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NAME | C SYNOPSIS | DESCRIPTION | EXAMPLES | LARGE DELTA VALUES | SEE ALSO | DIAGNOSTICS | COLOPHON |
PMSETMODE(3) Library Functions Manual PMSETMODE(3)
pmSetMode - set collection time parameters for the current PMAPI con‐
text
#include <pcp/pmapi.h>
int pmSetMode(int mode, const struct timeval *when, int delta);
cc ... -lpcp
pmSetMode is used to define the collection time and/or mode for
accessing performance metrics and meta-data in the current
Performance Metrics Application Programming Interface (PMAPI)
context. This mode affects the semantics of subsequent calls to the
following PMAPI routines: pmFetch(3), pmFetchArchive(3),
pmLookupDesc(3), pmGetInDom(3), pmLookupInDom(3) and pmNameInDom(3).
If mode is PM_MODE_LIVE then all information is returned from the
active pool of performance metrics as of the time that the PMAPI call
is made, and the other two parameters to pmSetMode are ignored.
PM_MODE_LIVE is the default mode when a new PMAPI context of type
PM_CONTEXT_HOST is created.
If the mode is not PM_MODE_LIVE, then the when parameter defines a
time origin, and all requests for meta-data (metric descriptions and
instance identifiers from the instance domains) will be processed to
reflect the state of the meta-data as of the time origin, i.e. we use
the last state of this information at, or before, the time origin.
If the mode is PM_MODE_INTERP then, in the case of pmFetch(3), the
underlying code will use an interpolation scheme to compute the
values of the metrics from the values recorded for times in the
proximity of the time origin. A mode of PM_MODE_INTERP may only be
used with an archive context.
If the mode is PM_MODE_FORW then, in the case of pmFetch(3), the
collection of recorded metric values will be scanned in a forwards
direction in time, until values for at least one of the requested
metrics is located after the time origin, and then all requested
metrics stored in the set of archives at that time will be returned
with the corresponding timestamp. A mode of PM_MODE_FORW may only be
used with an archive context.
If the mode is PM_MODE_BACK then, the situation is the same as for
PM_MODE_FORW, except a pmFetch(3) will be serviced by scanning the
collection of recorded metrics in a backwards direction in time for
metrics before the time origin. A mode of PM_MODE_BACK may only be
used with an archive context.
If the mode is PM_MODE_FORW or PM_MODE_BACK, and no qualifying
metrics can be found in the requested direction of searching before
the end or start of the set of archive logs is found, then pmFetch(3)
returns the special error indicator, PM_ERR_EOL.
For modes other than PM_MODE_LIVE, after each successful pmFetch(3),
the time origin is reset to the timestamp returned via the pmResult
structure from pmFetch(3).
The pmSetMode parameter delta defines an additional number of time
units that should be used to adjust the time origin (forwards or
backwards), after the new time origin from the pmResult has been
determined. This automatic adjustment of the time origin only occurs
when the mode is PM_MODE_INTERP, and the adjustment is applied, even
if the pmFetch(3) fails because the time origin is outside the range
defined by the records in a set of archive logs, i.e. returns
PM_ERR_EOL.
By default delta is interpreted as milliseconds (but see the LARGE
DELTA VALUES section below).
Using these mode options, an application can implement replay,
playback, fast forward, reverse, etc. for performance metric values
held in the set of archive logs by alternating calls to pmSetMode and
pmFetch(3).
As a special case, if when is NULL then the mode and delta arguments
are used as described above, but the current time in the archive is
not altered.
The following code fragment may be used to dump just those values
recorded in an archive in correct temporal sequence, for a selected
set of performance metrics; this uses the default collection time
mechanisms.
pmNewContext(PM_CONTEXT_ARCHIVE, "myarchive");
while (pmFetch(npmid, pmidlist, &result) != PM_ERR_EOL) {
/*
* process real metric values as of result->timestamp
*/
. . .
pmFreeResult(result);
}
Alternatively, to replay interpolated metrics from the log in reverse
chronological order, at 10 second intervals (of recorded time), the
following code fragment could be used.
struct timeval mytime;
mytime.tv_sec = 0x7fffffff; /* or use pmGetArchiveEnd(&mtime) */
pmSetMode(PM_MODE_BACK, &mytime, 0);
pmFetchArchive(&result);
mytime = result->timestamp;
pmFreeResult(result);
pmSetMode(PM_MODE_INTERP | PM_XTB_SET(PM_TIME_SEC), &mytime, -10);
while (pmFetch(numpmid, pmidlist, &result) != PM_ERR_EOL) {
/*
* process interpolated metric values as of
* result->timestamp
*/
. . .
pmFreeResult(result);
}
Because delta is an int and treated as milliseconds by default there
is a limit on the maximum absolute value of delta that can be
specified with this default interpretation, namely about 24 days if a
signed int has 31 bits of precision. To accommodate longer values of
delta the high-order bits of the mode parameter is also used to
optionally set the units of time for the delta parameter. To specify
the units of time use the PM_XTB_SET macro with one of the values
PM_TIME_NSEC, PM_TIME_MSEC, PM_TIME_SEC, etc. to set the mode as
follows:
PM_MODE_INTERP | PM_XTB_SET(PM_TIME_XXXX)
The following code shows how this could be done if the desired delta
is initially encoded in interval (a struct timeval).
struct timeval interval;
int mode;
mode = ...
if (abs(interval.tv_sec / (3600*24)) <= 24) {
/* default encoding of milliseconds is fine */
mode = PM_MODE_INTERP;
delta = interval.tv_sec * 1000 + (interval.tv_usec + 500)/ 1000;
}
else {
/* encode delta in units of seconds */
mode = PM_MODE_INTERP | PM_XTB_SET(PM_TIME_SEC);
delta = interval.tv_sec + (interval.tv_usec + 500000)/ 1000000;
}
For millisecond encoding of delta, using PM_XTB_SET(PM_TIME_MSEC) is
functionally equivalent to not using PM_XTB_SET at all.
PMAPI(3), pmFetch(3), pmFetchArchive(3), pmGetInDom(3),
pmLookupDesc(3), pmLookupInDom(3) and pmNameInDom(3).
PM_ERR_MODE
The mode parameter is invalid
This page is part of the PCP (Performance Co-Pilot) project.
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If you have a bug report for this manual page, send it to
pcp@oss.sgi.com. This page was obtained from the project's upstream
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COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
Performance Co-Pilot PCP PMSETMODE(3)
Pages that refer to this page: pcpintro(3), pmapi(3), pmfetch(3), pmfetcharchive(3), pmfetchgroup(3), pmgetarchiveend(3), pmnewcontext(3), pmstore(3), pmtime(3), QmcGroup(3)