[Cerowrt-devel] [Bloat] Comcast upped service levels -> WNDR3800 can't cope...

Jonathan Morton chromatix99 at gmail.com
Wed Sep 3 07:08:02 EDT 2014

On 3 Sep, 2014, at 9:15 am, Aaron Wood wrote:

> What this makes me realize is that I should go instrument the cpu stats with each of the various operating modes:
> * no shaping, anywhere
> * egress shaping
> * egress and ingress shaping at various limited levels:
>     * 10Mbps
>     * 20Mbps
>     * 50Mbps
>     * 100Mbps
> So I set this up tonight, and have a big pile of data to go through.  But the headline finding is that the WNDR3800 can't do more than 200Mbps ingress, with shaping turned off.  The GbE switch fabric and my setup were just fine (pushed some very nice numbers through those interfaces when on the switch), but going through the routing engine (NATing), and 200Mbps is about all it could do.
> I took tcp captures of it shaping past it's limit (configured for 150/12), with then rrul, tcp_download, tcp_upload tests.
> And I took a series of tests walking down from 100/12, 90/12, 80/12, ... down to 40/12, while capturing /proc/stats and /proc/softirqs once a second (roughly), so that can be processed to pull out where the load might be (initial peeking hints that it's all time spent in softirq).
>  If anyone wants the raw data, let me know, I'll upload it somewhere.  The rrul pcap is large, the rest of it can be e-mailed easily.

Given that the CPU load is confirmed as high, the pcap probably isn't as useful.  The rest would be interesting to look at.

Are you able to test with smaller packet sizes?  That might help to isolate packet-throughput (ie. connection tracking) versus byte-throughput problems.

 - Jonathan Morton

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