NAME

       pmdiff - compares archives and report significant differences

SYNOPSIS

       pmdiff  [-dzV?]   [-B starttime] [-E endtime] [-p precision] [-q thres] [-S starttime] [-T
       endtime] [-x metric] [-X file] [-Z timezone] [--skip-excluded]  [--skip-missing]  archive1
       [archive2]

DESCRIPTION

       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.

OPTIONS

       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.

FILES

       $PCP_LOG_DIR/pmlogger/<hostname>
            Default  directory  for  PCP  archives containing performance metric values collected
            from the host hostname.

PCP ENVIRONMENT

       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

       PCPIntro(1), pmlogger(1), pmlogsummary(1), egrep(1), pcp.conf(5) and pcp.env(5).