PERF-DIFF(1)							    perf Manual 						      PERF-DIFF(1)

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

       o   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

       o   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

       o   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.

       o   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.

       o   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

       o   A/B being matching hist entry from data/baseline file specified (or perf.data/perf.data.old) respectively.

       o   period being the hist entry period value

       o   WEIGHT-A/WEIGHT-B being user suplied weights in the the -c option behind : separator like -c wdiff:1,2.

       o   WIEGHT-A being the weight of the data file

       o   WIEGHT-B being the weight of the baseline data file

SEE ALSO

       perf-record(1)

perf								    06/30/2014							      PERF-DIFF(1)