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NAME

       perf-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 ALSO

       perf-record(1)