Hello, I understand correctly the principle of generic / fixed counters, but I’m wondering if there is a way to detect automatically whether an event corresponds to a fixed counter.
I saw it was to possible to retrieve theirs numbers with libpfm, but it does not help to classify them in two subsets. Is this concept specific to Intel processor? I cannot find any documentation about fixed counters on AMD or ARM for example. For example, on my Xeon processor (Nehalem), I have 4 generic counters (HT on) and 2 fixed counters (3 - 1 because of NMI watchdog). For instance, I suppose that the events mapped to the fixed counters are: 0xC0 (INSTRUCTION_RETIRED) and 0x300 (UNHALTED_REFERENCE_CYCLES) based on my experiments. Can I say that these events and 0x3c (UNHALTED_CORE_CYCLES) are mapped to the fixed counters for Intel processors? Or, is there a way to find them automatically? Are they common for Intel processors? Many thanks, Command output: dmesg | grep -A 15 Nehalem [ 0.171273] Performance Events: PEBS fmt1+, 16-deep LBR, Nehalem events, Intel PMU driver. [ 0.171278] perf_event_intel: CPU erratum AAJ80 worked around [ 0.171279] perf_event_intel: CPUID marked event: 'bus cycles' unavailable [ 0.171281] ... version: 3 [ 0.171282] ... bit width: 48 [ 0.171282] ... generic registers: 4 [ 0.171283] ... value mask: 0000ffffffffffff [ 0.171284] ... max period: 000000007fffffff [ 0.171285] ... fixed-purpose events: 3 [ 0.171286] ... event mask: 000000070000000f [ 0.172934] x86: Booting SMP configuration: [ 0.186247] NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter. Maxime Colmant PhD Student - ADEME / University Lille 1 Spirals Team - INRIA Lille, bât. B Tel. : +33(0) 3 59 35 87 79 Perso. : +33(0) 6 24 00 12 35 http://mcolmant.github.io <http://mcolmant.github.io/>
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