[LARTC] HFSC parameter

[Patrick McHardy]

Thossapron Apinyapanha wrote:
> tc command's HFSC have a lot parameter with 4 curve type
> 
> SC curve -> umax dmax rate
> LS curve -> umax dmax rate
> RT curve -> umax dmax rate
> UL curve -> umax dmax rate
> 
> so i'dont know which parameter are appropriate for my test case
> such real time class which curve are appropriate and good working result.

LS = link-share service curve, defines relation of service between
sibling classes. Can be used for intermediate and leaf classes.

UL = upper-limit service curve, limits LS curve.

RS = real-time service curve, defines absolute service guarantees
for leaf classes. Can be used, but does nothing for intermediate
classes.

SC = service curve, sets LS and RS to the same curve. Should usually
be used for leaf-classes instead of RS.

> my assumption about umax,dmax,rate ... this is true
> first, HFSC will doing with "umax" rate but after delay exceed "dmax" rate,
> HFSC will change rate to "rate" ????

No, this is true for m1, d and m2 (use rate m1 for time d, then m2).
umax, dmax and rate are another way to specify the curve, m2 == rate
and m1 and d are calculated from umax and dmax.