|
HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | MODIFIERS | OFFCORE_RESPONSE events | Topdown via PERF_METRICS | AUTHORS | COLOPHON |
|
|
|
LIBPFM(3) Linux Programmer's Manual LIBPFM(3)
libpfm_intel_icl - support for Intel IceLake core PMU
#include <perfmon/pfmlib.h>
PMU name: icl
PMU desc: Intel IceLake
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.
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].
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.
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
acces 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.
Stephane Eranian <eranian@gmail.com>
This page is part of the perfmon2 (a performance monitoring
library) project. Information about the project can be found at
⟨http://perfmon2.sourceforge.net/⟩. If you have a bug report for
this manual page, send it to perfmon2-devel@lists.sourceforge.net.
This page was obtained from the project's upstream Git repository
⟨git://git.code.sf.net/p/perfmon2/libpfm4 perfmon2-libpfm4⟩ on
2025-02-02. (At that time, the date of the most recent commit
that was found in the repository was 2025-01-27.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
August, 2019 LIBPFM(3)
|
HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|