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

Jonathan Morton chromatix99 at gmail.com
Sun Aug 31 06:18:46 EDT 2014

On 31 Aug, 2014, at 1:30 am, Dave Taht wrote:

> Could I get you to also try HFSC?

Once I got a kernel running that included it, and figured out how to make it do what I wanted...

...it seems to be indistinguishable from HTB and FQ in terms of CPU load.

Actually, I think most of the CPU load is due to overheads in the userspace-kernel interface and the device driver, rather than the qdiscs themselves.  Something about TBF causes more overhead - it goes through periods of lower CPU use similar to the other shapers, but then spends periods at considerably higher CPU load, all without changing the overall throughput.

The flip side of this is that TBF might be producing a smoother stream of packets.  The receiving computer (which is fast enough to notice such things) reports a substantially larger number of recv() calls are required to take in the data from TBF than from anything else - averaging about 4.4KB rather than 9KB or so.  But at these data rates, it probably matters little.

FWIW, apparently Apple's variant of the GEM chipset doesn't support jumbo frames.  This does, however, mean that I'm definitely working with an MTU of 1500, similar to what would be sent over the Internet.

These tests were all run using nttpc.  I wanted to finally try out RRUL, but the wrappers fail to install via pip on my Gentoo boxes.  I'll need to investigate further before I can make pretty graphs like everyone else.

 - Jonathan Morton

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