[Hello71]

PSI is exported by the kernel to track context switches: switch to idle process = io wait, switch to kswapd = mem wait, switch to other runnable process = cpu wait. these are already visible to the kernel, it just needs to increment some counters and expose those to userspace. you can get the perf counters with something like `perf stat -ae cache-misses sleep 60`, it doesn't need to be in /proc.

additionally, context switches are the same on everything that can run Linux, whereas PMU counters are highly CPU-specific (potentially even different in each CPU stepping), so given the current state of affairs, a generic interface would be very limited.