but given low rates where we have to account for the MTU, that
approach does not work. (otherwise anytime I can replace a memory
access with a mere shift, I'd do it)

As for the first 5ms sample below, I am really behind on keeping up
with the code. After next weekend I would hope to have time, but I do
hope someone can step through all the permutations upon which init and
change can be called to nail it.

Somewhere on these threads someone suggested moving the target
calculation into userspace, which does not work well, IMHO, when cake
is the default qdisc, and we somehow get a means to actually get the
actual line rate.
Dave Täht
I just invested five years of my life to making wifi better. And,
now... the FCC wants to make my work, illegal for people to install.
https://www.gofundme.com/savewifi


On Sat, Oct 31, 2015 at 3:35 PM, Kevin Darbyshire-Bryant
<kevin at darbyshire-bryant.me.uk> wrote:
> Playing with latest JM authed commits on sch-cake & tc-adv.  Look at the
> target values:
>
> root at Router:~# tc -s qdisc change dev ifb4eth0 root cake internet
> root at Router:~# tc -s qdisc show dev ifb4eth0
> qdisc cake 8008: root refcnt 2 bandwidth 39300Kbit diffserv4 flows rtt
> 100.0ms noatm overhead 12
>  Sent 285837 bytes 1240 pkt (dropped 0, overlimits 144 requeues 0)
>  backlog 0b 0p requeues 0
> capacity estimate: 10511Kbit
>              Tin 0       Tin 1       Tin 2       Tin 3
>   thresh   39300Kbit   36843Kbit   29475Kbit    9825Kbit
>   target       5.0ms       5.0ms       5.0ms       5.0ms
> interval     100.0ms     100.0ms     100.0ms     100.0ms
> Pk-delay         0us        22us         0us         0us
> Av-delay         0us         6us         0us         0us
> Sp-delay         0us         2us         0us         0us
>   pkts             0        1240           0           0
>   bytes            0      285837           0           0
> way-inds           0           0           0           0
> way-miss           0         125           0           0
> way-cols           0           0           0           0
>   drops            0           0           0           0
>   marks            0           0           0           0
> Sp-flows           0           0           0           0
> Bk-flows           0           2           0           0
> last-len           0          82           0           0
> max-len            0        1514           0           0
>
> root at Router:~# tc -s qdisc change dev ifb4eth0 root cake rtt 100ms
> root at Router:~# tc -s qdisc show dev ifb4eth0
> qdisc cake 8008: root refcnt 2 bandwidth 39300Kbit diffserv4 flows rtt
> 100.0ms noatm overhead 12
>  Sent 757689 bytes 2374 pkt (dropped 0, overlimits 464 requeues 0)
>  backlog 0b 0p requeues 0
> capacity estimate: 5964Kbit
>              Tin 0       Tin 1       Tin 2       Tin 3
>   thresh   39300Kbit   36843Kbit   29475Kbit    9825Kbit
>   target       6.2ms       6.2ms       6.2ms       6.2ms
> interval     100.0ms     100.0ms     100.0ms     100.0ms
> Pk-delay         0us       286us         0us         0us
> Av-delay         0us        70us         0us         0us
> Sp-delay         0us         2us         0us         0us
>   pkts             0        2374           0           0
>   bytes            0      757689           0           0
> way-inds           0           0           0           0
> way-miss           0         157           0           0
> way-cols           0           0           0           0
>   drops            0           0           0           0
>   marks            0           0           0           0
> Sp-flows           0           0           0           0
> Bk-flows           0           2           0           0
> last-len           0          82           0           0
> max-len            0        1514           0           0
>
> Colour me confused :-)
>
> Kevin
>
>
> _______________________________________________
> Cake mailing list
> Cake at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/cake
>