man.bsd.lv manual page server

DESCRIPTION

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, data + 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().

void *parser;			/* cookie */
struct pmclog_ev ev;		/* parsed event */
int fd;				/* file descriptor */

fd = open(filename, O_RDONLY);	/* open log file */
parser = pmclog_open(fd);	/* initialize parser */
if (parser == NULL)
	--handle an out of memory error--;

/* read and parse data */
while (pmclog_read(parser, &ev) == 0) {
	assert(ev.pl_state == PMCLOG_OK);
	/* process the event */
	switch (ev.pl_type) {
	case PMCLOG_TYPE_ALLOCATE:
		--process a pmc allocation record--
		break;
	case PMCLOG_TYPE_PROCCSW:
		--process a thread context switch record--
		break;
	case PMCLOG_TYPE_CALLCHAIN:
		--process a callchain sample--
		break;
	--and so on--
	}
}

/* examine parser state */
switch (ev.pl_state) {
case PMCLOG_EOF:
	--normal termination--
	break;
case PMCLOG_ERROR:
	--look at errno here--
	break;
case PMCLOG_REQUIRE_DATA:
	--arrange for more data to be available for parsing--
	break;
default:
	assert(0);
	/*NOTREACHED*/
}

pmclog_close(parser);		/* cleanup */