Ubuntu Manpage: libpfm_intel_snb - support for Intel Sandy Bridge core PMU

Provided by: libpfm4-dev_4.13.0+git99-gc5587f9-1_amd64

NAME

       libpfm_intel_snb - support for Intel Sandy Bridge core PMU

SYNOPSIS

       #include <perfmon/pfmlib.h>

       PMU name: snb
       PMU desc: Intel Sandy Bridge
       PMU name: snb_ep
       PMU desc: Intel Sandy Bridge EP

DESCRIPTION

       The  library supports the Intel Sandy Bridge core PMU. It should be noted that this PMU model only covers
       each core's PMU and not the socket level PMU. For that refer to the Sandy Bridge uncore PMU support.

       On Sandy Bridge, the number of generic counters depends on the Hyperthreading (HT) mode.  When HT is  on,
       then  only  4  generic counters are available. When HT is off, then 8 generic counters are available. The
       pfm_get_pmu_info() function returns the maximum number of generic counters in num_cntrs.

MODIFIERS

The following modifiers are supported on Intel Sandy Bridge 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].

t Measure on both threads at the same time assuming hyper-threading is enabled. This is a boolean
modifier.

ldlat Pass a latency threshold to the MEM_TRANS_RETIRED:LATENCY_ABOVE_THRESHOLD 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).

OFFCORE_RESPONSE events

Intel Sandy Bridge provides two offcore_response events, like Intel Westmere. They 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 kernel 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 Sandy Bridge, the umasks are divided into three categories: request, supplier and snoop. The
user must provide at least one umask for each category. The categories are shown in the umask
descriptions.

There is also the special response umask called ANY_RESPONSE. When this umask is used then it overrides
any supplier and snoop umasks. In other words, users can specify either ANY_RESPONSE OR any combinations
of supplier + snoops.

In case no supplier or snoop is specified, the library defaults to using ANY_RESPONSE.

For instance, the following are valid event selections:

OFFCORE_RESPONSE_0:DMND_DATA_RD:ANY_RESPONSE

OFFCORE_RESPONSE_0:ANY_REQUEST

OFFCORE_RESPONSE_0:ANY_RFO:LLC_HITM:SNOOP_ANY

But the following are illegal:

OFFCORE_RESPONSE_0:ANY_RFO:LLC_HITM:ANY_RESPONSE

OFFCORE_RESPONSE_0:ANY_RFO:LLC_HITM:SNOOP_ANY:ANY_RESPONSE

AUTHORS