NAME¶
libpfm_intel_nhm - support for Intel Nehalem core PMU
SYNOPSIS¶
#include <perfmon/pfmlib.h>
PMU name: nhm
PMU desc: Intel Nehalem
PMU name: nhm_ex
PMU desc: Intel Nehalem EX
DESCRIPTION¶
The library supports the Intel Nehalem core PMU. It should be noted that this
PMU model only covers the each core's PMU and not the socket level PMU. It is
provided separately. Support is provided for the Intel Core i7 and Core i5
processors.
MODIFIERS¶
The following modifiers are supported on Intel Nehalem 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_INST_RETIRED:LATENCY_ABOVE_THRESHOLD
event. This is an integer attribute that must be in the range [3:65535].
It is required for this event. Note that the event must be used with
precise sampling (PEBS).
OFFCORE_RESPONSE event¶
The library is able to encode the OFFCORE_RESPONSE_0 event. This is a special
event because it needs a second MSR (0x1a6) to be programmed for the event to
count properly. Thus two values are necessary. The first value can be
programmed on any of the generic counters. The second value goes into the
dedicated MSR (0x1a6).
The OFFCORE_RESPONSE event is exposed as a normal event with several umasks
which are divided in two groups: request and response. The user must provide
at least one umask from each group. For instance,
OFFCORE_RESPONSE_0:ANY_DATA:LOCAL_DRAM.
When using
pfm_get_event_encoding(), two 64-bit values are returned. The
first value corresponds to what needs to be programmed into any of the generic
counters. The second value must be programmed into the dedicated MSR (0x1a6).
When using an OS-specific encoding routine, the way the event is encoded is OS
specific. Refer to the corresponding man page for more information.
AUTHORS¶
Stephane Eranian <eranian@gmail.com>