[Bloat] Best practices for paced TCP on Linux?

Steinar H. Gunderson sgunderson at bigfoot.com
Fri Apr 6 15:21:38 PDT 2012

On Fri, Apr 06, 2012 at 02:49:38PM -0700, Dave Taht wrote:
> It would be best to get some packet captures from user's streams that are
> complaining of the issue.

I'll try asking some users.

> Most 10Gige network cards have the ability to have multiple hardware queues
> that will do some FQ for you.
> SFQ or QFQ will FQ the output streams. SFQRED or QFQ + something will be
> able to do some level of queue management but not 'shaping', or 'packet pacing'
> However in your environment you will need the beefed up SFQ that is in 3.3.
> and BQL. If you are not saturating that 10GigE card, you can turn off TSO/GSO
> as well.

We're not anywhere near saturating our 10GigE card, and even if we did, we
could add at least one 10GigE card more.

> You can reduce your tcp sent windows.

Do you know how?

> I have a debloat script (with about 5 out of tree versions) that tries it's best
> to do the right thing on home gear and takes a bit of the arcaneness out
> of the mix. I have not got around to trying out a couple algos

But debloat is just like... way too much. And probably not very tuned for our
use case :-)

I'll be perfectly happy just doing _something_; I don't need a perfect
solution. We have one more night of streaming, and then the event is over. :-)

/* Steinar */
Homepage: http://www.sesse.net/

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