pmdaeventarray(3) - Linux manual page (original) (raw)
PMDAEVENTARRAY(3) Library Functions Manual PMDAEVENTARRAY(3)
NAME top
**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 recordsC SYNOPSIS top
**#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**DESCRIPTION top
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)](../man2/clock%5Fgettime.2.html)), otherwise it is mi‐
croseconds (see [gettimeofday(2)](../man2/gettimeofday.2.html)). 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.EXAMPLE top
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);SEE ALSO top
[clock_gettime(2)](../man2/clock%5Fgettime.2.html), [gettimeofday(2)](../man2/gettimeofday.2.html), [pmdaEventNewQueue(3)](../man3/pmdaEventNewQueue.3.html),
[pmdaEventNewClient(3)](../man3/pmdaEventNewClient.3.html), [PMDA(3)](../man3/PMDA.3.html) and [pmEventFlagsStr(3)](../man3/pmEventFlagsStr.3.html).COLOPHON top
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Pages that refer to this page:pmdaeventclient(3), pmdaeventqueue(3), pmeventflagsstr(3), LOGARCHIVE(5)