Flying Fox wrote:Things like pro audio apps may be spending a lot of time waiting for the audio to come in. When waiting for I/O, the OS is basically idle so the CPU may choose to go to deeper sleep states (under the Balanced profile). You can't really have the app keep hogging the CPU just to keep it awake either, because that is just an ineffective use of CPU power (the reverse problem). In this case, the wakeup time just seems to be not fast enough for this particular use case, and the app would be forced to catch up, causing stutters.
If it's set to record, it's recording whatever is coming in on the inputs even if what's coming in is (near) silence.
In one of my previous posts I mentioned other reasons the CPU usage might be highly variable though. In a multi-track project with lots of instruments and effects plugins there's a lot going on and the load will vary as things switch in and out during mixing/playback.
Edit: FWIW I've played around a little bit with Rosegarden (DAW application for Linux), and yes there are potential issues with power management and high resolution system timer settings (HPET/TSC/ACPI) there too. In order to get smooth, glitch-free operation, things need to be "just so".
Flying Fox wrote:Re: RTOS - is QNX considered a real one? That's another big name that came to mind.
Yeah, QNX is (or was) another one. They used to be a major player; IIRC Blackberry acquired them at some point. Have they managed to kill it yet?
Edit: Looks like QNX has a significant presence in automotive. I expect Blackberry will eventually sell them off, or perhaps even morph into a business where developing/supporting QNX is their primary business model (since they're obviously an also-ran in the smartphone market at this point).
VxWorks (now owned by Intel) is another big one.