Introduce an index mapping between CPUs and their LLCs. This provides
a roughly continuous per LLC index needed for cache-aware load balancing in
later patches.
The existing per_cpu llc_id usually points to the first CPU of the
LLC domain, which is sparse and unsuitable as an array index. Using
llc_id directly would waste memory.
With the new mapping, CPUs in the same LLC share an approximate
continuous id:
per_cpu(llc_id, CPU=0...15) = 0
per_cpu(llc_id, CPU=16...31) = 1
per_cpu(llc_id, CPU=32...47) = 2
...
Note that the LLC IDs are allocated via bitmask, so the IDs may be
reused during CPU offline->online transitions.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Originally-by: K Prateek Nayak <kprateek.nayak@amd.com>
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/047ef46339e4db497b54a89940a7ebedf27fcf28.1775065312.git.tim.c.chen@linux.intel.com
b5ea300a17