netdev - Re: htb parallelism on multi-core platforms

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Date:	Thu, 23 Apr 2009 22:19:45 +0200 (CEST)
From:	Jesper Dangaard Brouer <hawk@...u.dk>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	Radu Rendec <radu.rendec@...s.ro>,
	Denys Fedoryschenko <denys@...p.net.lb>, netdev@...r.kernel.org
Subject: Re: htb parallelism on multi-core platforms

On Thu, 23 Apr 2009, Jarek Poplawski wrote:

> On Thu, Apr 23, 2009 at 04:56:42PM +0300, Radu Rendec wrote:
>> On Thu, 2009-04-23 at 08:20 +0000, Jarek Poplawski wrote:
>>
>> I am aware of the thread and even tried out the author's patch (despite
>> the fact that David Miller suggested it was not sane). Under heavy
>> (simulated) traffic nothing was changed: only one ksoftirqd using 100%
>> CPU, one CPU in 100%, others idle. This only confirms what I've already
>> been told: htb is single threaded by design.

Its more general that just HTB.  We have general Qdisc serialization 
point in net/sched/sch_generic.c by the qdisc_lock(q).

>> It also proves that most of the packet processing work is actually in 
>> htb.

I'm not sure that statement is true.
Can you run Oprofile on the system?  That will tell us exactly where time 
is spend...

> ...
> I thought about using some trick with virtual devs instead, but maybe
> I'm totally wrong.

I like the idea with virtual devices, as each virtual device could be 
bound to a hardware tx-queue.

Then you just have to construct your HTB trees on each virtual 
device, and assign customers accordingly.

I just realized, you don't use a multi-queue capably NIC right?
Then it would be difficult to use the hardware tx-queue idea.
Have you though of using several physical NICs?

Hilsen
   Jesper Brouer

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