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pmclog_read (3)

>> pmclog_read (3) ( FreeBSD man: Библиотечные вызовы )

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NAME

pmclog_open

 
pmclog_close

 
pmclog_read

 
pmclog_feed

 - parse event log data generated by

hwpmc(4)

LIBRARY

Lb libpmc

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 Fa 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 Fa cookie . Argument Fa 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 Fa *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 Fa *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 _exit2.
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 Fa data points to the start of a memory buffer containing fresh event data. Argument Fa len indicates the number of data bytes available. The memory range Bq Fa 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 (.);

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 */