jwboyer (jwboyer) wrote,

LPC 2015 Day 1

I have the privilege of attending the Linux Plumbers Conference in Seattle this week. This is by far my favorite conference. The talks and microconferences are all of high quality and the events are very well organized.

The first day is shared with LinuxCon, which lends itself to some talks that span both audiences. The first talk I attended with "Everything is a file descriptor" by Josh Triplett. Josh gave a great overview of why file descriptors are a great mechanism and some of the more recent system calls that have been added to give userspace the ability to write less crappy code. Things like timerfd, and signalfd allow userspace to avoid some of the awkwardness that comes with using the more traditional interfaces that UNIX has provided. He also described work on clonefd, which is a new system call to allow userspace to get a file descriptor tied to a task in the kernel. This will have some interested benefits, such as being able to pass the fd to a process that is not in your process hierarchy and being able to poll for child/task exit without hanging in waitpid. At the end Josh threw out some possible future additions that haven't been implemented. Overall a very well done talk.

Following that, I sat in on Steven Rostedt's talk on the RT patchset. I've seen this talk or a version of it around three times and I'm always highly entertained. Steven likes to pack a ton of information in his talks. The overall success of the RT patchset has been very good, and they are down to some of the final really hard bits. Some of them they actually need help with to figure out the best solution in the subsystem in question (like the VFS). One of the questions from the audience was about lessons learned working on the patchset, the issues they've fixed in mainline because of it, etc. Steven said that is a great idea for another talk, so I hope he writes that up. I would love to hear it.

THe afternoon session started off with an overview of ACPI and where some of the ACPI 6 features are coming into play. Things like low power idle and other PM related features look to be headed towards us in hardware, and ACPI is of course being adapted to work with this. Overall a good overview.

Following that I did a bit of hallway track and then went to Daniel Vetter's talk on screwing up (or how to not) ioctls. Working in the DRM layer has provided him with lots of experience over the past few years on how to properly design your code to make it easier to use. One of the main points that was stressed several times was having testcases for everything. This is fairly obvious, but he pointed out that the testcases are better written when you aren't looking at the code. If you just look at the data structures and create boundary cases based on that, with all kinds of crazy input, you will often catch cases that the code itself doesn't cover. He had a good amount to say and it was entertaining.

The traditional kernel panel was the wrap up for the day, but I skipped that to catch up on some work. Then it was off to the evening event at the Experience Music Project museum. This venue was amazing and had a variety of exhibits ranging from a guitar collection to Star Wars costumes. It was very cool and the food was excellent. After spending perhaps a bit more than I expected in the gift shop, it was back to the hotel to try and sleep off some of the weariness that comes from travel delays and cramming information into your head all day.

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