bionic (1) pmdiff.1.gz

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).