LIBPFM(3)

NAME
libpfm_intel_tmt - support for Intel Tremont core PMU

SYNOPSIS
#include <perfmon/pfmlib.h>

PMU name: tmt
PMU desc: Intel Tremont

DESCRIPTION
The library supports the Intel Tremont core PMU.

MODIFIERS
The following modifiers are supported on Intel Tremont 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].

OFFCORE_RESPONSE events
Intel Tremont provides two offcore_response events: OFFCORE_RESPONSE_0 and OFFCORE_RESPONSE_1. The OCR event is aliased to OFFCORE_RESPONSE_0.

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

On Intel Tremont, it is not possible to combine the request, supplier, snoop, fields anymore to avoid invalid combinations. As such, the umasks provided by the library are the only ones supported and validated.

AUTHORS
Stephane Eranian <eranian@gmail.com>