Re: [LARTC] ATTN Andreas Klauer: ASCII art + comments, please?

[gypsy <gypsy@iswest.com>]

Andreas Klauer wrote:
> 
> On Sun, Mar 05, 2006 at 02:33:17PM -0800, gypsy wrote:
> > Since I understand your ASCII art and comments, I would very much
> > appreciate it if you would draw what you see and criticize the
> > following.  Hopefully I'll better understand after that!
> 
> Uh, right. Don't take anything I say for granted, though.

Understood.

> > tc qdisc add dev imq0 root handle 1: htb default 20
> >
> > tc class add dev imq0 parent 1: classid 1:2 htb rate 4522kbit ceil \
> >    4760kbit burst 16k cburst 16k quantum 1500
> >
> > tc class add dev imq0 parent 1:2 classid 1:1 htb rate 4522kbit ceil \
> >    4760kbit burst 16k cburst 16k
> >
> > tc class add dev imq0 parent 1:1 classid 1:10 htb rate 2487kbit \
> >    ceil 4760kbit burst 16k cburst 16k quantum 1500 prio 1
> >
> > tc class add dev imq0 parent 1:1 classid 1:20 htb rate 2034kbit \
> >    ceil 4341kbit burst 10k cburst 16k quantum 1500 prio 4
> 
> First, here is what I see:
> 
> 1: HTB root qdisc (default 20)
> |
> \--- 1:2 HTB root class (4522kbit/4760kbit)
>      |
>      \--- 1:1 HTB class (4522kbit/4760kbit)
>           |
>           \--- 1:10 HTB leaf class (2487kbit/4760kbit)
>           \--- 1:20 HTB leaf class (2034kbit/4341kbit)
> 
> Now on to the criticising; the root class has a higher ceil than rate.
> However, different rate/ceil makes only sense if there is someone to
> borrow bandwidth from, which is not the case here. The root class
> acquires bandwidth directly from the QDisc, which has unlimited resources,
> as the root class itself is supposed to be the limiting factor. So what
> you have here should practically be no different from a 4760kbit class.
> 
> The 1:1 class seems to be useless; it has exactly the same settings
> as it's parent, except for quantum, which is not explicitely set.
> Furthermore, it does not have any siblings. Does not make sense to
> me as such a class will just use exactly the same rate as it's parent.
> Compare the statistics of these two classes below.
> 
> > class htb 1:1 parent 1:2 rate 4522Kbit ceil 4760Kbit burst 16Kb cburst
> > 16Kb
> >  Sent 7826237 bytes 27128 pkts (dropped 0, overlimits 0)
> >  rate 1728bit 4pps
> >  lended: 1954 borrowed: 0 giants: 0
> >  tokens: 39532 ctokens: 37555
> >
> > class htb 1:2 root rate 4522Kbit ceil 4760Kbit burst 16Kb cburst 16Kb
> >  Sent 7826237 bytes 27128 pkts (dropped 0, overlimits 0)
> >  rate 1728bit 4pps
> >  lended: 0 borrowed: 0 giants: 0
> >  tokens: 39532 ctokens: 37555
> 
> As for the leaf classes, their rates are fine (add up to the parent
> class rate), except that the parent actually can use 4760kbit rate
> rather than 4522kbit. Their priorities are questionable; using 1 and 4
> here should not be any different from 1 and 2 or 3 and 6 or 0 and 1.

The four is a "leftover", but I want it clear that 1:10 has priority
over 1:20.
 
> It's one high- and one low-priority class either way. I would probably
> set a priority just for the low priority class, so that it becomes
> more obvious what is intended by this setting here.
> 
> That what you wanted?
> 
> Regards
> Andreas Klauer

Thank you.  Yes, that is exactly what I wanted.  It was also every bit
as understandable as I expected, so THANK YOU again.

I thrashed with this because when I set it up with only a 1:1 (where 1:2
is now), NOTHING ever was recorded in the root and no borrowing would
occur.  The more I thrashed, the more confused I became.  With this, I
think I can fix it.
--
gypsy
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