netdev - Re: thousands of classes, e1000 TX unit hang

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Date:	Tue, 5 Aug 2008 14:13:58 +0300
From:	Denys Fedoryshchenko <denys@...p.net.lb>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: thousands of classes, e1000 TX unit hang

On Tuesday 05 August 2008, Jarek Poplawski wrote:
> On 05-08-2008 12:05, Denys Fedoryshchenko wrote:
> > I found, that packetloss happening when i am deleting/adding classes.
> > I attach result of oprofile as file.
>
> ...
>
> Deleting of estimators (gen_kill_estimator) isn't optimized for
> a large number of them, and it's a known issue. Adding of classes
> shouldn't be such a problem, but maybe you could try to do this
> before adding filters directing to those classes.
>
> Since you can control rate with htb, I'm not sure you really need
> policing: at least you could try if removing this changes anything.
> And I'm not sure: do these tx hangs happen only when classes are
> added/deleted or otherwise too?
>
> Jarek P.

Policer is creating burst for me.
For example first 2Mbyte(+rate*time if need more precision) will pass on high 
speed (1Mbit), then if flow is still using maximum bandwidth will be 
throttled to rate of HTB. When i tried to play with cburst/burst values in 
HTB i was not able to archieve same results. I can do same with TBF and his 
peakrate/burst, but not with HTB.

It happens when root qdisc deleted(which holds around 130 child classes). 
Probably gen_kill_estimator taking all resources while i am deleting root 
class.
I did some test, on machine with 150 ppp interfaces (Pentium 4 3.2 Ghz),
just by deleting root qdisc and i got huge packetloss. When i am just adding 
classes - there is no significant packetloss.
Probably it is not right thing, when i am deleting qdisc on ppp - causing 
packetloss on whole system? Is it possible to workaround, till 
gen_kill_estimator will be rewritten?

But sure i can try to avoid "mass deleting" classes, but i think many people 
will hit this bug, especially newbies, who implement "many class" setup.

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