1PMSETMODE(3) Library Functions Manual PMSETMODE(3)
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6 pmSetMode, pmSetModeHighRes - set collection time parameters for the
7 current PMAPI context
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10 #include <pcp/pmapi.h>
11 int pmSetMode(int mode, const struct timeval *when, int delta);
13 int pmSetModeHighRes(int mode, const struct timespec *when, const struct timespec *delta);
14 cc ... -lpcp
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18 pmSetMode and pmSetModeHighRes are used to define the collection time
19 and/or mode for accessing performance metrics and meta-data in the cur‐
20 rent Performance Metrics Application Programming Interface (PMAPI) con‐
21 text. This mode affects the semantics of subsequent calls to the fol‐
22 lowing PMAPI routines: pmFetch(3), pmFetchArchive(3), pmLookupDesc(3),
23 pmGetInDom(3), pmLookupInDom(3) and pmNameInDom(3).
24 If mode is PM_MODE_LIVE then all information is returned from the ac‐
26 tive pool of performance metrics as of the time that the PMAPI call is
27 made, and the other two parameters to pmSetMode are ignored.
28 PM_MODE_LIVE is the default mode when a new PMAPI context of type
29 PM_CONTEXT_HOST is created.
30 If the mode is not PM_MODE_LIVE, then the when parameter defines a time
32 origin, and all requests for meta-data (metric descriptions and in‐
33 stance identifiers from the instance domains) will be processed to re‐
34 flect the state of the meta-data as of the time origin, i.e. we use the
35 last state of this information at, or before, the time origin.
36 If the mode is PM_MODE_INTERP then, in the case of pmFetch(3), the un‐
38 derlying code will use an interpolation scheme to compute the values of
39 the metrics from the values recorded for times in the proximity of the
40 time origin. A mode of PM_MODE_INTERP may only be used with an archive
41 context.
42 If the mode is PM_MODE_FORW then, in the case of pmFetch(3), the col‐
44 lection of recorded metric values will be scanned in a forwards direc‐
45 tion in time, until values for at least one of the requested metrics is
46 located after the time origin, and then all requested metrics stored in
47 the set of archives at that time will be returned with the correspond‐
48 ing timestamp. A mode of PM_MODE_FORW may only be used with an archive
49 context.
50 If the mode is PM_MODE_BACK then, the situation is the same as for
52 PM_MODE_FORW, except a pmFetch(3) will be serviced by scanning the col‐
53 lection of recorded metrics in a backwards direction in time for met‐
54 rics before the time origin. A mode of PM_MODE_BACK may only be used
55 with an archive context.
56 If the mode is PM_MODE_FORW or PM_MODE_BACK, and no qualifying metrics
58 can be found in the requested direction of searching before the end or
59 start of the set of archives is found, then pmFetch(3) returns the spe‐
60 cial error indicator, PM_ERR_EOL.
61 For modes other than PM_MODE_LIVE, after each successful pmFetch(3),
63 the time origin is reset to the timestamp returned via the pmResult
64 structure from pmFetch(3).
65 The pmSetMode parameter delta defines an additional number of time
67 units that should be used to adjust the time origin (forwards or back‐
68 wards), after the new time origin from the pmResult has been deter‐
69 mined. This automatic adjustment of the time origin only occurs when
70 the mode is PM_MODE_INTERP, and the adjustment is applied, even if the
71 pmFetch(3) fails because the time origin is outside the range defined
72 by the records in a set of archives, i.e. returns PM_ERR_EOL.
73 By default the delta parameter of pmSetMode is interpreted as millisec‐
75 onds (but see the LARGE DELTA VALUES section below).
76 In the pmSetModeHighRes variant of this interface, the delta parameter
78 is a struct timespec so can directly represent any interval.
79 Using these mode options, an application can implement replay, play‐
81 back, fast forward, reverse, etc. for performance metric values held in
82 the set of archives by alternating calls to pmSetMode and pmFetch(3).
83 As a special case, if when is NULL then the mode and delta arguments
85 are used as described above, but the current time in the archive is not
86 altered.
87
89 The following code fragment may be used to dump just those values
90 recorded in an archive in correct temporal sequence, for a selected set
91 of performance metrics; this uses the default collection time mecha‐
92 nisms.
93 pmNewContext(PM_CONTEXT_ARCHIVE, "myarchive");
95 while (pmFetch(npmid, pmidlist, &result) != PM_ERR_EOL) {
96 /*
97 * process real metric values as of result->timestamp
98 */
99 . . .
100 pmFreeResult(result);
101 }
102 Alternatively, to replay interpolated metrics from the archive in re‐
104 verse chronological order, at 10 second intervals (of recorded time),
105 the following code fragment could be used.
106 struct timeval mytime;
108 mytime.tv_sec = PM_MAX_TIME_T; /* or use pmGetArchiveEnd(&mtime) */
110 pmSetMode(PM_MODE_BACK, &mytime, 0);
111 pmFetchArchive(&result);
112 mytime = result->timestamp;
113 pmFreeResult(result);
114 pmSetMode(PM_MODE_INTERP | PM_XTB_SET(PM_TIME_SEC), &mytime, -10);
115 while (pmFetch(numpmid, pmidlist, &result) != PM_ERR_EOL) {
117 /*
118 * process interpolated metric values as of
119 * result->timestamp
120 */
121 . . .
122 pmFreeResult(result);
123 }
124 To perform the same operations, using high resolution time:
126 struct timespec mytime, mydelta = { -10, 0 };
128 mytime.tv_sec = PM_MAX_TIME_T; /* or use pmGetHighResArchiveEnd(&mtime) */
130 pmSetModeHighRes(PM_MODE_BACK, &mytime, NULL);
131 pmFetchHighResArchive(&result);
132 mytime = result->timestamp;
133 pmFreeHighResResult(result);
134 pmSetModeHighRes(PM_MODE_INTERP, &mytime, &mydelta);
135 while (pmFetchHighRes(numpmid, pmidlist, &result) != PM_ERR_EOL) {
137 /*
138 * process interpolated metric values as of
139 * result->timestamp
140 */
141 . . .
142 pmFreeHighResResult(result);
143 }
144
146 The simplest mechanism to set large values for delta is to use the pm‐
147 SetModeHighRes interface. However, the pmSetMode interface supports
148 the XTB (eXtended Time Base) mechanism to allow for values in units
149 other than milliseconds.
150 Because the delta parameter to pmSetMode is an int and treated as mil‐
152 liseconds by default there is a limit on the maximum absolute value of
153 delta that can be specified with this default interpretation, namely
154 about 24 days if a signed int has 31 bits of precision. To accommodate
155 longer values of delta the high-order bits of the mode parameter is
156 also used to optionally set the units of time for the delta parameter.
157 To specify the units of time use the PM_XTB_SET macro with one of the
158 values PM_TIME_NSEC, PM_TIME_MSEC, PM_TIME_SEC, etc. to set the mode
159 as follows:
160 PM_MODE_INTERP | PM_XTB_SET(PM_TIME_XXXX)
162 The following code shows how this could be done if the desired delta is
164 initially encoded in interval (a struct timeval).
165 struct timeval interval;
167 int mode;
168 mode = ...
170 if (abs(interval.tv_sec / (3600*24)) <= 24) {
172 /* default encoding of milliseconds is fine */
173 mode = PM_MODE_INTERP;
174 delta = interval.tv_sec * 1000 + (interval.tv_usec + 500)/ 1000;
175 }
176 else {
177 /* encode delta in units of seconds */
178 mode = PM_MODE_INTERP | PM_XTB_SET(PM_TIME_SEC);
179 delta = interval.tv_sec + (interval.tv_usec + 500000)/ 1000000;
180 }
181 For millisecond encoding of delta, using PM_XTB_SET(PM_TIME_MSEC) is
183 functionally equivalent to not using PM_XTB_SET at all.
184
186 PM_ERR_MODE
187 The mode parameter is invalid
188
190 PMAPI(3), pmFetch(3), pmFetchArchive(3), pmGetInDom(3), pm‐
191 LookupDesc(3), pmLookupInDom(3) and pmNameInDom(3).
192Performance Co-Pilot PCP PMSETMODE(3)