Manual Pages  — PMCLOG

A new event log parser is allocated using pmclog_open(). Argument fd may be a file descriptor opened for reading if the event stream is present in a file, or the constant PMCLOG_FD_NONE for an event stream present in memory. This function returns a cookie that is passed into the other functions in this API set.

Function pmclog_read() returns the next available event in the event stream associated with argument cookie. Argument ev points to an event descriptor that which will contain the result of a successfully parsed event.

An event descriptor returned by pmclog_read() has the following structure:

struct pmclog_ev {
       enum pmclog_state pl_state;      /* parser state after 'get_event()' */
       off_t             pl_offset;     /* byte offset in stream */
       size_t            pl_count;      /* count of records so far */
       struct timespec   pl_ts;         /* log entry timestamp */
       enum pmclog_type  pl_type;       /* log entry kind */
       union {                          /* log entry data */
                struct pmclog_ev_callchain   pl_cc;
                struct pmclog_ev_closelog    pl_cl;
                struct pmclog_ev_dropnotify  pl_d;
                struct pmclog_ev_initialize  pl_i;
                struct pmclog_ev_map_in      pl_mi;
                struct pmclog_ev_map_out     pl_mo;
                struct pmclog_ev_pmcallocate pl_a;
                struct pmclog_ev_pmcallocatedyn pl_ad;
                struct pmclog_ev_pmcattach   pl_t;
                struct pmclog_ev_pmcdetach   pl_d;
                struct pmclog_ev_proccsw     pl_c;
                struct pmclog_ev_procexec    pl_x;
                struct pmclog_ev_procexit    pl_e;
                struct pmclog_ev_procfork    pl_f;
                struct pmclog_ev_sysexit     pl_e;
                struct pmclog_ev_userdata    pl_u;
       } pl_u;
};

The current state of the parser is recorded in pl_state. This field can take on the following values:

PMCLOG_EOF	(For file based parsers only) An end-of-file condition was encountered on the configured file descriptor.
PMCLOG_ERROR	An error occurred during parsing.
PMCLOG_OK	A complete event record was read into *ev.
PMCLOG_REQUIRE_DATA
	There was insufficient data in the event stream to assemble a complete event record. For memory based parsers, more data can be fed to the parser using function pmclog_feed(). For file based parsers, function pmclog_read() may be retried when data is available on the configured file descriptor.

The rest of the event structure is valid only if field pl_state contains PMCLOG_OK. Field pl_offset contains the offset of the current record in the byte stream. Field pl_count contains the serial number of this event. Field pl_ts contains a timestamp with the system time when the event occurred. Field pl_type denotes the kind of the event returned in argument *ev and is one of the following:

PMCLOG_TYPE_CLOSELOG	A marker indicating a successful close of a log file. This record will be the last record of a log file.
PMCLOG_TYPE_DROPNOTIFY	A marker indicating that hwpmc(4) had to drop data due to a resource constraint.
PMCLOG_TYPE_INITIALIZE	An initialization record. This is the first record in a log file.
PMCLOG_TYPE_MAP_IN	A record describing the introduction of a mapping to an executable object by a kldload(2) or mmap(2) system call.
PMCLOG_TYPE_MAP_OUT	A record describing the removal of a mapping to an executable object by a kldunload(2) or munmap(2) system call.
PMCLOG_TYPE_PCSAMPLE	A record containing an instruction pointer sample.
PMCLOG_TYPE_PMCALLOCATE
	A record describing a PMC allocation operation.
PMCLOG_TYPE_PMCATTACH	A record describing a PMC attach operation.
PMCLOG_TYPE_PMCDETACH	A record describing a PMC detach operation.
PMCLOG_TYPE_PROCCSW	A record describing a PMC reading at the time of a process context switch.
PMCLOG_TYPE_PROCEXEC	A record describing an execve(2) by a target process.
PMCLOG_TYPE_PROCEXIT	A record describing the accumulated PMC reading for a process at the time of _exit(2).
PMCLOG_TYPE_PROCFORK	A record describing a fork(2) by a target process.
PMCLOG_TYPE_SYSEXIT	A record describing a process exit, sent to processes owning system-wide sampling PMCs.
PMCLOG_TYPE_USERDATA	A record containing user data.

Function pmclog_feed() is used with parsers configured to parse memory based event streams. It is intended to be called when function pmclog_read() indicates the need for more data by a returning PMCLOG_REQUIRE_DATA in field pl_state of its event structure argument. Argument data points to the start of a memory buffer containing fresh event data. Argument len indicates the number of data bytes available. The memory range [data, ,, Fa, data, No, +, Fa, len] must remain valid till the next time pmclog_read() returns an error. It is an error to use pmclog_feed() on a parser configured to parse file data.

Function pmclog_close() releases the internal state allocated by a prior call to pmclog_open().

A call to pmclog_read() for a file based parser may fail with any of the errors returned by read(2).