NAME | C SYNOPSIS | FORTRAN SYNOPSIS | JAVA SYNOPSIS | DESCRIPTION | ENVIRONMENT | NOTES | FILES | PCP ENVIRONMENT | SEE ALSO | DIAGNOSTICS | CAVEAT | COLOPHON

PMDATRACE(3)              Library Functions Manual              PMDATRACE(3)

NAME         top

       pmtracebegin,  pmtraceend,  pmtraceabort,  pmtracepoint,  pmtraceobs,
       pmtracecounter, pmtracestate, pmtraceerrstr - application-level  per‐
       formance instrumentation services

C SYNOPSIS         top

       #include <pcp/trace.h>

       int pmtracebegin(const char *tag);
       int pmtraceend(const char *tag);
       int pmtraceabort(const char *tag);
       int pmtracepoint(const char *tag);
       int pmtraceobs(const char *tag, double value);
       int pmtracecounter(const char *tag, double value);
       char *pmtraceerrstr(int code);
       int pmtracestate(int flags);

       cc ... -lpcp_trace

FORTRAN SYNOPSIS         top

       character*(*) tag
       integer code
       integer flags
       integer state
       character*(*) estr
       real*8 value

       code = pmtracebegin(tag)
       code = pmtraceend(tag)
       code = pmtraceabort(tag)
       code = pmtracepoint(tag)
       code = pmtraceobs(tag, value)
       code = pmtracecounter(tag, value)
       pmtraceerrstr(code, estr)
       state = pmtracestate(flags)

       f77 ... -lpcp_trace  or  f90 ... -lpcp_trace

JAVA SYNOPSIS         top

       import sgi.pcp.trace;

       int trace.pmtracebegin(String tag);
       int trace.pmtraceend(String tag);
       int trace.pmtraceabort(String tag);
       int trace.pmtracepoint(String tag);
       int trace.pmtraceobs(String tag, double value);
       int trace.pmtracecounter(String tag, double value);
       String trace.pmtraceerrstr(int code);
       int trace.pmtracestate(int flags);

DESCRIPTION         top

       The pcp_trace library functions provide a mechanism for identifying
       sections of a program as transactions or events for use by the trace
       Performance Metrics Domain Agent (refer to pmdatrace(1) and PMDA(3)).

       The monitoring of transactions using the Performance Co-Pilot (PCP)
       infrastructure is initiated through a call to pmtracebegin.  Time
       will be recorded from the end of each pmtracebegin call to the start
       of the following call to pmtraceend, where the same tag identifier is
       used in both calls.  Following from this, no visible recording will
       occur until at least one call to pmtraceend is made referencing a tag
       previously used in a call to pmtracebegin.

       A transaction which is currently in progress can be cancelled by
       calling pmtraceabort.  No transaction data gathered for that
       particular transaction will be exported, although data from previous
       and subsequent successful transactions with that tag name are still
       exported.  This is most useful when an error condition arises during
       transaction processing and the transaction does not run to
       completion.

       The tag argument to pmtracebegin, pmtraceend and pmtraceabort is used
       to uniquely identify each transaction within the pcp_trace library
       and later by the trace PMDA as the instance domain identifiers for
       the transaction performance metrics which it exports.  These routines
       are most useful when used around blocks of code which are likely to
       be executed a number of times over some relatively long time period
       (in a daemon process, for example).

       pmtracebegin has two distinct roles - firstly as the initiator of a
       new transaction, and secondly as a mechanism for setting a new start
       time.  Similarly, pmtraceend is used to register a new tag and its
       initial state with the trace PMDA, or alternatively to update the
       statistics which the PMDA currently associates with the given tag.

       A second form of program instrumentation can be obtained from
       pmtracepoint.  This is a simpler form of monitoring as it exports
       only the number of times that a particular point in a program has
       been passed.  This differs to the transaction monitoring offered by
       pmtracebegin and pmtraceend, which exports a running count of
       successful transaction completions as well as statistics on the time
       interval between the start and end points of each transaction.  This
       function is most useful when start and end points are not well
       defined.  Examples of this would be when the code branches in such a
       way that a transaction cannot be clearly identified, or when
       processing does not follow a transactional model, or the desired
       instrumentation is akin to event rates rather than event service
       times.

       The pmtraceobs and pmtracecounter functions have similar semantics to
       pmtracepoint, but also allow an arbitrary numeric value to be passed
       to the trace PMDA.  The most recent value for each tag is then
       immediately available from the PMDA.  The only difference between
       pmtraceobs and pmtracecounter is that the value exported via
       pmtracecounter is assumed to be a monotonically increasing counter
       value (e.g. the number of bytes read from a socket), whereas the
       value exported via pmtraceobs can be any value at all.

       pmtracestate allows the application to set state flags which are
       honoured by subsequent calls to the pcp_trace library routines.
       There are currently two types of flag - debugging flags and the
       asynchronous protocol flag.  A single call may specify a number of
       flags together, combined using a (bitwise) logical OR operation, and
       overrides the previous state setting.

       The debugging flags to pmtracestate cause pcp_trace to print
       diagnostic messages on the standard output stream at important
       processing points.  The default protocol used between the trace PMDA
       and individual pcp_trace client applications is a synchronous
       protocol, which allows for dropped connections to be reestablished at
       a later stage should this become possible.  An asynchronous protocol
       is also available which does not provide the reconnection capability,
       but which does away with much of the overhead inherent in synchronous
       communication.  This behaviour can be toggled using the pmtracestate
       call, but must be called before other calls to the library.  This
       differs to the debugging state behaviour, which can be altered at any
       time.  pmtracestate returns the previous state (setting prior to
       being called).

       The following table describes each of the pmtracestate flags -
       examples of the use of these flags in each supported language are
       given in the demo applications (refer to the ``FILES'' section
       below).

           ┌────────────┬───────────────────────────────────────────────┐
           │State Flags │                   Semantics                   │
           ├────────────┼───────────────────────────────────────────────┤
           │0  NONE     │ Synchronous PDUs and no diagnostics (default) │
           │1  API      │ Shows processing just below the API (debug)   │
           │2  COMMS    │ Shows network-related activity (debug)        │
           │4  PDU      │ Shows app<->PMDA IPC traffic (debug)          │
           │8  PDUBUF   │ Shows internal IPC buffer management (debug)  │
           │16 NOAGENT  │ No PMDA communications at all (debug)         │
           │32 ASYNC    │ Use the asynchronous PDU protocol (control)   │
           └────────────┴───────────────────────────────────────────────┘
       Should any of the pcp_trace library functions return a negative
       value, an error has occurred.  This can be diagnosed further using
       the pmtraceerrstr routine, which takes the negative return value as
       its code argument, and in the C-callable interface returns a pointer
       to the associated error message.  This points into a static error
       table, and should therefore not be passed to free(3).  The Fortran-
       callable interface has a slightly different syntax, requiring the
       destination character array to be passed in as the second argument.
       The Java-callable interface returns a UTF-8 string, created using the
       JNI (Java Native Interface) routine NewStringUTF.

ENVIRONMENT         top

       The pcp_trace routines communicate with the trace PMDA via a socket
       connection, which by default uses TCP/IP port number 4323.  This can
       be over-ridden by setting PCP_TRACE_PORT to a different port number
       when the application is started.  The host where the trace PMDA is
       running is by default the localhost, but this can be changed using
       PCP_TRACE_HOST.  When attempting to connect to a remote trace PMDA,
       after some specified time interval has elapsed, the connection
       attempt will be aborted and an error status will be returned.  The
       default timeout interval is 3 seconds, and this can be modified by
       setting PCP_TRACE_TIMEOUT in the environment to a real number of
       seconds for the desired timeout.  This is most useful in cases where
       the remote host is at the end of a slow network, requiring longer
       latencies to establish the connection correctly.

NOTES         top

       The pcp_trace Java class interface has been developed and verified
       using version 1.1 of the Java Native Interface (JNI) specification.

FILES         top

       $PCP_DEMOS_DIR/trace/*.c
                 Sample C programs and source for pmtrace(1).  Use make(1)
                 to build these programs.

       $PCP_DEMOS_DIR/trace/fapp1.f
                 Sample Fortran program.  Call `make fortran77' or `make
                 fortran90' to build this program.

       $PCP_DEMOS_DIR/trace/japp1.java
                 Sample Java program.  `make java' builds the java class
                 file.

       /usr/java/classes/sgi/pcp/trace.java
                 Java trace class definition.

PCP ENVIRONMENT         top

       Environment variables with the prefix PCP_ are used to parameterize
       the file and directory names used by PCP.  On each installation, the
       file /etc/pcp.conf contains the local values for these variables.
       The $PCP_CONF variable may be used to specify an alternative
       configuration file, as described in pcp.conf(5).  Values for these
       variables may be obtained programmatically using the pmGetConfig(3)
       function.

SEE ALSO         top

       file:$PCP_DOC_DIR/Tutorial/trace.html, pcp.man.tutorial, Provided
       the, make(1), pmcd(1), pmdatrace(1), pmprobe(1), pmtrace(1), Relevant
       information is also available from the on-line PCP Tutorial,
       subsystem from the PCP images has been installed, access the URL and
       from your web browser.

DIAGNOSTICS         top

       A negative return value from a pcp_trace function indicates that an
       error has occurred - if this is the case, the return value can be
       passed to pmtraceerrstr to obtain the associated error message.

       Success is indicated by a return value of zero.

       pmtracestate also returns an integer representing the state flags
       which were set prior to the call.

CAVEAT         top

       Applications that use gethostbyname(3) should exercise caution
       because the static fields in struct hostent may not be preserved
       across some pcp_trace calls.  In particular, pmtracebegin,
       pmtraceend, pmtracepoint, pmtracecounter, and pmtraceobs may all call
       gethostbyname(3) internally.

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
       Information about the project can be found at ⟨http://www.pcp.io/⟩.
       If you have a bug report for this manual page, send it to
       pcp@oss.sgi.com.  This page was obtained from the project's upstream
       Git repository ⟨git://git.pcp.io/pcp⟩ on 2017-04-25.  If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page, or
       you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

Performance Co-Pilot                 PCP                        PMDATRACE(3)

Pages that refer to this page: pmdatrace(1)pmtrace(1)