pmlogreduce(1) — Linux manual page


PMLOGREDUCE(1)           General Commands Manual          PMLOGREDUCE(1)

NAME         top

       pmlogreduce - temporal reduction of Performance Co-Pilot archives

SYNOPSIS         top

       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

       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

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

       -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 records have been written to the output

              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

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

DATA REDUCTION         top

       The statistical and temporal reduction follows the following

       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

       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

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 used.

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

            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.


       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

SEE ALSO         top

       PCPIntro(1), pmlc(1), pmlogdump(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 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

Performance Co-Pilot               PCP                    PMLOGREDUCE(1)

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