netdev - Re: Not understand some in htb_do

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Date:	Tue, 15 Jan 2008 16:51:00 +0300
From:	Badalian Vyacheslav <slavon@...telecom.ru>
To:	Martin Devera <devik@....cz>
CC:	netdev@...r.kernel.org, kaber@...sh.net
Subject: Re: Not understand some in htb_do_events function

Martin Devera пишет:
> Patrick McHardy wrote:
>> Badalian Vyacheslav wrote:
>>> Hello all.
>>> I have many messages like "htb: too many events !" in dmesg.
>>>
>>> Try to see code and find that function try do 500 events at call.
>>> Hm... may anyone ask why 500? Why its not dynamic value based on 
>>> performance of PC?
>>
>>
>> Thats a good question, I wonder why it is limited at all.
>> Martin, any hints?
>>
>>
>
> Hi, I recently replied someone to the same question:
>
> > it is possible when during one jiffie (1 or 10ms) more than 500 classes
> > changed its state. It is meant to protect your system from livelock.
> > The constant should be set to something like
> > bogomips/bogocomplexity_of_state_change but it was not done.
>
> the solution I have in my mind is to change
>    if (net_ratelimit())
>                  printk(KERN_WARNING "htb: too many events !\n");
>          return HZ/10;
>  to
>    return 1;
>
> to drain extra events asap. It the time of writing I was not able to
> come with better solution and there were more bugs related to this
> part of code than now.
> We want way to smooth big burst of events over more dequeue invocations
> in order to not slow dequeue too much. Constant 500 is max. allowed
> "slowdown" of dequeue.
> Any bright idea how to do it more elegant, Patrick ?
>
> brgds, devik

Hmm.. i simple see that if i get messages like this in dmesg my PC limit 
speed, but i have many free CPU and HTB classes have not full bandwidth 
load....
If i delete half rules - i get bandwidth that i wont. I wrong understand 
that if we have this limit (constant 500) my PC can't get full performance?

Look scheme (example in my memory... not real numbers... for idea only):
HTB (default 1)
- Class 1 (rate 250mbs cell 500 prio 1)
---- Here 8000 HTB rules (parent 1) (rate 1kbs, cell from 200kbs to 5mbs)
- Class 2 (rate 250mbs cell 500 prio 1)

I always go to 2.
try ttcp.
current rate in class 1 - above 150mbs
current rate in class 2 - above 200mbs
Load avg above 0.10 - 0.25
Idle - 80%
 
Try delete half rules
current rate in class 1 - above 100mbs
current rate in class 2 - above 400mbs
Load avg above 0.10 - 0.25
Idle - 80%

All traffic in class 2 do i witch ttcp! its not deleted clients from 
class 1.

Any idea? Thanks.
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