NAME

       libpfm_intel_gnr - support for Intel GraniteRapids core PMU

SYNOPSIS

       #include <perfmon/pfmlib.h>

       PMU name: gnr
       PMU desc: Intel GraniteRapids

DESCRIPTION

       The library supports the Intel GraniteRapids core PMU. It should be noted that this PMU model only covers
       each core's PMU and not the socket level PMU.

       On Intel GraniteRapids, the number of generic counters depends on the Hyperthreading (HT) mode.

       The pfm_get_pmu_info() function returns the maximum number of generic counters in num_cntrs.

MODIFIERS

       The following modifiers are supported on Intel GraniteRapids processors:

       u      Measure at user level which includes privilege levels 1, 2, 3. This corresponds to PFM_PLM3.  This
              is a boolean modifier.

       k      Measure at kernel level which includes privilege level 0. This corresponds to PFM_PLM0.  This is a
              boolean modifier.

       i      Invert  the  meaning  of  the  event.  The counter will now count cycles in which the event is not
              occurring. This is a boolean modifier

       e      Enable edge detection, i.e., count only when there is a state transition from no occurrence of the
              event to at least one occurrence. This modifier must be combined with a counter mask modifier  (m)
              with a value greater or equal to one.  This is a boolean modifier.

       c      Set  the  counter  mask  value. The mask acts as a threshold. The counter will count the number of
              cycles in which the number of occurrences of the event is greater or equal to the threshold.  This
              is an integer modifier with values in the range [0:255].

       ldlat  Pass  a  latency  threshold  to  the  MEM_TRANS_RETIRED:LOAD_LATENCY  event.   This  is an integer
              attribute that must be in the range [1:65535]. It is required for this event.  Note that the event
              must be used with precise sampling (PEBS).

       intx   Monitor the event only when executing inside a transactional memory region (in tx). Event does not
              count otherwise. This is a boolean modifiers. Default value is 0.

       intxcp Do not count occurrences of the event when they are inside an aborted transactional memory region.
              This is a boolean modifier. Default value is 0.

       fe_thres
              This modifier is for the FRONTEND_RETIRED event only. It defines the period in core  cycles  after
              which  the  IDQ_*_BUBBLES  umask counts. It acts as a threshold, i.e., at least a period of N core
              cycles where the frontend did not deliver X uops. It can  only  be  used  with  the  IDQ_*_BUBBLES
              umasks.  If  not  specified,  the  default  threshold  value  is  1 cycle. the valid values are in
              [1-4095].

OFFCORE_RESPONSE events

       Intel GraniteRapids supports two encodings for offcore_response events. the library uses the generic  OCR
       event name to match Intel's definitions. However, the old OFFCORE_RESPONSE_0 and OFFCORE_RESPONSE_1 names
       are  still available for backward compatibility. It should be noted that OCR is not an architected event,
       therefore it can changed between processor generations.

       Those events need special treatment in the performance monitoring infrastructure because each event  uses
       an extra register to store some settings. Thus, in case multiple OCR events are monitored simultaneously,
       the operating system needs to manage the sharing of that extra register.

       The  OCR  events are exposed as a normal events by the library. The extra settings are exposed as regular
       umasks. The library takes care of encoding the events according to the underlying kernel interface.

       On Intel GraniteRapids, the event is treated as a regular event with a flat set of umasks to choose from.
       It is not possible to combine the various requests, supplier, snoop bits anymore. Therefore  the  library
       offers the list of validated combinations as per Intel's official event list.

Topdown via PERF_METRICS

       Intel  GraniteRapids supports the PERF_METRICS MSR which provides support for Topdown Level 1 and 2 via a
       single PMU counter. This special counter provides percentages of slots for each metric. This feature must
       be used in conjunction with fixed counter 3 which counts SLOTS in  order  to  work  properly.  The  Linux
       kernel exposes PERF_METRICS metrics as individual pseudo events counting in slots unit however to operate
       correctly all events must be programmed together. The Linux kernel requires all PERF_METRICS events to be
       programmed  as  a  single  event  group with the first event as SLOTS required. Example: '{slots,topdown-
       retiring,topdown-bad-spec,topdown-fe-bound,topdown-be-bound,topdown-heavy-ops,topdown-br-
       mispredict,topdown-fetch-lat,topdown-mem-bound}'. Libpfm4 provides  access  to  the  PERF_METRICS  pseudo
       events via a dedicated event called TOPDOWN_M. This event uses the pseudo encodings assigned by the Linux
       kernel  to PERF_METRICS pseudo events. Using these encodings ensures the kernel detects them as targeting
       the PERF_METRICS MSR. Note that libpfm4 only provides the encodings and that it is up the user  on  Linux
       to  group  them  and  order  them  properly  for  the perf_events interface. There exists generic counter
       encodings for most of the Topdown metrics and libpfm4 provides support for those via the  TOPDOWN  event.
       Note that all subevents of TOPDOWN_M use fixed counters which have, by definition, no actual event codes.
       The  library  uses  the  Linux  pseudo  event  codes  for them, even when compiled on non Linux operating
       systems.The same holds true for any fixed counters pseudo event exported by libpfm4.

AUTHORS

       Stephane Eranian <eranian@gmail.com>

                                                   June, 2024                                          LIBPFM(3)