netdev - Re: Possible regression in HTB

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Message-ID: <48EDE26B.6040101@cdi.cz>
Date:	Thu, 09 Oct 2008 12:52:27 +0200
From:	Martin Devera <devik@....cz>
To:	Jarek Poplawski <jarkao2@...il.com>
CC:	Simon Horman <horms@...ge.net.au>,
	Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org,
	David Miller <davem@...emloft.net>
Subject: Re: Possible regression in HTB

Jarek Poplawski wrote:
> On Thu, Oct 09, 2008 at 08:22:49AM +0200, Martin Devera wrote:
>>>> Simon, can you try to these things (separately):
>>>> a/ increase quantum to the first class (say 10x)
>>> Hi Martin,
>>>
>>> Do you mean increase r2q ? If so, here are some results
>> no, no, add rather ... "quantum 50000" to the first class only
>> r2q affects computation for all classes
> 
> Yes, it's a half-documented parameter: not in the man, but e.g. here:
> tc class add htb help
> 
> BTW, I wonder if better priority/quantum doesn't actually harm here.
> When HTB lends the rate the first class here is always served at the
> beginning. And if it's over the hardware limit, this class's packets
> are waiting. Other classes get their chunks later, probably after the
> card did some cleaning, so they may never have to wait at this
> situation. So, maybe it would be interesting to try this other way:
> lower priority of the first class with a prio param e.g. 1?

It starts to seem too complex to me (too many races related hypotheses).
The original intent was to investigate possibly corrupted drr pointer,
but just now I think the only way is to stuff enough debug code into
htb and try myself...
It will be probable faster - once I find time to do it.
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