Delan Azabani

linux.conf.au 2014, day 4: Trent and the batteryists

LCA 2014 is really coming into its own now, and although it'd be great to finally get a chance to sleep, it's more regrettable that there's only one day left. Today's mandatory surprise was finding out that Rusty Russell was not simply a volunteer that held the newcomers' introduction.

It turns out that Rusty, or rather, Paul Russell, was not only the creator of CALU, the precursor to linux.conf.au before its name chnaged, but also the original author of iptables and netfilter in the Linux kernel. Pretty amazing stuff.

First up was my first time watching the engaging Trent Lloyd. It turns out, according to this Oracle support engineer and chairman of Australia's premier LAN party, that bigger numbers in my.cnf are not always better. Boosting the hundreds of available options to 'optimise' your database could lead to frequent OOM kills or worse, pathological cache invalidation performance.

Paul McKenney struggles to please energy efficiency worshippers, also known as battery users, while optimising scheduler interrupts in the Linux kernel towards reducing overhead from a 'bare metal' software configuration for the HPC crowd. Safely keeping track of which CPUs are actually idle without any race conditions turns out to be surprisingly difficult.

Petitboot: doing interesting things in your bootloader by Jeremy Kerr showed that typical bootloaders are far more than just loading a kernel from disk, jumping to it, and maybe providing a bit of UI in between. Modern boot code in firmwares and bootloaders have a large amount of code for things like network booting, disk drivers, basic filesystem support, iSCSI, a TCP/IP stack and more.

This seems incredibly familiar, almost like an operating system. So instead of having all of this redundancy, why not use a Linux kernel itself as the bootloader, and simply have just enough external code to jump to it? By doing so, Petitboot has all of the features of a Linux kernel, and can even efficiently boot the user's OS, given that it can be a kexec target.

However, the possibilities this opens are immense. You can now boot, say, a Linux kernel downloaded over HTTP, or FTP, or even BitTorrent. That'll surely save some resources by being distributed, right? One could even create a website for a friendly, online custom kernel configuration method, and dynamically serve the compiled kernels to Petitboot clients. Uh oh, I think I'm onto something here.

Luke managed to get Linus to sign his Macbook. I'm insanely jealous.

UCC member of at least 17 years and now a Debian Developer working at AWS, James Bromberger detailed the process of using Amazon S3 and Glacier to reliably, securely and efficiently host Debian images and packages, as well as the Debian snapshot archive, which includes every version of every package in history. I've managed to get a chance to help out with the web request frontend, where users can fetch from Glacier through S3 and EC2.

With more lightning talks, a D-Bus presentation by Lennart Poettering, the Rust programming language and TCP Tuning for the Web, I can't wait to see what the impending final day has to offer. Meanwhile, sleep is great; you should probably try it.