LPC 2022 GPU BOF (user console and cgroups)

 At LPC 2022 we had a BoF session for GPUs with two topics.

Moving to userspace consoles:

Currently most mainline distros still use the kernel console, provided by the VT subsystem. We'd like to move to CONFIG_VT=n as the console and vt subsystem have historically been a source of bugs but are also nasty places for locking etc. It also can be the cause of oops going missing when it takes out the panic path with locking bugs stopping other paths from completely processing the oops (like pstore or serial).

 The session started discussing what things would like. Lennart gave a great summary of the work David did a few years ago and the train of thought involved.

Once you think through all the paths and things you want supported, you realise the best user console is going to be one that supports emojis and non-Latin scripts. This probably means you want a lightweight wayland compositor running a fullscreen VTE based terminal. Working back from the consequences of this means you probably aren't going to want this in systemd, and it should be a separate development.

The other area discussed was around the requirements for a panic/emergency kernel console, likely called drmlog, this would just be something to output to the display whenever the kernel panics or during boot before the user console is loaded.

cgroups for GPU

This has been an ongoing topic, where vendors often suggest cgroup patches, and on review told they are too vendor specific and to simplify and try again, never to try again. We went over the problem space of both memory allocation accounting/enforcement and processing restrictions. We all agreed the local memory accounting was probably the easiest place to start doing something. We also agreed that accounting should be implemented and solid before we start digging into enforcement. We had a discussion about where CPU memory should be accounted, especially around integrated vs discrete graphics, since users might care about the application memory usage apart from the GPU objects usage which would be CPU on integrated and GPU on discrete. I believe a follow-up hallway discussion also covered a bunch of this with upstream cgroups maintainer.

Comments

Post a Comment

Popular posts from this blog

On Rust, Linux, developers, maintainers

There's been a couple of mentions of Rust4Linux in the past week or two, one from Linus on the speed of engagement and one about Wedson departing the project due to non-technical concerns. This got me thinking about project phases and developer types. Archetypes: I will regret making an analogy, in an area I have no experience in, but let's give it a go with a road building analogy.   Let's sort developers into 3 rough categories. Let's preface by saying not all developers fit in a single category throughout their careers, and some developers can do different roles on different projects, or on the same project simultaneously. 1. Wayfinders/Mapmakers I want to go build a hotel somewhere but there exists no map or path. I need to travel through a bunch of mountains, valleys, rivers, weather, animals, friendly humans, antagonistic humans and some unknowns. I don't care deeply about them, I want to make a path to where I want to go. I hit a roadblock, I don't focus...
Read more

radv: vulkan av1 video decode status

The Khronos Group announced VK_KHR_video_decode_av1 [1], this extension adds AV1 decoding to the Vulkan specification. There is a radv branch [2] and merge request [3]. I did some AV1 work on this in the past, but I need to take some time to see if it has made any progress since. I'll post an ANV update once I figure that out. This extension is one of the ones I've been wanting for a long time, since having royalty-free codec is something I can actually care about and ship, as opposed to the painful ones. I started working on a MESA extension for this a year or so ago with Lynne from the ffmpeg project and we made great progress with it. We submitted that to Khronos and it has gone through the committee process and been refined and validated amongst the hardware vendors. I'd like to say thanks to Charlie Turner and Igalia for taking over a lot of the porting to the Khronos extension and fixing up bugs that their CTS development brought up. This is a great feature of having ...
Read more

anv: vulkan av1 decode status

 Vulkan Video AV1 decode has been released, and I had some partly working support on Intel ANV driver previously, but I let it lapse. The branch is currently [1]. It builds, but is totally untested, I'll get some time next week to plug in my DG2 and see if I can persuade it to decode some frames. Update: the current branch decodes one frame properly, reference frames need more work unfortunately. [1] https://gitlab.freedesktop.org/airlied/mesa/-/commits/anv-vulkan-video-decode-av1
Read more