NAME

       libpfm_intel_icl - support for Intel IceLake core PMU

SYNOPSIS

       #include <perfmon/pfmlib.h>

       PMU name: icl
       PMU desc: Intel IceLake

DESCRIPTION

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

       On IceLake, 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 IceLake 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  IceLake  supports  two  encodings  for  offcore_response  events. In the library, these are called
       OFFCORE_RESPONSE_0 and OFFCORE_RESPONSE_1.

       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 offcore_response events are monitored
       simultaneously, the operating system needs to manage the sharing of that extra register.

       The offcore_response 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  IceLake  unlike  older  processors, 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 Icelake supports the PERF_METRICS MSR which provides support for Topdown Level 1 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>

                                                  August, 2019                                         LIBPFM(3)