netdev - Re: [PATCH] sch_htb.c consume the classes's tokens bellow the HTB_CAN

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Message-ID: <20091104104245.GB6224@ff.dom.local>
Date:	Wed, 4 Nov 2009 10:42:45 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	Jamal Hadi Salim <hadi@...erus.ca>, devik@....cz,
	netdev@...r.kernel.org
Subject: Re: [PATCH] sch_htb.c consume the classes's tokens bellow the
	HTB_CAN_SEND level

On Wed, Nov 04, 2009 at 05:16:42PM +0800, Changli Gao wrote:
...
> It is just correct. You focus on 1 second fairness, while I focus on 2
> seconds fairness.

The whole example was very simplified, so it all would certainly
differ in time and real sends, especially with an interaction of
more classes. But, generally, main HTB algorithm seems to be quite
well tested against various fair and unfair cases, starting from
the author's examples:
http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm
so, I guess, this type of a bug would really show somewhere long time
ago.

> The token bucket and ctoken bucket both use cl->mbuffer to control
> rate granularities. If we don't account token bucket when the
> corresponding class in HTB_MAY_BORROW mode, the cl->mbuffer will
> become useless.

cl->mbuffer is only to limit some extreme effects, so more of an
exception, not a main tool of rate control. (It really should be
useless most of the time if classes don't stop sending and aren't
deprived of their full rate for really long time.)

Regards,
Jarek P.
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