netdev - Re: HTB accuracy for high speed

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Message-ID: <4A1519CC.9030002@cosmosbay.com>
Date:	Thu, 21 May 2009 11:07:24 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Jarek Poplawski <jarkao2@...il.com>
CC:	Vladimir Ivashchenko <hazard@...ncoudi.com>,
	netdev@...r.kernel.org, kaber@...sh.net, davem@...emloft.net,
	devik@....cz, Antonio Almeida <vexwek@...il.com>,
	Corey Hickey <bugfood-ml@...ooh.org>
Subject: Re: HTB accuracy for high speed

Jarek Poplawski a écrit :
> On Thu, May 21, 2009 at 10:44:00AM +0300, Vladimir Ivashchenko wrote:
>>> I don't know why more of esfq wasn't merged, anyway similar
>>> functionality could be achieved in current kernels with sch_drr +
>>> cls_flow, alas not enough documented. Here is some hint:
>>> http://markmail.org/message/h24627xkrxyqxn4k
>> Can I balance only by destination IP using this approach? 
>> Normal IP flow-based balancing is not good for me, I need 
>> to ensure equality between destination hosts.
> 
> Yes, you need to use flow "dst" key, I guess. (tc filter add flow help)
> 
> Jarek P.
> 
>>> PS: I guess, you wasn't very consistent if your main problem was
>>> exceeding or not reaching htb rate, and there is quite a difference.
>> Yes indeed :(
> 
> Generally, the most common reasons are:
> - too short (or zero) tx queue length or/plus some disturbances in
>   maintaining the flow - for not reaching the rate


> - gso/tso or other non standard packets sizes - for exceeding the
>   rate.

Could we detect this at runtime and emit a warning (once) ?

Or should we assume guys using this stuff should be smart enough ?
I confess I made this error once and this was not so easy to spot...
	

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