Network Storage: Loopback ext3 on NFS? Really? Thu, Apr 22. 2010
One interesting find I made while working with the Seneca students on Fedora ARM was that a loopback filesystem hosted on top of an NFS share can outperform the NFS share. Yes, it's counter-intuitive, because that would seem to introduce additional layers of processing, but I think it makes sense.
When using NFS, file metadata management is performed by NFS. When loopback-mounting a filesystem in a file hosted on NFS, the file metadata management takes place entirely on the local system -- NFS merely provides a data store. In this sense, it's not much different from iSCS, because the loopback filesystem can't be readily accessed by two separate hosts at once.
In fact, on a small ARM system such as an OpenRD-Client, loopback-ext3-on-NFS over GigE handily outperforms both Class 6 SD and a local USB-PATA drive.
Why not just use iSCSI? Well, for reasons I haven't yet determined, the Fedora iSCSI initiator doesn't work reliably on ARM-- under heavy load, it sends invalid opcodes to the target. This sounds like an alignment issue, but alignment fixups don't cure it. Investigation continues...
Seneca and the Fedora ARM Secondary Architecture Thu, Apr 22. 2010
ARM processors power the digital mobile age. Billions are produced per year, ending up in the majority of cellphones as well as in e-book readers, plug computers, the OLPC XO 1.75, tablets, netbooks, intelligent RJ-45 network jacks, and even microSD cards.
The Fedora ARM Secondary Architecture project has done a great job of porting Fedora releases to ARM. To assist this initiative, this semester's Software Build and Release course at Seneca (SBR600) put together a new Koji build farm for the ARM architecture in preparation for using koji-shadow to follow the primary architectures. It's been a fascinating and challenging project -- working with cross-compilers, emulators, and hardware with much smaller configurations than standard PCs. A large amount of effort was spent benchmarking various configurations to determine optimal memory and storage arrangements and to compare emulated vs. hardware ARM performance to guide the configuration of the build farm.
So now we're at the end of the semester. Where do things stand?
- We have a working Koji build system, with two hardware builders plus emulated (VM) builders
- Since we're at the end of the semester, things will be quiet for the next week and a half, but then we've hired a graduate to work on this full-time (intros coming up shortly )
What's next? In May-June we expect to:
Do you have important data or software on CDOT machines? Thu, Apr 8. 2010
We're about to reconfigure a number of machines in CDOT. If you have any critical data on these machines, you need to back it up or move it before exam week (April 18).
These machines will be updated (new disks) and/or reinstalled and/or moved:
These machines will not be reinstalled (yet), but will probably be moved:
...but even on those machines, it would be a great idea to back up your stuff!
Running Fedora-ARM in emulation under virsh Thu, Mar 4. 2010
The Fedora qemu-system-arm package provides pretty good ARM processor emulation, which can be used to run the Fedora ARM secondary architechture. This is an easy way to get started working with ARM -- for example, while waiting for your plugcomputer, beagleboard, or OLPC XO 1.75 to arrive
The previous wiki notes on using ARM with QEMU didn't cover using qemu-system-arm under libvirt management. This meant that you couldn't easily take advantage of libvirt benefits such as automatic network setup (with DHCP and NAT), the virt-manager GUI tool, guest autostart, or disconnection/reconnection to the console.
I've updated https://fedoraproject.org/wiki/Architectures/ARM/HowToQemu to include some basic notes on setting this up, and provided some files to simplify and speed up the process. Jump in and join Fedora-ARM, the water's nice!
View Source Button, Test of Concept Tue, Nov 24. 2009
Alexander Larsson answered my Dear Lazyweb on finding a PID given a Window ID, to implement Richard Jones' View Source Button idea. I hacked up a tiny bash script to see what kind of info we could easily get about a window. Running that script and clicking on the Gnome calculator, I see:
Click on a window. Avoid clicking on a window border.
Upstream URL: http://directory.fsf.org/gcalctool.html
Fedora release: 12
Bugzilla search: https://bugzilla.redhat.com/buglist.cgi?query_format=advanced&classification=Fedora&product=Fedora&component=gcalctool&version=12
PackageDB page: https://admin.fedoraproject.org/pkgdb/packages/name/gcalctool
Transifex page: (None)
There's a lot more that needs to be handled -- for example, clicking on a script window reports the interpreter instead of the script, clicking on a window border reports nothing, clicking on the window of a consolehelper'd app fails on access to /proc/$PID/exe, and clicking on a terminal window reports the terminal program instead of the character-mode app that is running (obviously).
All of these can be solved fairly easily, and the idea looks workable! As I noted in a commend on Richard's original post, it would be cool to make this View Source applet capable of taking the user to the pkgdb page, a source code browser (I'm thinking DXR, once we get it indexing all of Fedora), a bugzilla search, the upstream web page, or the translate.fedoraproject.org page; or, if the user chose, the applet could download and install the .src.rpm.
StudentProject keyword in Fedora Bugzilla Wed, Nov 11. 2009
One challenge of teaching inside an open source community is finding projects which are appropriately for students to work on: they shouldn't be really trivial, because that won't provide a challenge or allow the student to engage with the community; they can't be huge, or the student won't finish them within the semester; and they can't be blockers or part of the critical path to a release, because the student may not be able to complete the project on the community's timeline.
My colleague David Humphrey introduced a new keyword into the Mozilla bugzilla tracker last spring, and it has been successfully used to identify many potential student projects (108 at the time of writing).
Good ideas are worth copying -- and since I'm bringing students into the Fedora community, and the POSSE-APAC professors will bring even more, I asked Dave Lawrence to add the StudentProject keyword to the Fedora/Red Hat bugzilla (thanks Dave and Paul!).