Comment by cwillu 10 months ago
Without the RT patchset, I can run one or two instruments at a 3ms latency, if I don't do anything else at all on my computer.
With it, I routinely have 6 instruments at 1ms, while having dozens of chrome windows open and playing 3d shooters without issue.
It's shocking how much difference it makes over the regular (non-rt) low latency scheduler.
It's every so slightly slower, but the difference is negligible and won't be noticed on a desktop machine. These days, I just run the (Debian) real-time kernel as a matter of course on my everyday machine.
I haven't objectively tested it, but my feeling is that it actually makes for a nicer user experience. Sometimes Gnome can briefly freeze or feel sluggish (presumably the CPU is off doing something) and I feel that the RT kernel does away with this. It could be a placebo effect though.
> It's every so slightly slower
in what way? I'd say responsiveness is more important to the desktop than raw performance and from my experience with nearly 2 decades of using Linux desktops, responsiveness has never been great.
If I'm switching between windows whilst encoding a video in the background, the window manager should have instant priority even if it means starving the background task of some CPU time. on GNOME this is quite bad, run a very heavy task (e.g. AI) in the background and the desktop will start to suffer.
I doubt that RT makes a nicer user experience on desktops. You are probably better of switching to another desktop-oriented scheduler.
Not really any harm in trying, but definitely note that the trail marked “trying scheduler changes to see if it improves desktop performance” is strewn with skeletons, the ghosts thereof haunt audio forums sayings things like “[ghostly] oooooohhhh, the sound is so much clearer now that I put vibration dampeners under my usb audio interface”.
The reason I wrote my original comment is precisely because “audio xruns at a higher latency with lower system load” is a very concrete measure of improvement that I can't fool myself about, including effects like “the system runs better when freshly booted for a while” that otherwise bias the judgements of the uninitiated towards “…and therefore the new kernel improved things!”
There isn't much on a desktop that is sensitive to latency spikes on the order of a couple ms, which a stock kernel should already be able to maintain.
6 instruments at 1ms, that's great! Are these MIDI instruments or audio in? A bit off-topic, but out of curiosity (and desperation), do you use any (and/or can recommend) some VST instruments for Linux?
Do you experience any downsides running the RT scheduler?
Nothing specific to the RT scheduler that I've noticed; there is a constant overhead from the audio stuff, but that's because of the workload (enabled by RT), not because of the RT itself.
My usual setup has 2 PianoTeq (physically modelled piano/electric piano/clavinet) instances, 3 SurgeXT instances (standard synthesizer), a setBfree (Tonewheel/hammond simulator) instance, and a handful of sequencers and similar for drums, as well as a bunch of routing and compressors and such.
Wait, so should casual desktop Linux users try this out too? I assumed there must be some trade-off to using RT?