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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 resolu‐
tion of the timestamp associated with each - in high resolution
form it is nanosecond scale (see clock_gettime(2)), otherwise it
is microseconds (see gettimeofday(2)). For simplicity, we will
only refer to the lower resolution API and data structures here‐
after - 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 de‐
veloper in building a packed array of event records, and managing
all of the memory allocations required to hold each instance of
an array 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 re‐
turn 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 begin‐
ning, 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 re‐
turn 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 parame‐
ter 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 con‐
text).
If event records have been missed, either because the PMDA cannot
keep up or because the PMAPI client cannot keep up, then pm‐
daEventAddMissedRecord 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-se‐
ries 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 pm‐
daEventAddParam. 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
structure that the pmdaFetchCallBack method should return.
pmdaEventHighResAddParam and pmdaEventHighResGetAddr are previous
names for pmdaEventAddHighResParam and pmdaEventGetHighResAddr
(respectively) that have been maintained for backwards compati‐
bility.
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 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 PMDAEVENTARRAY(3)
Pages that refer to this page: pmdaeventclient(3), pmdaeventqueue(3), pmeventflagsstr(3), LOGARCHIVE(5)
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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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