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NAME | C SYNOPSIS | DESCRIPTION | EXAMPLE | SEE ALSO | COLOPHON |
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PMDAEVENTARRAY(3) Library Functions Manual PMDAEVENTARRAY(3)
pmdaEventNewArray, pmdaEventResetArray, pmdaEventReleaseArray,
pmdaEventAddRecord, pmdaEventAddMissedRecord, pmdaEventAddParam,
pmdaEventGetAddr, pmdaEventNewHighResArray,
pmdaEventResetHighResArray, pmdaEventReleaseHighResArray,
pmdaEventAddHighResRecord, pmdaEventAddHighResMissedRecord,
pmdaEventAddHighResParam, pmdaEventGetHighResAddr,
pmdaEventHighResAddParam, pmdaEventHighResGetAddr - utilities for
PMDAs to build packed arrays of event records
#include <pcp/pmapi.h>
#include <pcp/pmda.h>
int pmdaEventNewArray(void);
int pmdaEventResetArray(int idx);
int pmdaEventReleaseArray(int idx);
int pmdaEventAddRecord(int idx, struct timeval *tp, int flags);
int pmdaEventAddMissedRecord(int idx, struct timeval *tp,
int nmissed);
int pmdaEventAddParam(int idx, pmID pmid, int type,
pmAtomValue *avp);
pmEventArray *pmdaEventGetAddr(int idx);
int pmdaEventNewHighResArray(void);
int pmdaEventResetHighResArray(int idx);
int pmdaEventReleaseHighResArray(int idx);
int pmdaEventAddHighResRecord(int idx, struct timespec *ts,
int flags);
int pmdaEventAddHighResMissedRecord(int idx, struct timespec *ts,
int nmissed);
int pmdaEventAddHighResParam(int idx, pmID pmid, int type,
pmAtomValue *avp);
pmHighResEventArray *pmdaEventGetHighResAddr(int idx);
cc ... -lpcp
A Performance Metrics Domain Agent (PMDA) that wishes to export
event records (or trace records) is encouraged to use a metric of
either type PM_TYPE_EVENT or PM_TYPE_HIGHRES_EVENT to encode a
group of event records into a single packed array.
The only difference between the two metric types is the resolution
of the timestamp associated with each - in high resolution form it
is nanosecond scale (see clock_gettime(2)), otherwise it is mi‐
croseconds (see gettimeofday(2)). For simplicity, we will only
refer to the lower resolution API and data structures hereafter -
however, the higher resolution variants are all named similarly
and are used in the same way.
The packed array of event records format is defined in
<pcp/pmapi.h> and consists of a pmEventArray structure containing
a variable number of pmEventRecord structures, each of which con‐
tains a variable number of pmEventParameter structures, which in
turn may contain a variable length value for each parameter of
each event record.
The higher resolution equivalents are defined in the same loca‐
tion, and the structures are named the same. Note that the
pmEventParameter structure has no timestamp associated with it,
hence it this does not have a high resolution counterpart.
The routines described here are designed to assist the PMDA devel‐
oper in building a packed array of event records, and managing all
of the memory allocations required to hold each instance of an ar‐
ray of event records in a contiguous buffer. Normal use would be
as part of PMDA's pmdaFetchCallBack method.
pmdaEventNewArray is used to create a new event array. The return
value is a small integer that is used as the idx parameter to the
other routines to identify a specific event array. If needed, a
PMDA can create and use multiple event arrays.
To start a new cycle and refill an event array from the beginning,
call pmdaEventResetArray.
If the PMDA has finished with an event array, pmdaEventReleaseAr‐
ray may be used to release the underlying storage and ``close''
the event array so that subsequent attempts to use idx will return
PM_ERR_NOCONTEXT.
To start a new event record, use pmdaEventAddRecord. The time‐
stamp for the event record is given via tp and the flags parameter
may be used to set the control field that determines the type of
the event record - flags may be the bit-wise ``or'' of one or more
of the PM_EVENT_FLAG_* values defined in <pcp/pmapi.h> (but note
that PM_EVENT_FLAG_MISSED should not be used in this context).
If event records have been missed, either because the PMDA cannot
keep up or because the PMAPI client cannot keep up, then pmdaEven‐
tAddMissedRecord may be used. idx and tp have the same meaning as
for pmdaEventAddRecord and nmissed is the number of event records
that have been missed at this point in the time-series of event
records. pmdaEventAddMissedRecord may be called multiple times
for a single batch of event records if there are more than one
``missed event record'' episode.
Once an event record has been started by calling pmdaEventAd‐
dRecord, one or more event parameters may be added using pmdaEven‐
tAddParam. The pmid and type parameters describe the PMID of the
parameter and the data type (one of the PM_TYPE_* values from
<pcp/pmapi.h>) of the value that is passed via avp. type should
one where the size of the value is implied by the type or by the
length of a string value (for PM_TYPE_STRING) or encoded within
avp->vbp (for PM_TYPE_AGGREGATE).
Once the packed array has been constructed, pmdaEventGetAddr
should be used to initialize the ea_type and ea_len fields at the
start of the pmEventArray and return the base address of the event
array that is assigned to the vp field of the pmAtomValue struc‐
ture that the pmdaFetchCallBack method should return.
pmdaEventHighResAddParam and pmdaEventHighResGetAddr are previous
names for pmdaEventAddHighResParam and pmdaEventGetHighResAddr
(respectively) that have been maintained for backwards compatibil‐
ity.
The following skeletal code shows how these routines might be
used.
int sts;
int myarray;
int first = 1;
pmEventArray eap;
if (first) {
first = 0;
if ((myarray = pmdaEventNewArray()) < 0) {
// report error and fail
}
}
pmdaEventResetArray(myarray);
// loop over all event records to be exported
... {
struct timeval stamp;
int flags;
// establish timestamp and set flags to 0 or some combination
// of PM_EVENT_FLAG_POINT, PM_EVENT_FLAG_START, PM_EVENT_FLAG_ID,
// etc
if ((sts = pmdaEventAddRecord(myarray, &stamp, flags)) < 0) {
// report error and fail
}
// loop over all parameters for this event record
... {
pmID pmid;
int type;
pmAtomValue atom;
// construct pmid, type and atom for the parameter and
// its value
if ((sts = pmdaEventAddParam(myarray, pmid, type, &atom)) < 0) {
// report error and fail
}
}
// if some event records were missed (could be at the start
// of the exported set, or at the end, or in the middle, or
// a combination of multiple missed record episodes)
... {
int nmissed;
struct timeval stamp;
if ((sts = pmdaEventAddMissedRecord(myarray, &stamp, nmissed)) < 0) {
// report error and fail
}
}
}
// finish up
eap = pmdaEventGetAddr(myarray);
clock_gettime(2), gettimeofday(2), pmdaEventNewQueue(3),
pmdaEventNewClient(3), PMDA(3) and pmEventFlagsStr(3).
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
2025-02-02. (At that time, the date of the most recent commit
that was found in the repository was 2025-01-30.) 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 PMDAEVENTARRAY(3)
Pages that refer to this page: pmdaeventclient(3), pmdaeventqueue(3), pmeventflagsstr(3), LOGARCHIVE(5)
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HTML rendering created 2025-02-02 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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