netdev - Re: Possible regression in HTB

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Message-ID: <20081008065551.GB4174@ff.dom.local>
Date:	Wed, 8 Oct 2008 06:55:51 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	Simon Horman <horms@...ge.net.au>, netdev@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	Martin Devera <devik@....cz>
Subject: Re: Possible regression in HTB

On Wed, Oct 08, 2008 at 02:31:26AM +0200, Patrick McHardy wrote:
...
> I'm pretty sure that the differences are caused by HTB not being
> in control of the queue since the device is the real bottleneck
> in this configuration.

Yes, otherwise there would be no requeuing. And, btw. the golden rule
of scheduling/shaping is limiting below "hardware" limits.

> Its quite possible that there simply might
> a subtle timing change that causes feedback through HTBs borrowing
> and ceiling.

I'd add my previous suspicion there could be not enough enqeuing on
time for the fastest class (could be also very bursty), so other
classes can borrow more.

>
> So what would really be useful to understand this is to make HTB
> control the queue and see if it behaves as expected.
>

Right, trying with lower rates/ceils should explain this.

Jarek P.
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