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

Jonathan Morton chromatix99 at gmail.com
Sat Aug 30 13:33:45 EDT 2014

On 30 Aug, 2014, at 4:03 pm, Toke Høiland-Jørgensen wrote:

> Jonathan Morton <chromatix99 at gmail.com> writes:
>> Looking at the code, HTB is considerably more complex than TBF in
>> Linux, and not all of the added complexity is due to being classful
>> (though a lot of it is). It seems that TBF has dire warnings all over
>> it about having limited packet-rate capacity which depends on the
>> value of HZ, while HTB has some sort of solution to that problem.
> Last I checked, those warnings were out-dated. Everything is in
> nanosecond resolution now, including TBF. I've been successfully using
> TBF in my experiments at bandwidths up to 100Mbps (on Intel Core2 x86
> boxes, that is).

Closer inspection of the kernel code does trace to the High Resolution Timers, which is good.  I wish they'd update the comments to go with that sort of thing.

I've managed to run some tests now, and my old PowerBook G4 can certainly handle either HTB or TBF in the region of 200Mbps, at least for simple tests over a LAN.  The ancient Sun GEM chipset (integrated into the PowerBook's northbridge, actually) doesn't seem willing to push more than about 470Mbps outbound, even without filtering - but that might be normal for a decidedly PCI/AGP-era machine.  I'll need to investigate more closely to see whether there's a CPU load difference between HTB and TBF in practice.

I have two other machines which are able to talk to each other at ~980Mbps.  They're both AMD based, and one of them is a "nettop" style MiniITX system, based around the E-450 APU.  The choice of NIC, and more specifically the way it is attached to the system, seems to matter most - these both use an RTL8111-family PCIe chipset.

 - Jonathan Morton

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