NAME

pmc.iaf —

measurement events for Intel fixed function performance counters.

LIBRARY

Performance Counters Library (libpmc, -lpmc)

SYNOPSIS

#include <pmc.h>

DESCRIPTION

Intel fixed-function PMCs are present in CPUs that conform to version 2 or later of the Intel Performance Measurement Architecture. Each fixed-function PMC measures a specific hardware event. The number of fixed-function PMCs implemented in a CPU can vary. The number of fixed-function PMCs present can be determined at runtime by using function pmc_cpuinfo(3).

Intel fixed-function PMCs are documented in Volume 3: System Programming Guide, IA-32 Intel(R) Architecture Software Developer's Manual, Order Number 253669-027US, Intel Corporation, July 2008.

PMC Capabilities

Fixed-function PMCs support the following capabilities:

Capability	Support
PMC_CAP_CASCADE	No
PMC_CAP_EDGE	No
PMC_CAP_INTERRUPT	Yes
PMC_CAP_INVERT	No
PMC_CAP_READ	Yes
PMC_CAP_PRECISE	No
PMC_CAP_SYSTEM	Yes
PMC_CAP_TAGGING	No
PMC_CAP_THRESHOLD	No
PMC_CAP_USER	Yes
PMC_CAP_WRITE	Yes

Class Name Prefix

These PMCs are named using a class name prefix of “iaf-”.

Event Qualifiers (Fixed Function PMCs)

These PMCs support the following modifiers:

os: Configure the PMC to count events occurring at ring level 0.
usr: Configure the PMC to count events occurring at ring levels 1, 2 or 3.
anythread: (Atom CPUs) Configure the PMC to count events on all logical processors sharing a processor core. The default is to count events on the current logical processor.

If neither of the “os” or “usr” qualifiers are specified, the default is to enable both.

Event Specifiers (Fixed Function PMCs)

The fixed function PMCs are selectable using the following event names:

INSTR_RETIRED.ANY: (Fixed Function Counter 0) The number of instructions retired.
CPU_CLK_UNHALTED.CORE: (Fixed Function Counter 1) The number of core cycles for which the core is not halted.
CPU_CLK_UNHALTED.REF: (Fixed Function Counter 2) The number of reference cycles for which the core is not halted.

EXAMPLES

To measure the number of core cycles for which the core was not halted use the event specifier “iaf-cpu-clk-unhalted.core”.

To measure the number of user instructions retired use the event specifier “iaf-instr-retired.any,usr”.

To measure the number of user instructions retired on all logical processors in an Atom CPU, use the event specifier “iaf-instr-retired.any,usr,anythread”.

HISTORY

The pmc library first appeared in FreeBSD 6.0.

AUTHORS

The Performance Counters Library (libpmc, -lpmc) library was written by Joseph Koshy <jkoshy@FreeBSD.org>.