Tuesday, 06 January 2015
I promised to write about this a long time, ooops... :-)
Another ARM port in Debian - yay!
arm64 is officially a release architecture for Jessie, aka Debian version 8. That's taken a lot of manual porting and development effort over the last couple of years, and it's also taken a lot of CPU time - there are ~21,000 source packages in Debian Jessie! As is often the case for a brand new architecture like arm64 (or AArch64, to use ARM's own terminology), hardware can be really difficult to get hold of. In time this will cease to be an issue as hardware becomes more commoditised, but in Debian we really struggled to get hold of equipment for a very long time during the early part of the port.
First bring-up in Debian Ports
To start with, we could use ARM's own AArch64 software models to build the first few packages. This worked, but only very slowly. Then Chen Baozi and the folks running the Tianhe-2 supercomputer project in Guangzhou, China contacted us to offer access to some arm64 hardware, and this is what Wookey used for bootstrapping the new port in the unofficial Debian Ports archive. This has now become the normal way for new architectures to get into Debian. We got most of the archive built in debian-ports this way, and we could then use those results to seed the initial core set of packages in the main Debian archive.
Second bring-up - moving into the main Debian archive
By the time that first Debian bring-up was done, ARM was starting to produce its own "Juno" development boards, and with the help of my boss^4 James McNiven we managed to acquire a couple of those machines for use as official Debian build machines. The existing machines in China were faster, but for various reasons quite difficult to maintain as official Debian machines. So I set up the Junos as buildds just before going to DebConf in August 2014. They ran very well, and (for dev boards!) were very fast and stable. They built a large chunk of the Debian archive, but as the release freeze for Jessie grew close we weren't quite there. There was a small but persistent backlog of un-built packages that were causing us issues, plus the Juno machines are/were not quite suitable as porter boxes for Debian developers all over the world to use for debugging their packages on the new architecture.
More horsepower - Linaro machines
This is where Linaro came to our aid. Linaro's goal is to help improve Free and Open Source Software on ARM, and one of the more recent projects in Linaro is a cluster of servers that are made available for software developers to use to get early access to ARMv8 (arm64) hardware. It's a great way for people who are interested in this new architecture to try things out, port their software or indeed just help with the general porting effort.
As Debian is seen as such an important part of the FLOSS ecosystem, we managed to negotiate dedicated access to three of the machines in that cluster for Debian's use and we set those up in October, shortly before the freeze for Jessie. Andy Doan spent a lot of his time getting these machines going for us, and then I set up two of them as build machines and one as the porter box we were still needing.
With these extra machines available, we quickly caught up with the ever-busy "Needs-Build" queue and we've got sufficient build power now to keep things going for the Jessie release. We were officially added to the list of release architectures at the Cambridge mini-Debconf in November, and all is looking good now!
And in the future?
I've organised the loan of another arm64 machine from AMD for Debian to use for further porting and/or building. We're also expecting that more and more machines will be coming out soon as vendors move on from prototyping to producing real customer equipment. Once that's happened, more kit will be available and everybody will be able to have arm64-powered computers in the server room, on their desk and even inside their laptop! Mine will be running Debian Jessie... :-)
There's been a lot of people involved in the Debian arm64 bootstrapping at various stages, so many that I couldn't possibly credit them all! I'll highlight some, though. :-)
First of all, Wookey's life has revolved around this port for the last few years, tirelessly porting, fixing and hacking out package builds to get us going. We've had loads of help from other teams in Debian, particularly the massive patience of the DSA folks with getting early machines up and running and the prodding of the ftpmaster, buildd and release teams when we've been grinding our way through ever more package builds and dependency loops. We've also had really good support from toolchain folks in Debian and ARM, fixing bugs as we've found them by stressing new code and new machines. We've had a number of other people helping by filing bugs and posting patches to help us get things built and working. And (last but not least!) thanks to all the folks who've helped us beg and borrow the hardware to make the Debian arm64 port a reality.
Rumours of even more ARM ports coming soon are entirely scurrilous... *grin*