Originally Posted by syg00
I see no advantage in what you are attempting to do - but feel free to dive into the code; you may need some time and patience.
He's looking to make a trade-off that gives up some CPU cycles to ensure that system processes aren't at all affected by any CPU-intense user process (encoding video, for example).
For an example, assume four CPUs. Under a normal OS with decent SMP support, when enough processes exist to eat 100% of CPU on all 4 CPUs, the system processes will be fighting with the userland processes for CPU time. This solution allows the use of all 400% (yes, I know it should be 100, but this better illustrates the situation for me) of CPU cycles to be used, so it is effecient in that it doesn't waste any CPU cycles.
The scenario tryon16 is looking for would allow the userland processes to eat up 300% of CPU cycles, while reserving the last CPU solely for system processes. In this way, the system processes aren't fighting for CPU cycles with the userland processes. This comes at the cost of not using all of your CPU cycles. Say that system processes only used 2% of a given processor's available cycles, then the max usage would be 302% compared to the 400% of the first scenario.
Obviously, the trade-off is guaranteeing CPU availability to system processes at the cost of inefficient CPU usage.
With all of that said, I would tend to agree that I don't think this would be useful. Even if you guarantee CPU availability to your system processes, as a user, you'll still be waiting on the userland processes. You won't be speeding things up, just slowing them down by offering less CPU for use. Furthermore, it takes a hell of a lot to get four cores to max out all CPU usage. Finally, when a userland process does something that requires system process (reading from disk, for example), it won't be using any CPU until it gets the information from the disk, thus kind of forcing the necessary system process(es) into the spotlight.
Just my two cents. I could be completely wrong.
As far as running like Cell does, that's a bit different than what I just described, but since there are a few Linux distros that run on PS3, it seems like it would be worthwhile to look at the architecture-specific code and clone that.