netdev - Re: HTB - What's the minimal value for 'rate' parameter?

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Date:	Fri, 9 Apr 2010 16:40:44 +0100
From:	Antonio Almeida <vexwek@...il.com>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	netdev@...r.kernel.org, kaber@...sh.net, davem@...emloft.net,
	devik@....cz
Subject: Re: HTB - What's the minimal value for 'rate' parameter?

So, what about the rate limit miss?
As you can see the ceil of class 1:2 is set to 4096Kbit but its
sending rate is actually 8071Kbit!
It looks like classes 1:10 and 1:11 are ignoring hierarchical rate
restrictions of class 1:2
Here:
class htb 1:2 parent 1:1 rate 4096Kbit ceil 4096Kbit burst 3655b cburst 3655b
 Sent 84285894 bytes 55671 pkt (dropped 0, overlimits 0 requeues 0)
 rate 8071Kbit 666pps backlog 0b 0p requeues 0
 lended: 0 borrowed: 0 giants: 0
 tokens: -937499999 ctokens: -937499999




On Thu, Apr 8, 2010 at 10:33 PM, Jarek Poplawski <jarkao2@...il.com> wrote:
> Antonio Almeida wrote, On 04/08/2010 01:07 PM:
>
>> Hi!
>
> Hi!
>
>> I've been using HTB for a while, and we've already sent some e-mails
>> each other when resolving HTB accuracy issue.
>> When using HTB, I realised that for some configurations the rate limit
>> doesn't work.
>> I suspect that the problem is the minimum value of rate parameter,
>> which I cant figure out what is.
>>
>> I simple configuration that turns out to be wrong is as fallows: The
>> root (1:1) gets the link bandwidth configuration; the second (1:2) is
>> set to 4096Kbit; then I have two branches (1:10 and 1:11) with rate
>> 1024Kbit and ceil 4096Kbit; and finally a leaf class in each branch
>> (1:111 below 1:11, and 1:101 below 1:10) with rate 8bit and ceil
>> 4096Kbit, and the same priority.
>> I don't want to have sustained rate, and since I must configure 'rate'
>> parameter I decide to set it to 8bits - which is the minimal accepted
>> value. My cue goes for 'rate' parameter. If I set 'rate' parameter to
>> 1Kbit for instance, the problem disappears and the shaping is done
>> perfectly.
>>
>> So, I'm looking for help to find out if the problem is actually in
>> this parameter configuration or if it's just coincidence and I'll get
>> the same problem ahead :(
>> What's the minimal value for 'rate' parameter using HTB qdisc?
>
>
> I think "reasonable" or "minimally useful" (for common use) should be
> enough, and 8bits meaning one 1500 byte packet per 25 minutes or
> something, doesn't look like this to me.
>
> This changelog:
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=a4a710c4a7490587406462bf1d54504b7783d7d7
> mentions ~2 minutes as max time for accounting, so 1 max packet
> per 2 minutes should give such a minimal rate, I guess, but I'd
> still multiply it a few times to call it useful.
>
> Regards,
> Jarek P.
>
>
>
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