NAME

       pmdiff - compares archives and report significant differences

SYNOPSIS

       pmdiff   [-d/--keep]   [-z/--hostzone]  [-p/--precision  precision]  [-q/--threshold  thres]  [-S/--start
       starttime] [-T/--finish endtime] [-B/--begin starttime] [-E/--end endtime] [-x metric] [-X file] [--skip-
       excluded] [--skip-missing] [-Z/--timezone timezone] archive1 [archive2]

DESCRIPTION

       pmdiff compares the average values for every metric in either one  or  two  archives,  in  a  given  time
       window, for changes that are likely to be of interest when searching for performance regressions.

       The  archive  log has the base name archive and 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 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,  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 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 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 from which it was missing.

       The  remaining  options  control the specific information to be reported.  Metrics with counter semantics
       are converted to rates before being evaluated.

       -p/--precision
            Print all floating point numbers with precision digits after the decimal place.

       --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 but not  the  other.
            This option suppresses that reporting.

       -x   Compare  each  metric  in  each  archive  in the time windows specified to a given egrep(1) pattern,
            excluding those that match from the report output.

       -X   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   Use the local timezone from the given archives.

       -Z/--timezone
            Changes  the timezone in the archive labels to timezone in the format of the environment variable TZ
            as described in environ(7).

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).

Performance Co-Pilot                                   PCP                                             PMDIFF(1)