netdev - Re: What queues/buffers does tc-netem use?

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Date:	Thu, 16 Jul 2015 12:48:33 +0000
From:	"Motejlek, Petr" <pmotejle@...mai.com>
To:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Hagen Paul Pfeifer <hagen@...u.net>
CC:	"netem@...l.org" <netem@...l.org>
Subject: Re: What queues/buffers does tc-netem use?

Hello Hagen,

Could you please give me some example of such a tc command that would tell me the statistics? I am not sure what you mean.

Is there a way I can manipulate the internal rbtree queue size, please?

Thank you

Petr MOTEJLEK
________________________________________
From: Hagen Paul Pfeifer <hagen@...u.net>
Sent: Thursday, July 16, 2015 2:42 PM
To: netdev@...r.kernel.org; Motejlek, Petr
Cc: netem@...l.org
Subject: Re: What queues/buffers does tc-netem use?

> On July 16, 2015 at 1:28 PM "Motejlek, Petr" <pmotejle@...mai.com>
> wrote:

> I was wondering what queues/buffers does netem use and how does one
> control or monitor them?

netem uses his own rbtree based queue. You can use tc(1) to get
statistics.

> I could not find this information anywhere and I am not that good in
> reading the sources to be able to tell enough about this :) If we talk
> only about the situation where netem is the root qdisc for a particular
> interface, I would imagine it might be using the txqueue of that
> interface, but I am not sure if that's really the case...

Saddly there is no netem implementation documentation, but the source code
is straightforward. You may take a look:

http://lxr.free-electrons.com/source/net/sched/sch_netem.c

Cheers, Hagen
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