perf-diff(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | COMPARISON | COMPARISON METHODS | SEE ALSO | COLOPHON

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

NAME         top

       perf-diff - Read perf.data files and display the differential
       profile

SYNOPSIS         top

       perf diff [baseline file] [data file1] [[data file2] ... ]

DESCRIPTION         top

       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.

       If no parameters are passed the samples will be sorted by dso and
       symbol. As the perf.data files could come from different
       binaries, the symbols addresses could vary. So perf diff is based
       on the comparison of the files and symbols name.

OPTIONS         top

       -D, --dump-raw-trace
           Dump raw trace in ASCII.

       --kallsyms=<file>
           kallsyms pathname

       -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. This option will affect the
           percentage of the Baseline/Delta column. See --percentage for
           more info.

       -C, --comms=
           Only consider symbols in these comms. CSV that understands
           file://filename entries. This option will affect the
           percentage of the Baseline/Delta column. See --percentage for
           more info.

       -S, --symbols=
           Only consider these symbols. CSV that understands
           file://filename entries. This option will affect the
           percentage of the Baseline/Delta column. See --percentage for
           more info.

       -s, --sort=
           Sort by key(s): pid, comm, dso, symbol, cpu, parent, srcline.
           Please see description of --sort in the perf-report man page.

       -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.

       -q, --quiet
           Do not show any message. (Suppress -v)

       -f, --force
           Don’t do ownership validation.

       --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,
           cycles, delta-abs (default is delta-abs). Default can be
           changed using diff.compute config option. See COMPARISON
           METHODS section for more info.

       --cycles-hist
           Report a histogram and the standard deviation for cycles
           data. It can help us to judge if the reported cycles data is
           noisy or not. This option should be used with -c cycles.

       -p, --period
           Show period values for both compared hist entries.

       -F, --formula
           Show formula for given computation.

       -o, --order
           Specify compute sorting column number. 0 means sorting by
           baseline overhead and 1 (default) means sorting by computed
           value of column 1 (data from the first file other base
           baseline). Values more than 1 can be used only if enough data
           files are provided. The default value can be set using the
           diff.order config option.

       --percentage
           Determine how to display the overhead percentage of filtered
           entries. Filters can be applied by --comms, --dsos and/or
           --symbols options.

               "relative" means it's relative to filtered entries only so that the
               sum of shown entries will be always 100%.  "absolute" means it retains
               the original value before and after the filter is applied.

       --time
           Analyze samples within given time window. It supports time
           percent with multiple time ranges. Time string is
           a%/n,b%/m,...  or a%-b%,c%-%d,....

               For example:

               Select the second 10% time slice to diff:

               perf diff --time 10%/2

               Select from 0% to 10% time slice to diff:

               perf diff --time 0%-10%

               Select the first and the second 10% time slices to diff:

               perf diff --time 10%/1,10%/2

               Select from 0% to 10% and 30% to 40% slices to diff:

               perf diff --time 0%-10%,30%-40%

               It also supports analyzing samples within a given time window
               <start>,<stop>. Times have the format seconds.nanoseconds. If 'start'
               is not given (i.e. time string is ',x.y') then analysis starts at
               the beginning of the file. If stop time is not given (i.e. time
               string is 'x.y,') then analysis goes to the end of the file.
               Multiple ranges can be separated by spaces, which requires the argument
               to be quoted e.g. --time "1234.567,1234.789 1235,"
               Time string is'a1.b1,c1.d1:a2.b2,c2.d2'. Use ':' to separate timestamps
               for different perf.data files.

               For example, we get the timestamp information from 'perf script'.

               perf script -i perf.data.old
                 mgen 13940 [000]  3946.361400: ...

               perf script -i perf.data
                 mgen 13940 [000]  3971.150589 ...

               perf diff --time 3946.361400,:3971.150589,

               It analyzes the perf.data.old from the timestamp 3946.361400 to
               the end of perf.data.old and analyzes the perf.data from the
               timestamp 3971.150589 to the end of perf.data.

       --cpu
           Only diff samples for the list of CPUs provided. Multiple
           CPUs can be provided as a comma-separated list with no space:
           0,1. Ranges of CPUs are specified with -: 0-2. Default is to
           report samples on all CPUs.

       --pid=
           Only diff samples for given process ID (comma separated
           list).

       --tid=
           Only diff samples for given thread ID (comma separated list).

       --stream
           Enable hot streams comparison. Stream can be a callchain
           which is aggregated by the branch records from samples.

COMPARISON         top

       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         top

   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

       •   with filtering by -C, -d and/or -S, period_percent might be
           changed relative to how entries are filtered. Use
           --percentage=absolute to prevent such fluctuation.

   delta-abs
       Same as 'delta` method, but sort the result with the absolute
       values.

   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 supplied weights in the the -c
           option behind : separator like -c wdiff:1,2.

       •   WEIGHT-A being the weight of the data file

       •   WEIGHT-B being the weight of the baseline data file

   cycles
       If specified the [Program Block Range] Cycles Diff column is
       displayed. It displays the cycles difference of same program
       basic block amongst two perf.data. The program basic block is the
       code between two branches.

       [Program Block Range] indicates the range of a program basic
       block. Source line is reported if it can be found otherwise uses
       symbol+offset instead.

SEE ALSO         top

       perf-record(1), perf-report(1)

COLOPHON         top

       This page is part of the perf (Performance analysis tools for
       Linux (in Linux source tree)) project.  Information about the
       project can be found at 
       ⟨https://perf.wiki.kernel.org/index.php/Main_Page⟩.  If you have a
       bug report for this manual page, send it to
       linux-kernel@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git⟩
       on 2021-08-27.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-26.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

perf                           2020-10-14                   PERF-DIFF(1)

Pages that refer to this page: perf(1)perf-kvm(1)