netdev - Re: Not understand some in htb_do

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Date:	Wed, 16 Jan 2008 06:15:34 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Martin Devera <devik@....cz>
CC:	Badalian Vyacheslav <slavon@...telecom.ru>, netdev@...r.kernel.org
Subject: Re: Not understand some in htb_do_events function

Martin Devera wrote:
>>
>> So this was meant to protect against endless loops?
>>
>>> 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 ?
>>
>>
>> Unfortunately not, but I believe simply removing the limit
>> completely would be better than picking an arbitary value.
> 
> Grrr my comp crashed while I was writing this mail. Well the second
> attempt.
> When we allow unlimited events per dequeue, then there is case where
> all N classes in qdisc can be in the event queue with the same target
> time. Then they will all be acted on in the loop within single dequeue,
> costing us say some milliseconds. Additionaly, it tends to repeat itself
> then in cycles.

I see.

> Maybe it is acceptable but it seemed to me as rather big latency.
> Thus I wanted to do only limited work per dequeue call. One possibility
> is to remove the limit and "see what happend in wild".
> 
> What do u think about to do limited no of transitions and then schedule
> tasklet to do the rest (again in limited buckets) ?


Alternatively we could just remove the printk and do what you
suggested first, return q->now + 1 to immediately continue
processing, but send out a packet first.
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