pmdiff(1)

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 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.

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

   -x   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   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 archive set.

   -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).

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