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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
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.
The pcp_trace Java class interface has been developed and
verified using version 1.1 of the Java Native Interface (JNI)
specification.
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.
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
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.
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 $PCP_CONF variable may be used to
specify an alternative configuration file, as described in
pcp.conf(5). Values for these variables may be obtained
programmatically using the pmGetConfig(3) function.
file:$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.
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@groups.io. This page was obtained from the
project's upstream Git repository
⟨https://github.com/performancecopilot/pcp.git⟩ on 2024-06-14.
(At that time, the date of the most recent commit that was found
in the repository was 2024-06-14.) 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 2024-06-26 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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