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NAME | C SYNOPSIS | FORTRAN SYNOPSIS | JAVA SYNOPSIS | DESCRIPTION | NOTES | CAVEAT | DIAGNOSTICS | FILES | ENVIRONMENT | PCP ENVIRONMENT | SEE ALSO | COLOPHON |
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PMTRACE(3) Library Functions Manual PMTRACE(3)
pmtracebegin, pmtraceend, pmtraceabort, pmtracepoint, pmtraceobs,
pmtracecounter, pmtracestate, pmtraceerrstr - application-level
performance instrumentation services
#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
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
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);
The pcp_trace library functions provide a mechanism for identify‐
ing 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 par‐
ticular 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 aris‐
es 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 identi‐
fiers 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 rela‐
tively 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 up‐
date the statistics which the PMDA currently associates with the
given tag.
A second form of program instrumentation can be obtained from pm‐
tracepoint. 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 transac‐
tion. This function is most useful when start and end points are
not well defined. Examples of this would be when the code branch‐
es 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 be‐
tween 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 diag‐
nostic messages on the standard output stream at important pro‐
cessing points. The default protocol used between the trace PMDA
and individual pcp_trace client applications is a synchronous pro‐
tocol, which allows for dropped connections to be reestablished at
a later stage should this become possible. An asynchronous proto‐
col is also available which does not provide the reconnection ca‐
pability, 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 - ex‐
amples of the use of these flags in each supported language are
given in the demo applications (refer to the ``FILES'' section be‐
low).
┌─────────────┬───────────────────────────────────────────────┐
│ 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 stat‐
ic 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 New‐
StringUTF.
The pcp_trace Java class interface has been developed and verified
using version 1.1 of the Java Native Interface (JNI) specifica‐
tion.
Applications that use gethostbyname(3) should exercise caution be‐
cause the static fields in struct hostent may not be preserved
across some pcp_trace calls. In particular, pmtracebegin, pm‐
traceend, pmtracepoint, pmtracecounter, and pmtraceobs may all
call gethostbyname(3) internally.
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.
$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.
The pcp_trace routines communicate with the trace PMDA via a sock‐
et 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 re‐
mote 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 use‐
ful in cases where the remote host is at the end of a slow net‐
work, requiring longer latencies to establish the connection cor‐
rectly.
Environment variables with the prefix PCP_ are used to parameter‐
ize the file and directory names used by PCP. On each installa‐
tion, the file /etc/pcp.conf contains the local values for these
variables. The $PCP_CONF variable may be used to specify an al‐
ternative configuration file, as described in pcp.conf(5). Values
for these variables may be obtained programmatically using the
pmGetConfig(3) function.
file:$PCP_DOC_DIR/Tutorial/trace.html, pcp.man.tutorial, Provided
the, make(1), pmcd(1), pmdatrace(1), pmprobe(1), pmtrace(1), Rele‐
vant information is also available from the on-line PCP Tutorial.
This page is part of the PCP (Performance Co-Pilot) project. In‐
formation 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@groups.io. This page was obtained from the project's upstream
Git repository ⟨https://github.com/performancecopilot/pcp.git⟩ on
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-08-11.) 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 PMTRACE(3)
Pages that refer to this page: pmdatrace(1), pmtrace(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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