pmlogreduce(1) — Linux manual page


PMLOGREDUCE(1)             General Commands Manual            PMLOGREDUCE(1)

NAME         top

       pmlogreduce - temporal reduction of Performance Co-Pilot archives

SYNOPSIS         top

       $PCP_BINADM_DIR/pmlogreduce [-z?]  [-A align] [-s samples] [-S
       starttime] [-t interval] [-T endtime] [-v volsamples] [-Z timezone]
       input output

DESCRIPTION         top

       pmlogreduce reads one set of Performance Co-Pilot (PCP) archives
       identified by input and creates a temporally reduced PCP archive in
       output.  input is a comma-separated list of names, each of which may
       be the base name of an archive or the name of a directory containing
       one or more archives.  The data reduction involves statistical and
       temporal reduction of samples with an output sampling interval
       defined by the -t option in the output archive (independent of the
       sampling intervals in the input archives), and is further controlled
       by other command line arguments.

       For some metrics, temporal data reduction is not going to be helpful,
       so for metrics with types PM_TYPE_AGGREGATE or PM_TYPE_EVENT, a
       warning is issued if these metrics are found in input and they will
       be skipped and not appear in the output archive.

OPTIONS         top

       The available command line options are:

       -A align, --align=align
            Specify a ``natural'' alignment of the output sample times;
            refer to PCPIntro(1).

       -s samples, --samples=samples
            The argument samples defines the number of samples to be written
            to output.  If samples is 0 or -s is not specified, pmlogreduce
            will sample until the end of the set of PCP archives, or the end
            of the time window as specified by -T, whichever comes first.
            The -s option will override the -T option if it occurs sooner.

       -S starttime, --start=starttime
            Define the start of a time window to restrict the samples
            retrieved from the input archives; refer to PCPIntro(1).

       -t interval, --interval=interval
            Consecutive samples in the output archive will appear with a
            time delta defined by interval; refer to PCPIntro(1).  Note the
            default value is 600 (seconds, i.e. 10 minutes).

       -T endtime, --finish=endtime
            Define the termination of a time window to restrict the samples
            retrieved from the input archives; refer to PCPIntro(1).

       -v volsamples
            The output archive is potentially a multi-volume data set, and
            the -v option causes pmlogreduce to start a new volume after
            volsamples log records have been written to the output archive.

              Independent of any -v option, each volume of an archive is
              limited to no more than 2^31 bytes, so pmlogreduce will
              automatically create a new volume for the archive before this
              limit is reached.

       -z, --hostzone
            Use the local timezone of the host from the input archives when
            displaying the date and time, or interpreting the -S and -T
            options.  The default is to initially use the timezone of the
            local host.

       -Z timezone, --timezone=timezone
            Use timezone when displaying the date and time, or interpreting
            the -S and -T options.  Timezone is in the format of the
            environment variable TZ as described in environ(7).

       -?, --help
            Display usage message and exit.

DATA REDUCTION         top

       The statistical and temporal reduction follows the following rules:

       1.  Consecutive records from input are read without interpolation,
           and at most one output record is written for each interval,
           summarizing the performance data over that period.

       2.  If the semantics of a metric indicates it is instantaneous or
           discrete then output value is computed as the arithmetic mean of
           the observations (if any) over each interval.

       3.  If the semantics of a metric indicates it is a counter then the
           following transformations are applied:
           a)  Metrics with 32-bit precision are promoted to 64-bit
           b)  Any counter wrap (overflow) is noted, and appropriate
               adjustment made in the value of the metric over each
               interval.  This will be correct in the case of a single
               counter wrap, but will silently underestimate in the case
               where more than one counter wrap occurs between consecutive
               observations in the input archives, and silently overestimate
               in the case where a counter reset occurs between consecutive
               observations in the input archives; unfortunately these
               situations cannot be detected, but are believed to be rare
               events for the sort of production monitoring environments
               where pmlogreduce is most likely to be deployed.

       4.  Any changes in instance domains, and indeed all metadata, is

       5.  Any ``mark'' records in the input archives (as created by
           pmlogextract(1)) will be preserved in the output archive, so
           periods where no data is available are maintained, and data
           interpolation will not occur across these periods when the output
           archive is subsequently processed with PCP applications.

CAVEATS         top

       The preamble metrics (pmcd.pmlogger.archive,, and
       pmcd.pmlogger.port), which are automatically recorded by pmlogger at
       the start of the archive, may not be present in the archive output by
       pmlogreduce.  These metrics are only relevant while the archive is
       being created, and have no significance once recording has finished.

DIAGNOSTICS         top

       All error conditions detected by pmlogreduce are reported on stderr
       with textual (if sometimes terse) explanation.

       Should the input archives be corrupted (this can happen if the
       pmlogger instance writing the archive suddenly dies), then
       pmlogreduce will detect and report the position of the corruption in
       the file, and any subsequent information from the input archives will
       not be processed.

       If any error is detected, pmlogreduce will exit with a non-zero

FILES         top

       For each of the input and output archives, several physical files are

            metadata (metric descriptions, instance domains, etc.) for the
            archive log

            initial volume of metrics values (subsequent volumes have
            suffixes 1, 2, ...) - for input these files may have been
            previously compressed with bzip2(1) or gzip(1) and thus may have
            an additional .bz2 or .gz suffix.

            temporal index to support rapid random access to the other files
            in the archive log.


       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).

SEE ALSO         top

       PCPIntro(1), pmdumplog(1), pmlc(1), pmlogextract(1), pmlogger(1),
       pcp.conf(5) and pcp.env(5).

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
       Information about the project can be found at ⟨⟩.
       If you have a bug report for this manual page, send it to  This page was obtained from the project's upstream
       Git repository ⟨⟩ on
       2020-08-13.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-08-11.)  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

Performance Co-Pilot                 PCP                      PMLOGREDUCE(1)

Pages that refer to this page: pmlogextract(1)pmlogrewrite(1)logarchive(5)LOGARCHIVE(5)