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perfmon (4)
>> perfmon (4) ( FreeBSD man: Специальные файлы /dev/* )
BSD mandoc
NAME
perfmon
- CPU performance-monitoring interface
SYNOPSIS
cpu I586_CPUcpu I686_CPUoptions PERFMON
DESCRIPTION
The
driver provides access to the internal performance-monitoring
capabilities of the
IntelPentium
and
Pentium Pro
CPUs.
These processors implement two internal counters which can be
configured to measure a variety of events for either count or duration
(in CPU cycles), as well as a cycle counter which counts clock cycles.
The
driver provides a device-style interface to these capabilities.
All access to the performance-monitoring counters is performed through
the special device file
``/dev/perfmon
''
This device supports a number of
ioctl(2)
requests, defined in
#include <machine/perfmon.h>
along with the definitions of the various counters for both
Pentium
and
Pentium Pro
processors.
NOTA BENE
The set of available events differs from processor to processor.
It
is the responsibility of the programmer to ensure that the event
numbers used are the correct ones for the CPU type being measured.
(struct pmc
)
Set up a counter with parameters and flags defined in the structure.
The following fields are defined in
struct pmc
int pmc_num
the number of the counter in question; must be less than
NPMC
(currently 2).
u_char pmc_event
the particular event number to be monitored, as defined in
In machine/perfmon.h .
u_char pmc_unit
the unit mask value, specific to the event type (see the
Intel
documentation).
u_char pmc_flags
flags modifying the operation of the counter (see below).
u_char pmc_mask
the counter mask value; essentially, this is a threshold used to
restrict the count to events lasting more (or less) than the specified
number of clocks.
The following
pmc_flags
values are defined:
PMCF_USR
count events in user mode
PMCF_OS
count events in kernel mode
PMCF_E
count number of events rather than their duration
PMCF_INV
invert the sense of the counter mask comparison
PMIOGET
(struct pmc
)
returns the current configuration of the specified counter.
PMIOSTART
PMIOSTOP
(int
)
starts (stops) the specified counter.
Due to hardware deficiencies,
counters must be started and stopped in numerical order.
(That is to
say, counter 0 can never be stopped without first stopping counter 1.)
The driver will
not
enforce this restriction (since it may not be present in future CPUs).
PMIORESET
(int
)
reset the specified counter to zero.
The counter should be stopped
with
PMIOSTOP
before it is reset.
All counters are automatically reset by
PMIOSETUP
PMIOREAD
(struct pmc_data
)
get the current value of the counter.
The
pmc_data
structure defines two fields:
int pmcd_num
the number of the counter to read
quad_t pmcd_value
the resulting value as a 64-bit signed integer
In the future, it may be possible to use the
RDPMC
instruction on
Pentium Pro
processors to read the counters directly.
PMIOTSTAMP
(struct pmc_tstamp
)
read the time stamp counter.
The
pmc_tstamp
structure defines two fields:
int pmct_rate
the approximate rate of the counter, in MHz
quad_t pmct_value
the current value of the counter as a 64-bit integer
It is important to note that the counter rate, as provided in the
pmct_rate
field, is often incorrect because of calibration difficulties and
non-integral clock rates.
This field should be considered more of a
hint or sanity-check than an actual representation of the rate of
clock ticks.
FILES
/dev/perfmon
character device interface to counters
/usr/include/machine/perfmon.h
include file with definitions of structures and event types
/usr/share/examples/perfmon
sample source code demonstrating use of all the
ioctl ();
commands
