perf/x86/intel: Perform rotation on Intel CQM RMIDs
There are many use cases where people will want to monitor more tasks
than there exist RMIDs in the hardware, meaning that we have to perform
some kind of multiplexing.
We do this by "rotating" the RMIDs, and assigning an RMID to a waiting
event when the RMID becomes unused.
This scheme reserves one RMID at all times for rotation. When we need to
schedule a new event we give it the reserved RMID, pick a victim event
from the front of the global CQM list and wait for the victim's RMID to
drop to zero occupancy, before it comes the new reserved RMID.
The comments above __intel_cqm_rmid_rotate() have more details.
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
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