netdev - Re: CBQ broken in 2.6

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Message-Id: <1264595308.29501.30.camel@tranquility.sigsegv.cx>
Date:	Wed, 27 Jan 2010 12:28:28 +0000
From:	Anton Ivanov <anton.ivanov@...-begemot.co.uk>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: CBQ broken in 2.6

Thanks it is indeed sch_cbq.c,

I have been going through the code in the meantime and found a place
where cl->tparent can be modified further down in the routine in
question. There is an invocation of cbq_set_lss() around the end of
cbq_change_class() which can do that.

I am rebuilding the kernel for my CBQ box with a few printks at the
moment to see if it modified there or not.

In any case here is the tell-tale symptom:

class cbq 1:16 parent 1: leaf 76: rate 5600Kbit (bounded,isolated) prio
2
 Sent 162051 bytes 925 pkt (dropped 0, overlimits 0 requeues 0)
 rate 0bit 0pps backlog 0b 0p requeues 0
  borrowed 201 overactions 0 avgidle 78 undertime 0

That is a bounded class. Its borrowed should be always 0 no matter what.
That is basically a broken CBQ implementation.

An elementary network test suite shows the same result - it is being
allowed to borrow.

I am happy to send the whole config if necessary if someone wants to
look at it.

Brgds,

[snip]

-- 
   Understanding is a three-edged sword:
            your side, their side, and the truth. --Kosh Naranek

A. R. Ivanov
E-mail:  anton.ivanov@...-begemot.co.uk
WWW:     http://www.kot-begemot.co.uk/

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