PERF-DIFF(1) perf Manual PERF-DIFF(1)NAMEperf-diff - Read perf.data files and display the differential profile
SYNOPSIS
perf diff [baseline file] [data file1] [[data file2] ... ]
DESCRIPTION
This command displays the performance difference amongst two or more
perf.data files captured via perf record.
If no parameters are passed it will assume perf.data.old and perf.data.
The differential profile is displayed only for events matching both
specified perf.data files.
OPTIONS-D, --dump-raw-trace
Dump raw trace in ASCII.
-m, --modules
Load module symbols. WARNING: use only with -k and LIVE kernel
-d, --dsos=
Only consider symbols in these dsos. CSV that understands
file://filename entries.
-C, --comms=
Only consider symbols in these comms. CSV that understands
file://filename entries.
-S, --symbols=
Only consider these symbols. CSV that understands file://filename
entries.
-s, --sort=
Sort by key(s): pid, comm, dso, symbol.
-t, --field-separator=
Use a special separator character and don’t pad with spaces,
replacing all occurrences of this separator in symbol names (and
other output) with a . character, that thus it’s the only non
valid separator.
-v, --verbose
Be verbose, for instance, show the raw counts in addition to the
diff.
-f, --force
Don’t complain, do it.
--symfs=<directory>
Look for files with symbols relative to this directory.
-b, --baseline-only
Show only items with match in baseline.
-c, --compute
Differential computation selection - delta,ratio,wdiff (default is
delta). See COMPARISON METHODS section for more info.
-p, --period
Show period values for both compared hist entries.
-F, --formula
Show formula for given computation.
-o, --order
Specify compute sorting column number.
COMPARISON
The comparison is governed by the baseline file. The baseline perf.data
file is iterated for samples. All other perf.data files specified on
the command line are searched for the baseline sample pair. If the pair
is found, specified computation is made and result is displayed.
All samples from non-baseline perf.data files, that do not match any
baseline entry, are displayed with empty space within baseline column
and possible computation results (delta) in their related column.
Example files samples: - file A with samples f1, f2, f3, f4, f6 - file
B with samples f2, f4, f5 - file C with samples f1, f2, f5
Example output: x - computation takes place for pair b - baseline
sample percentage
· perf diff A B C
baseline/A compute/B compute/C samples
---------------------------------------
b x f1
b x x f2
b f3
b x f4
b f6
x x f5
· perf diff B A C
baseline/B compute/A compute/C samples
---------------------------------------
b x x f2
b x f4
b x f5
x x f1
x f3
x f6
· perf diff C B A
baseline/C compute/B compute/A samples
---------------------------------------
b x f1
b x x f2
b x f5
x f3
x x f4
x f6
COMPARISON METHODS
delta
If specified the Delta column is displayed with value d computed as:
d = A->period_percent - B->period_percent
with: - A/B being matching hist entry from data/baseline file specified
(or perf.data/perf.data.old) respectively.
· period_percent being the % of the hist entry period value within
single data file
ratio
If specified the Ratio column is displayed with value r computed as:
r = A->period / B->period
with: - A/B being matching hist entry from data/baseline file specified
(or perf.data/perf.data.old) respectively.
· period being the hist entry period value
wdiff:WEIGHT-B,WEIGHT-A
If specified the Weighted diff column is displayed with value d
computed as:
d = B->period * WEIGHT-A - A->period * WEIGHT-B
· A/B being matching hist entry from data/baseline file specified (or
perf.data/perf.data.old) respectively.
· period being the hist entry period value
· WEIGHT-A/WEIGHT-B being user suplied weights in the the -c option
behind : separator like -c wdiff:1,2.
· WIEGHT-A being the weight of the data file
· WIEGHT-B being the weight of the baseline data file
SEE ALSOperf-record(1)perf 11/26/2013 PERF-DIFF(1)
