GSP
Quick Navigator

Search Site

Linux VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Support
Contact Us
Online Help
Handbooks
Domain Status
Man Pages

FAQ
Virtual Servers
Pricing
Billing
Technical

Network
Facilities
Connectivity
Topology Map

Miscellaneous
Server Agreement
Year 2038
Credits
 

USA Flag

 

 

Man Pages


Manual Reference Pages  - PMCLOG (3)

NAME

pmclog_open, pmclog_close, pmclog_read, pmclog_feed - parse event log data generated by hwpmc(4)

CONTENTS

Library
Synopsis
Description
Return Values
Examples
Errors
See Also
History

LIBRARY


.Lb libpmc

SYNOPSIS


.In 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_allocate   pl_a;
                struct pmclog_ev_proccsw    pl_c;
                struct pmclog_ev_dropnotify pl_d;
                struct pmclog_ev_procexit   pl_e;
                struct pmclog_ev_initialize pl_i;
                struct pmclog_ev_pcsample   pl_s;
                struct pmclog_ev_pmcattach  pl_t;
                struct pmclog_ev_userdata   pl_u;
                struct pmclog_ev_procexec   pl_x;
       } 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_MAPPINGCHANGE
  A record describing an address space change for a process.
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.

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(3) API
.Ud It first appeared in
.Fx 6.0 .
Search for    or go to Top of page |  Section 3 |  Main Index


June 1, 2005 PMCLOG (3)

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.