tools/power turbostat: Add L2 cache statistics

tools/power turbostat: Add L2 cache statistics

version 2026.02.04

Add support for L2 cache statistics: L2MRPS and L2%hit
L2 statistics join the LLC in the "cache" counter group.

While the underlying LLC perf kernel support was architectural,
L2 perf counters are model-specific:

Support Intel Xeon -- Sapphire Rapids and newer.
Support Intel Atom -- Gracemont and newer.
Support Intel Hybrid -- Alder Lake and newer.

Example:

alder-lake-n$ sudo turbostat --quiet --show CPU,Busy%,cache my_workload
CPU	Busy%	LLCMRPS	LLC%hit	L2MRPS	L2%hit
-	49.82	1210	85.02	2909	31.63
0	99.14	322	88.89	767	32.38
1	0.91	1	32.47	1	18.86
2	0.20	0	40.78	0	23.34
3	99.17	295	81.79	706	31.89
4	0.68	1	58.71	1	15.61
5	99.16	299	85.65	726	31.32
6	0.08	0	45.35	0	31.71
7	99.21	293	83.63	707	30.92

where "my_workload" is a wrapper for a yogini workload
that has 4 fully-busy threads with 2MB working set each.

Note that analogous to the system summary for multiple LLC systems,
the system summary row for the L2 is the aggregate of all CPUS in the
system -- there is no per-cache roll-up.

Signed-off-by: Len Brown <len.brown@intel.com>