netdev - Re[2]: htb parallelism on multi-core platforms

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Date:	Thu, 30 Apr 2009 17:04:26 +0300
From:	Calin Velea <calin.velea@...enii.ro>
To:	Radu Rendec <radu.rendec@...s.ro>
CC:	Calin Velea <vcalinus@...enii.ro>,
	Jarek Poplawski <jarkao2@...il.com>,
	Jesper Dangaard Brouer <hawk@...u.dk>,
	Denys Fedoryschenko <denys@...p.net.lb>,
	netdev <netdev@...r.kernel.org>
Subject: Re[2]: htb parallelism on multi-core platforms


Thursday, April 30, 2009, 2:19:36 PM, you wrote:

> On Thu, 2009-04-30 at 01:49 +0300, Calin Velea wrote:
>>    I tested with e1000 only, on a single quad-core CPU - the L2 cache was
>> shared between the cores.
>> 
>>   For 8 cores I suppose you have 2 quad-core CPUs. If the cores actually
>> used belong to different physical CPUs, L2 cache sharing does not occur -
>> maybe this could explain the performance drop in your case.
>>   Or there may be other explanation...

> It is correct, I have 2 quad-core CPUs. If adjacent kernel-identified
> CPUs are on the same physical CPU (e.g. CPU0, CPU1, CPU2 and CPU3) - and
> it is very probable - then I think the L2 cache was actually shared.
> That's because the used CPUs where either 0-3 or 4-7 but never a mix of
> them. So perhaps there is another explanation (maybe driver/hardware).

>>   It could be the only way to get more power is to increase the number 
>> of devices where you are shaping. You could split the IP space into 4 groups
>> and direct the trafic to 4 IMQ devices with 4 iptables rules -
>> 
>> -d 0.0.0.0/2 -j IMQ --todev imq0,
>> -d 64.0.0.0/2 -j IMQ --todev imq1, etc...

> Yes, but what if let's say 10.0.0.0/24 and 70.0.0.0/24 need to share
> bandwidth? 10.a.b.c goes to imq0 qdisc, and 70.x.y.z goes to imq1 qdisc,
> and the two qdiscs (HTB sets) are independent. This will result in a
> maximum of double the allocated bandwidth (if HTB sets are identical and
> traffic is equally distributed).

>>   The performance gained through parallelism might be a lot higher than the 
>> added overhead of iptables and/or ipset nethash match. Anyway - this is more of
>> a "hack" than a clean solution :)
>>
>> p.s.: latest IMQ at http://www.linuximq.net/ is for 2.6.26 so you will need to try with that

> Yes, the performance gained through parallelism is expected to be higher
> than the loss of the additional overhead. That's why I asked for
> parallel HTB in the first place, but got very disappointed after David
> Miller's reply :)

> Thanks a lot for all the hints and for the imq link. Imq is very
> interesting regardless of whether it proves to be useful for this
> project of mine or not.

> Radu Rendec


   Indeed, you need to use ipset with nethash to avoid bandwidth doubling.
Let's say we have a shaping bridge: customer side (download) is
on eth0, the upstream side (upload) is on eth1.

   Create customer groups with ipset (http://ipset.netfilter.org/)

ipset -N cust_group1_ips nethash
ipset -A cust_group1_ips <subnet/mask>
....
....for each subnet



To shape the upload with multiple IMQs:

-m physdev --physdev-in eth0 -m set --set cust_group1_ips src -j IMQ --to-dev 0
-m physdev --physdev-in eth0 -m set --set cust_group2_ips src -j IMQ --to-dev 1
-m physdev --physdev-in eth0 -m set --set cust_group3_ips src -j IMQ --to-dev 2
-m physdev --physdev-in eth0 -m set --set cust_group4_ips src -j IMQ --to-dev 3


 You will apply the same htb upload limits to imq 0-3.
 Upload for customers having source IPs from the first group will be shaped
by imq0, for the second, by imq1, etc...


For download:

-m physdev --physdev-in eth1 -m set --set cust_group1_ips dst -j IMQ --to-dev 4
-m physdev --physdev-in eth1 -m set --set cust_group2_ips dst -j IMQ --to-dev 5
-m physdev --physdev-in eth1 -m set --set cust_group3_ips dst -j IMQ --to-dev 6
-m physdev --physdev-in eth1 -m set --set cust_group4_ips dst -j IMQ --to-dev 7

and apply the same download limits on imq 4-7


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-- 
Best regards,
 Calin                            mailto:calin.velea@...enii.ro

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