[Cerowrt-devel] an option for a new platform?

David P. Reed dpreed at reed.com
Sat Dec 13 18:02:25 EST 2014

Anyone measured what is the actual bottleneck in 300 mb/s shaping?  On an Intel platform you can measure a running piece of code pretty accurately. I ask because it is not obvious a cpu needs to touch much of a frame to do shaping, so it seems more likely that the driver and memory management structures are the bottleneck.

But it is really easy to write very slow code in a machine with limited cache. So maybe that is it. 

On a multi core intel arch machine these days it is a surprising fact that a single core can't use up more than about 25 percent of  a socket's memory cycles so to get full i/o speed you need to be running your code on 4 cores or more... this kind of thing can really limit achievable speed of a poorly threaded design.  Architectural optimization needs more than llvm and clean code. You need to think about the whole software pipeline. Debian may not be great out of the box for this reason - it was never designed for routing throughput.

On Dec 12, 2014, Dave Taht <dave.taht at gmail.com> wrote:
>There was a review of that hardware that showed it couldn't push more
>than 600Mbit natively (without shaping). I felt that the ethernet
>driver could be improved significantly after looking it over, but
>didn't care for the 600mbit as a starting point to have to improve
>Not ruling it out, though! It met quite a few requirements we have.
>On Thu, Dec 11, 2014 at 11:33 PM, Erkki Lintunen <ebirdie at iki.fi>
>> Hello,
>> while enjoying and reading another thread from the list...
>>> -------- Forwarded Message --------
>>> Subject: Re: [Cerowrt-devel] how is everyone's uptime?
>>> Date: Thu, 11 Dec 2014 16:42:37 -0800
>>> From: Dave Taht <dave.taht at gmail.com>
>> [snip]
>>> But frankly, I would prefer for most of the chaos there to subside
>and to find
>>> a new, additional platform, to be working on before resuming work,
>>> that can do inbound shaping at up to 300mbit. And
>>> to be more openwrt compatible in whatever we do, whatever that is.
>> this reminded me that another day I passed a web-page of a platform
>> in the hope this has not been on the list yet passing it forward.
>> <http://www.pcengines.ch/apu.htm>
>> An interesting tidbit in the platform is the choice of firmware, I
>> think. Haven't seen any board yet with the similar choice by the
>> manufacturer. With a quick summing from the vendor part catalog, the
>> platform is sub 200 EUR (238 USD in current exchange rate) for an
>> working assembly of 3x 1GbE, 4G ram, 1G flash, 802.11a/b/g/n radio...
>> I can't say anything how capable the hw might be for the stated
>> shaping performance. I have had an ALIX board from their previous
>> generation for years and its been humming nicely though I haven't
>> it to its envelope.
>> Best
>> Erkki
>> _______________________________________________
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>Dave Täht
>Cerowrt-devel mailing list
>Cerowrt-devel at lists.bufferbloat.net

-- Sent from my Android device with K-@ Mail. Please excuse my brevity.
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