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>

Author: lenb

tools/power/x86/turbostat/turbostat.8

@@ -163,7 +163,11 @@ The system configuration dump (if --quiet is not used) is followed by statistics
 .PP
 \fBLLCMRPS\fP Last Level Cache Millions of References Per Second.  For CPUs with an L3 LLC, this is the number of references that CPU made to the L3 (and the number of misses that CPU made to it's L2).  For CPUs with an L2 LLC, this is the number of references to the L2 (and the number of misses to the CPU's L1).  The system summary row shows the sum for all CPUs.  In both cases, the value displayed is the actual value divided by 1,000,000.  If this value is large, then the LLC%hit column is significant.  If this value is small, then the LLC%hit column is not significant.
 .PP
-\fBLLC%hit\fP Last Level Cache Hit Rate %.  Hit Rate Percent = 100.0 * (References - Misses)/References.  The system summary row shows the weighted average for all CPUs (100.0 * (Sum_References - Sum_Misses)/Sum_References).
+\fBLLC%hit\fP Last Level Cache Hit Rate %.  Hit Rate Percent = 100.0 * Hits/References.  The system summary row shows the weighted average for all CPUs (100.0 * Sum_Hits/Sum_References).
+.PP
+\fBL2MRPS\fP Level-2 Cache Millions of References Per Second.  For CPUs with an L2 LLC, this is the same as LLC references.  The system summary row shows the sum for all CPUs.  In both cases, the value displayed is the actual value divided by 1,000,000.  If this value is large, then the L2%hit column is significant.  If this value is small, then the L2%hit column is not significant.
+.PP
+\fBL2%hit\fP Level-2 Cache Hit Rate %.  Hit Rate Percent = 100.0 * Hits/References.  The system summary row shows the weighted average for all CPUs (100.0 * (Sum_Hits)/Sum_References).
 .PP
 \fBC1, C2, C3...\fP The number times Linux requested the C1, C2, C3 idle state during the measurement interval.  The system summary line shows the sum for all CPUs.  These are C-state names as exported in /sys/devices/system/cpu/cpu*/cpuidle/state*/name.  While their names are generic, their attributes are processor specific. They the system description section of output shows what MWAIT sub-states they are mapped to on each system.  These counters are in the "cpuidle" group, which is disabled, by default.
 .PP