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).
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(5).
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).