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  perf-diff(1)
  ============
  
  NAME
  ----
  perf-diff - Read perf.data files and display the differential profile
  
  SYNOPSIS
  --------
  [verse]
  '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
  --------
  linkperf:perf-record[1]