[Wylug-discuss] BBC speeds up TCP video streaming on Linux (paraphrase)

[Rob Speed]

It's actually the boys and girls three floors up from me in R+D.
I spoke to Stuart, and he's explained a little more:

"In answer to the question, I'm sure all three factors contribute to the performance gains. Instead of passing packets through the kernel stack, one by one, and copying all the payload data from user buffers to kernel buffers, we make a single call that switches maybe 500 packets from being under app ownership to driver ownership in situ - the data never moves. The kernel overhead per packet drops to near zero. Note that, despite the mention of TCP in The Register, we are working with RTP streams over UDP - no TCP involved.

We use netmap as the underlying technology, with various extra bits bolted on to suit our particular requirements. If you follow the links from the netmap project page, you can find a lot of interesting analysis and discussion of the technique:

 http://info.iet.unipi.it/~luigi/netmap/#a5c3

"

HTH
R.

________________________________________
From: Wylug-discuss [wylug-discuss-bounces at wylug.org.uk] on behalf of Graham Whaley [graham.whaley at gmail.com]
Sent: 15 October 2015 13:45
To: wylug-discuss at wylug.org.uk
Subject: [Wylug-discuss] BBC speeds up TCP video streaming on Linux     (paraphrase)

RobS, is this you and yours?

http://www.theregister.co.uk/2015/10/12/linux_networking_api_showing_its_age/

something we can discuss at the next meet maybe. I'd be interested if
it is just the buffer share/zero copy that gets the major speedup, or
the buffer batching, or the reduction in syscalls and context switches
- or a combination of all three.

If I remember I'll also bring along some hacker boards for folks to
stare at - an early Minnow version (now generally surpassed), an ARM64
Dragon 410c I just won and a MIPS CI20 for comparison. All run Linux.

 Graham

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