pmc_control(2) - NetBSD Manual Pages

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PMC_CONTROL(2)            NetBSD System Calls Manual            PMC_CONTROL(2)


NAME

     pmc_control, pmc_get_info -- Hardware Performance Monitoring Interface


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <sys/pmc.h>

     int
     pmc_control(int ctr, int op, void *argp);

     int
     pmc_get_info(int ctr, int op, void *argp);


DESCRIPTION

     pmc_get_info() returns the number of counters in the system or informa-
     tion on a specified counter ctr.  The possible values for op are:

     PMC_INFO_NCOUNTERS
            When querying the number of counters in the system, ctr is ignored
            and argp is of type int *.  Upon return, the integer pointed to by
            argp will contain the number of counters that are available in the
            system.

     PMC_INFO_CPUCTR_TYPE
            When querying the type of a counter in the system, ctr refers to
            the counter being queried, and argp is of type int *.  Upon
            return, the integer pointed to by argp will contain the implemen-
            tation-dependent type of the specified counter.

            If ctr is -1, the integer pointed to by argp will contain the
            machine-dependent type describing the CPU or counter configura-
            tion.

     PMC_INFO_COUNTER_VALUE
            When querying the value of a counter in the system, ctr refers to
            the counter being queried, and argp is of type uint64_t *.  Upon
            return, the 64-bit integer pointed to by argp will contain the
            value of the specified counter.

     PMC_INFO_ACCUMULATED_COUNTER_VALUE
            When querying the value of a counter in the system, ctr refers to
            the counter being queried, and argp is of type uint64_t *.  Upon
            return, the 64-bit integer pointed to by argp will contain the sum
            of the accumulated values of specified counter in all exited sub-
            processes of the current process.

     pmc_control() manipulates the specified counter ctr in one of several
     fashions.  The op parameter determines the action taken by the kernel and
     also the interpretation of the argp parameter.  The possible values for
     op are:

     PMC_OP_START
            Starts the specified ctr running.  It must be preceded by a call
            with PMC_OP_CONFIGURE.  argp is ignored in this case and may be
            NULL.

     PMC_OP_STOP
            Stops the specified ctr from running.  argp is ignored in this
            case and may be NULL.

     PMC_OP_CONFIGURE
            Configures the specified ctr prior to running.  argp is a pointer
            to a struct pmc_counter_cfg.

                    struct pmc_counter_cfg {
                            pmc_evid_t      event_id;
                            pmc_ctr_t       reset_value;
                            uint32_t        flags;
                    };

            event_id
                   is the event ID to be counted.

            reset_value
                   is a value to which the counter should be reset on overflow
                   (if supported by the implementation).  This is most useful
                   when profiling (see PMC_OP_PROFSTART, below).  This value
                   is defined to be the number of counter ticks before the
                   next overflow.  So, to get a profiling tick on every hun-
                   dredth data cache miss, set the event_id to the proper
                   value for ``dcache-miss'' and set reset_value to 100.

            flags  Currently unused.

     PMC_OP_PROFSTART
            Configures the specified ctr for use in profiling.  argp is a
            pointer to a struct pmc_counter_cfg as in PMC_OP_CONFIGURE, above.
            This request allocates a kernel counter, which will fail if any
            process is using the requested counter.  Not all implementations
            or counters may support this option.

     PMC_OP_PROFSTOP
            Stops the specified ctr from being used for profiling.  argp is
            ignored in this case and may be NULL.


RETURN VALUES

     A return value of 0 indicates that the call succeeded.  Otherwise, -1 is
     returned and the global variable errno is set to indicate the error.


ERRORS

     Among the possible error codes from pmc_control() and pmc_get_info() are

     [EFAULT]           The address specified for the argp is invalid.

     [ENXIO]            Specified counter is not yet configured.

     [EINPROGRESS]      PMC_OP_START was passed for a counter that is already
                        running.

     [EINVAL]           Specified counter was invalid.

     [EBUSY]            If the requested counter is already in use--either by
                        the current process or by the kernel.

     [ENODEV]           If and only if the specified counter event is not
                        valid for the specified counter when configuring a
                        counter or starting profiling.

     [ENOMEM]           If the kernel is unable to allocate memory.


SEE ALSO

     pmc(1), pmc(9)


HISTORY

     The pmc_control() and pmc_get_info() system calls appeared in NetBSD 2.0.

NetBSD 8.0                     October 27, 2005                     NetBSD 8.0