It’s been quite a long time since my last report so I think it is a good time to describe what I have been doing in the last two months. The main scheduler logic has been completed and now I am concentrating mainly on bug fixes, adjusting tunables and some minor improvements. I also removed gSchedulerLock, a spinlock I mentioned in my last post, and replaced it with more fine grained locking. An new interfaces for cpufreq and cpuidle modules has been created together with a cpufreq module for Intel Sandy Bridge or newer cores and cpuidle module for all processors that support C-states and invariant TSC. Furthermore, IRQs (including MSI) can be now directed to an arbitrary logical processor. Implementation of inter-processor interrupts has been improved so that it avoids acquiring any lock if it is not necessary and supports multicast interrupts. And, last but not least, 8 processor limit has been removed.
First things first, I have introduced load tracking. Loads of each logical processor, core as well as loads produced by each thread and IRQ are monitored by the scheduler, which then uses that information to make all kinds of decisions. We have already keep track of how much time CPU spends doing useful work and how much CPU time thread consumes so extending it to compute load was a minor change. Knowing the load of all cores and the load a thread has been producing so far scheduler may attempt to choose the perfect core for a thread.
This is a companion discussion topic for the original entry at https://www.haiku-os.org/blog/pawe%C5%82_dziepak/2013-12-20_haiku_meets_9th_processor/