4 ms·

I doubt they wanna run an RT kernel in SteamOS. There are severe costs to doing so.

the8472 2y ago
I assume the realtime patches brought some improvements you'll get even without compiling a hard realtime kernel. There's a whole bunch of CONFIG_PREEMPT_* options.
- sph 2y ago
  Yeah, I've been running my Fedora workstation with preempt=full for years now.
onli 2y ago
Are there some benchmarks for that, or a good discussion somewhere? Because I was wondering about that myself. RT kernel sounds at first like it may help achieve better latency in games, but then you are so deep in the stack and depending on overall performance, that the costs of RT mode might hurt much more than one would gain. But I don't really know how that plays out in practice.
- BlarfMcFlarf 2y ago
  I don’t know. My understanding though is that RT Linux adds predicability at the cost of throughput. For games where CPU throughput isn’t important (like an action game where most of the work is pushed off onto the GPU) this would maybe help. Someone could certainly try. But for other games like many strategy games and simulations where the CPU is a limiting factor, there would likely be a cost. The problem is that it’s not a free win, and games are very varied. But theoretically, on something like a console, you could offer choice.
- pdpi 2y ago
  My understanding is that real-time isn't so much about lower latency (though that is also desirable), but rather about predictable, bounded latency. For the purposes of gaming, no amount of predictability at the kernel level will reduce the amount of work you need to perform to draw a frame, and that is the real limiting factor for most games.
  - murderfs 2y ago
    > For the purposes of gaming, no amount of predictability at the kernel level will reduce the amount of work you need to perform to draw a frame, and that is the real limiting factor for most games. It all depends on what you're trying to optimize for. You can maximize raw framerate numbers by having an unlimited frame queue depth, but it'll feel like shit because you won't have even frame pacing and your input latency will vary wildly. The ideal scenario in gaming is for your draw time to be perfectly deterministic, and be able to schedule things so you can read input and do your render calls just before vsync.

I assume the realtime patches brought some improvements you'll get even without compiling a hard realtime kernel. There's a whole bunch of CONFIG_PREEMPT_* options.

sph 2y ago
Yeah, I've been running my Fedora workstation with preempt=full for years now.

onli 2y ago

Are there some benchmarks for that, or a good discussion somewhere? Because I was wondering about that myself. RT kernel sounds at first like it may help achieve better latency in games, but then you are so deep in the stack and depending on overall performance, that the costs of RT mode might hurt much more than one would gain. But I don't really know how that plays out in practice.

BlarfMcFlarf 2y ago
I don’t know. My understanding though is that RT Linux adds predicability at the cost of throughput. For games where CPU throughput isn’t important (like an action game where most of the work is pushed off onto the GPU) this would maybe help. Someone could certainly try. But for other games like many strategy games and simulations where the CPU is a limiting factor, there would likely be a cost. The problem is that it’s not a free win, and games are very varied. But theoretically, on something like a console, you could offer choice.
pdpi 2y ago
My understanding is that real-time isn't so much about lower latency (though that is also desirable), but rather about predictable, bounded latency. For the purposes of gaming, no amount of predictability at the kernel level will reduce the amount of work you need to perform to draw a frame, and that is the real limiting factor for most games.
- murderfs 2y ago
  > For the purposes of gaming, no amount of predictability at the kernel level will reduce the amount of work you need to perform to draw a frame, and that is the real limiting factor for most games. It all depends on what you're trying to optimize for. You can maximize raw framerate numbers by having an unlimited frame queue depth, but it'll feel like shit because you won't have even frame pacing and your input latency will vary wildly. The ideal scenario in gaming is for your draw time to be perfectly deterministic, and be able to schedule things so you can read input and do your render calls just before vsync.