1PMDIFF(1) General Commands Manual PMDIFF(1)
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6 pmdiff - compares archives and report significant differences
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9 pmdiff [-d/--keep] [-z/--hostzone] [-p/--precision precision]
10 [-q/--threshold thres] [-S/--start starttime] [-T/--finish endtime]
11 [-B/--begin starttime] [-E/--end endtime] [-x metric] [-X file]
12 [--skip-excluded] [--skip-missing] [-Z/--timezone timezone] archive1
13 [archive2]
14
16 pmdiff compares the average values for every metric in either one or
17 two sets of archives, in a given time window, for changes that are
18 likely to be of interest when searching for performance regressions.
19 The archive specifiers archive1 and archive2 may be comma-separated
21 lists of names, each of which may be the base name of an archive or the
22 name of a directory containing one or more archives. Each archive in
23 the resulting set of archives must have been previously created using
24 pmlogger(1). The pmlogsummary(1) utility is used to obtain the average
25 values used for comparison.
26 There are two sorts of invocation of the tool: with either one or two
28 sets of archives.
29 In the first case, the only sensible command line requires use of all
31 four time window arguments. These are specified using the same time
32 window format described in PCPIntro(1), and are -S/--start and
33 -T/--finish for the start and end times of the first time window of
34 interest in the archive set, and -B/--before and -E/--end for the start
35 and end times of the second time window of interest.
36 In the second case, with two sets of archives, the -B/--before and
38 -E/--end options might be unnecessary. This might be the case, for
39 example, when comparing the same time window of two consecutive days
40 (usually two separate sets of archives), or a time window on the same
41 day of different weeks.
42 In either case, pmdiff produces a sorted summary of those metrics in
44 the specified window whose values have deviated the most from a minimal
45 threshold. The level of deviation is calculated by dividing the aver‐
46 age value of each metric in both logs, and then calculating whether the
47 ratio falls outside of a range considered normal. This ratio can be
48 adjusted using the -q/--threshold option, and by default it is 2 (i.e.
49 report all metrics with average values that have more than doubled in
50 the two time windows or more than halved in the two time windows).
51 If the baseline value is zero and the comparison value is non-zero, the
53 ratio is reported as ``|+|'' (infinitely large). If the comparison
54 value is zero and the baseline value is non-zero, the ratio is reported
55 as ``|-|'' (infinitely small).
56 Reported metrics are sorted in ascending ratio order.
58 Should any metrics be present in one window but missing from the other,
60 a diagnostic will be displayed listing each missing metric and the ar‐
61 chive set from which it was missing.
62 The remaining options control the specific information to be reported.
64 Metrics with counter semantics are converted to rates before being
65 evaluated.
66 -p/--precision
68 Print all floating point numbers with precision digits after the
69 decimal place.
70 --skip-excluded
72 Cull the list of names of metrics being excluded from the output.
73 --skip-missing
75 By default, pmdiff will report the names of any metrics that are
76 in one archive set but not the other. This option suppresses that
77 reporting.
78 -x Compare each metric in each archive set in the time windows speci‐
80 fied to a given egrep(1) pattern, excluding those that match from
81 the report output.
82 -X Allows a file to be specified which containing egrep(1) patterns
84 which are applied to the metric names to optionally exclude some
85 from the report.
86 -z Use the local timezone from the given archive set.
88 -Z/--timezone
90 Changes the timezone in the archive labels to timezone in the for‐
91 mat of the environment variable TZ as described in environ(7).
92
94 $PCP_LOG_DIR/pmlogger/hostname
95 Default directory for PCP archives containing performance
96 metric values collected from the host hostname.
97
99 Environment variables with the prefix PCP_ are used to parameterize the
100 file and directory names used by PCP. On each installation, the file
101 /etc/pcp.conf contains the local values for these variables. The
102 $PCP_CONF variable may be used to specify an alternative configuration
103 file, as described in pcp.conf(5).
104
106 PCPIntro(1), pmlogger(1), pmlogsummary(1), egrep(1), pcp.conf(5) and
107 pcp.env(5).
108Performance Co-Pilot PCP PMDIFF(1)