PMC.IAF(3) BSD Library Functions Manual PMC.IAF(3)NAMEpmc.iaf — measurement events for Intel fixed function performance coun‐
Performance Counters Library (libpmc, -lpmc)
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-func‐
tion PMCs present can be determined at runtime by using function
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.
Fixed-function PMCs support the following capabilities:
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
(Atom CPUs) Configure the PMC to count events on all logical pro‐
cessors 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:
(Fixed Function Counter 0) The number of instructions retired.
(Fixed Function Counter 1) The number of core cycles for which
the core is not halted.
(Fixed Function Counter 2) The number of reference cycles for
which the core is not halted.
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 speci‐
To measure the number of user instructions retired on all logical proces‐
sors in an Atom CPU, use the event specifier
SEE ALSOpmc(3), pmc.atom(3), pmc.core(3), pmc.core2(3), pmc.k7(3), pmc.k8(3),
pmc.p4(3), pmc.p5(3), pmc.p6(3), pmc.tsc(3), pmc_cpuinfo(3), pmclog(3),
The pmc library first appeared in FreeBSD 6.0.
The Performance Counters Library (libpmc, -lpmc) library was written by
Joseph Koshy ⟨jkoshy@FreeBSD.org⟩.
BSD November 14, 2008 BSD