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g2k16 Hackathon Report: Alexander Bluhm on mbufs and more

Sat, 17 Sep 2016 12:18:36 GMT

Alexander Bluhm (bluhm@) contributed our next report (which even includes a picture):

Big plans what to do at a hackathon don't work. There is always something unexpected that requires your attention. So I was expecting the unexpected. The TCP send performance has dropped to a very low throughput in some environments. It was pretty clear that it was related with claudio@'s change to speed up TCP by using large mbufs instead of chaining small ones. Mbufs are used inside the kernel to hold network data. Using a lot of them requires many allocations and frees. This can be avoided by using larger mbufs. But why did it get slower? Together with mikeb@ we found out that it was related to the mbuf space limit in the socket buffer. One large mbuf filled the send buffer, so no new mbufs could be inserted until TCP received the acknowledgements for everything. So the sliding window algorithm with mbufs cycling through the socket buffer did not work anymore. After identifying the problem, the fix was easy, just increase the default socket buffer mbuf size limit.


g2k16 Hackathon Report: Patrick Wildt on arm, LLVM and other progress

Thu, 15 Sep 2016 21:09:24 GMT

The g2k16 hackathon must have been a really great one, because here is yet another report, this time from Patrick Wildt, who writes:

I knew that if I had any plans for the hackathon, they would have been thrown out of the window as soon as I arrived there. That was a good plan actually, since exactly that happened.

g2k16 Hackathon Report: Martin Pieuchot on USB stack and routing progress, more

Thu, 15 Sep 2016 10:56:23 GMT

The g2k16 hackathon reports keep coming, and we love it! In this fresh report, Martin Pieuchot writes,

Since some years now, I cannot attend a hackathon without having to deal with a USB problem. It's generally a bug that one of the hackers in the room can expose with his hardware. But in Cambridge it was different!

Ted Unangst on "doas mastery"

Tue, 13 Sep 2016 10:14:38 GMT

Ted Unangst (tedu@) has written an item regarding doas:

It’s been a year since the introduction of doas, so it’s clearly time to write a book. Or maybe a pamphlet.

See his flak entry for the full story (and bear in mind he's referring to -current at the time of writing).