# libpfm_intel_snb

## 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**
    


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