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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FILES | PCP ENVIRONMENT | SEE ALSO | COLOPHON |
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PMDIFF(1) General Commands Manual PMDIFF(1)
pmdiff - compares archives and report significant differences
pmdiff [-dzV?] [-B starttime] [-E endtime] [-p precision] [-q
thres] [-S starttime] [--skip-excluded] [--skip-missing] [-T
endtime] [-x metric] [-X file] [-Z timezone] archive1 [archive2]
pmdiff compares the average values for every metric in either one
or two sets of archives, in a given time window, for changes that
are likely to be of interest when searching for performance
regressions.
The archive specifiers archive1 and archive2 may be comma-
separated lists of names, each of which may be the base name of
an archive or the name of a directory containing one or more
archives. Each archive in the resulting set of archives must have
been previously created using pmlogger(1). The pmlogsummary(1)
utility is used to obtain the average values used for comparison.
There are two sorts of invocation of the tool: with either one or
two sets of archives.
In the first case, the only sensible command line requires use of
all four time window arguments. These are specified using the
same time window format described in PCPIntro(1), and are
-S/--start and -T/--finish for the start and end times of the
first time window of interest in the archive set, and -B/--before
and -E/--end for the start and end times of the second time
window of interest.
In the second case, with two sets of archives, the -B/--before
and -E/--end options might be unnecessary. This might be the
case, for example, when comparing the same time window of two
consecutive days (usually two separate sets of archives), or a
time window on the same day of different weeks.
In either case, pmdiff produces a sorted summary of those metrics
in the specified window whose values have deviated the most from
a minimal threshold. The level of deviation is calculated by
dividing the average value of each metric in both logs, and then
calculating whether the ratio falls outside of a range considered
normal. This ratio can be adjusted using the -q/--threshold
option, and by default it is 2 (i.e. report all metrics with
average values that have more than doubled in the two time
windows or more than halved in the two time windows).
If the baseline value is zero and the comparison value is non-
zero, the ratio is reported as ``|+|'' (infinitely large). If
the comparison value is zero and the baseline value is non-zero,
the ratio is reported as ``|-|'' (infinitely small).
Reported metrics are sorted in ascending ratio order.
Should any metrics be present in one window but missing from the
other, a diagnostic will be displayed listing each missing metric
and the archive set from which it was missing.
Metrics with counter semantics are converted to rates before
being evaluated.
The available command line options are:
-d, --keep
Debug mode, keep intermediate files.
-B time, --begin=time
Start time for the second time window.
-E time, --end=time
End time for the second time window.
-p precision, --precision=precision
Print all floating point numbers with precision digits after
the decimal place.
-q threshold, --threshold=threshold
Change the threshold for interesting metrics, see above for
more details.
-S time, --start=time
Start time of the first time window.
-T time, --finish=time
End time of the first time window.
-V, --version
Display version number and exit.
-x metric
Compare each metric in each archive set in the time windows
specified to a given egrep(1) pattern, excluding those that
match from the report output.
-X file
Allows a file to be specified which containing egrep(1)
patterns which are applied to the metric names to optionally
exclude some from the report.
-z, --hostzone
Use the local timezone from the given archive set.
-Z timezone, --timezone=timezone
Changes the timezone in the archive labels to timezone in
the format of the environment variable TZ as described in
environ(7).
-?, --help
Display usage message and exit.
--skip-excluded
Cull the list of names of metrics being excluded from the
output.
--skip-missing
By default, pmdiff will report the names of any metrics that
are in one archive set but not the other. This option
suppresses that reporting.
$PCP_LOG_DIR/pmlogger/<hostname>
Default directory for PCP archives containing performance
metric values collected from the host hostname.
Environment variables with the prefix PCP_ are used to
parameterize the file and directory names used by PCP. On each
installation, the file /etc/pcp.conf contains the local values
for these variables. The $PCP_CONF variable may be used to
specify an alternative configuration file, as described in
pcp.conf(5).
PCPIntro(1), pmlogger(1), pmlogsummary(1), egrep(1), pcp.conf(5)
and pcp.env(5).
This page is part of the PCP (Performance Co-Pilot) project.
Information about the project can be found at
⟨http://www.pcp.io/⟩. If you have a bug report for this manual
page, send it to [email protected]. 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
[email protected]
Performance Co-Pilot PCP PMDIFF(1)
Pages that refer to this page: pmrep(1)
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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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