Re: [LARTC] Is ESFQ working?

From: Corey Hickey <bugfood-ml@fatooh.org>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] Is ESFQ working?
Date: Sun, 11 Feb 2007 19:10:34 +0000	[thread overview]
Message-ID: <45CF6A2A.3050009@fatooh.org> (raw)
In-Reply-To: <200702111301.51685.alejandro_aero@yahoo.es>

Alejandro Lorenzo Gallego wrote:
> On Sunday 11 February 2007 16:48:10 Tomasz Chilinski wrote:
>> On Sun, 11 Feb 2007 16:19:54 +0100, Alejandro Lorenzo Gallego wrote
>>
>>>>> [cut]
>>>> Have u tried to replace CLASSIFY target by MARK target and then using
>>>> fw filter? I have got bad experience with CLASSIFY target.
>>> Behaviour is identical if i use classify or mark, however, i
>>> expected this, because the packets do go to the right classes, it's
>>> just it looks that ESFQ is not assuring fairness between users
>> Which version of ESFQ? Patch for 2.6.15.1 or 2.6.19.2?
>>
>> Bests, Tomasz Chilinski.
>>
> 
> Actually for 2.6.29.2 

I assume that's a typo and you mean '2.6.19.2'.

> And i made some progress, using a depth parameter higher than default (800) it 
> behaves better and closer to fairness.... 

The default for depth is only 128. You're hashing by dst, right? On your
network, how many destinations will be receiving packets concurrently?
In other words, how many of your users will be downloading at the same time?

> ¿Can some explain the exact meaning of limit and depth options?

I am 95% sure of the following, which isn't in the ESFQ documentation
yet because I just recently read the relevant paperwork and tried to
understand more of the code.

'Limit' is the total number of packets ESFQ will queue before it starts
finding packets to drop.

ESFQ divides traffic into a number of smaller queues ("slots"), one for
each flow. Flows are distinguished based on whatever aspect of the
packets is hashed, such as source or destination. 'Depth' is the maximum
number of slots.

If there are more flows than 'depth', some flows might actually start
sharing slots. Obviously, this is not good, and fairness will suffer.

If there are 'limit' number of packets, ESFQ will simply drop a packet
from the slot that has the most packets. This doesn't hurt fairness,
since the longest slot will generally correspond to whichever flow has
tried to transfer the most packets recently.

-Corey
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