PMCLOG(3) BSD Library Functions Manual PMCLOG(3)
NAME
pmclog_open, pmclog_close, pmclog_read, pmclog_feed -- parse event log data generated by hwpmc(4)
LIBRARY
Performance Counters Library (libpmc, -lpmc)
SYNOPSIS
#include <pmclog.h>
void *
pmclog_open(int fd);
void
pmclog_close(void *cookie);
int
pmclog_read(void *cookie, struct pmclog_ev *ev);
int
pmclog_feed(void *cookie, char *data, int len);
DESCRIPTION
These functions provide a way for application programs to extract events from an event stream generated by hwpmc(4).
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_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_pcsample pl_s;
struct pmclog_ev_pmcallocate pl_a;
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. Argu-
ment 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().
RETURN VALUES
Function pmclog_open() will return a non-NULL value if successful or NULL otherwise.
Function pmclog_read() will return 0 in case a complete event record was successfully read, or will return -1 and will set the pl_state field
of the event record to the appropriate code in case of an error.
Function pmclog_feed() will return 0 on success or -1 in case of failure.
EXAMPLES
A template for using the log file parsing API is shown below in pseudocode:
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_PCSAMPLE:
--process a PC 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 */
ERRORS
A call to pmclog_init_parser() may fail with any of the errors returned by malloc(3).
A call to pmclog_read() for a file based parser may fail with any of the errors returned by read(2).
SEE ALSO
read(2), malloc(3), pmc(3), hwpmc(4), pmcstat(8)
HISTORY
The pmclog API currently under development. It first appeared in FreeBSD 6.0.
BSD
March 26, 2006 BSD