NAME
pmc_capabilities,
pmc_cpuinfo, pmc_ncpu,
pmc_npmc, pmc_pmcinfo,
pmc_width —
retrieve information about performance
monitoring counters
LIBRARY
library “libpmc”
SYNOPSIS
#include
<pmc.h>
int
pmc_capabilities(pmc_id_t
pmc, uint32_t
*caps);
int
pmc_cpuinfo(const
struct pmc_cpuinfo **cpu_info);
int
pmc_ncpu(void);
int
pmc_npmc(int
cpu);
int
pmc_pmcinfo(int
cpu, struct pmc_pmcinfo
**pmc_info);
int
pmc_width(pmc_id_t
pmc, uint32_t
*width);
DESCRIPTION
These functions retrieve information about performance monitoring hardware.Function
pmc_capabilities()
retrieves the hardware capabilities of a PMC. Argument
pmc is a PMC handle obtained by a prior call to
pmc_allocate().
The function sets argument caps to a bit mask of
capabilities supported by the PMC denoted by argument
pmc. PMC capabilities are described in
pmc(3).
Function
pmc_cpuinfo()
retrieves information about the CPUs in the system. Argument
cpu_info will be set to point to an internal structure
with information about the system's CPUs. The caller should not free this
pointer value. This structure has the following fields:
- pm_cputype
- Specifies the CPU type.
- pm_ncpu
- Specifies the number of CPUs in the system.
- pm_npmc
- Specifies the number of PMC rows per CPU.
- pm_nclass
- Specifies the number of distinct classes of PMCs in the system.
- pm_classes
- Contains an array of struct pmc_classinfo descriptors describing the properties of each class of PMCs in the system.
Function
pmc_ncpu()
is a convenience function that returns the maximum CPU number in the system.
On systems that support sparsely numbered CPUs, not all CPUs may be
physically present. Applications need to be prepared to deal with
nonexistent CPUs.
Function
pmc_npmc()
is a convenience function that returns the number of PMCs available in the
CPU specified by argument cpu.
Function
pmc_pmcinfo()
returns information about the current state of the PMC hardware in the CPU
specified by argument cpu. The location specified by
argument pmc_info is set to point an array of
struct pmc_info structures each describing the state
of one PMC in the CPU. These structure contain the following fields:
- pm_name
- A human readable name for the PMC.
- pm_class
- The PMC class for the PMC.
- pm_enabled
- Non-zero if the PMC is enabled.
- pm_rowdisp
- The disposition of the PMC row for this PMC. Row dispositions are documented in hwpmc(4).
- pm_ownerpid
- If the hardware is in use, the process id of the owner of the PMC.
- pm_mode
- The PMC mode as described in pmc(3).
- pm_event
- If the hardware is in use, the PMC event being measured.
- pm_flags
- If the hardware is in use, the flags associated with the PMC.
- pm_reloadcount
- For sampling PMCs, the reload count associated with the PMC.
Function
pmc_width()
is used to retrieve the width in bits of the hardware counters associated
with a PMC. Argument pmc is a PMC handle obtained by a
prior call to
pmc_allocate().
The function sets the location pointed to by argument
width to the width of the physical counters associated
with PMC pmc.
RETURN VALUES
Functions pmc_ncpu() and
pmc_npmc() returns a positive integer if successful;
otherwise the value -1 is returned and the global variable
errno is set to indicate the error.
Functions pmc_capabilities(),
pmc_cpuinfo(), pmc_pmcinfo()
and pmc_width() return 0 if successful; otherwise
the value -1 is returned and the global variable errno
is set to indicate the error.
ERRORS
A call to function pmc_capabilities() may
fail with the following errors:
- [
EINVAL] - The argument to the function was invalid.
Calls to functions pmc_cpuinfo(),
pmc_ncpu() and pmc_npmc()
may fail with the following errors:
- [
ENXIO] - A prior call to
pmc_init() to initialize the PMC library had failed.
A call to function pmc_pmcinfo() may fail
with the following errors:
- [
EINVAL] - The argument cpu was invalid.
- [
ENXIO] - The argument cpu specified a disabled or absent CPU.
A call to function pmc_width() may fail
with the following errors:
- [
EINVAL] - The argument to the function was invalid.
SEE ALSO
pmc(3), pmc_allocate(3), pmc_get_driver_stats(3), pmc_name_of_capability(3), pmc_name_of_class(3), pmc_name_of_cputype(3), pmc_name_of_event(3), pmc_name_of_mode(3), hwpmc(4)