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Diffstat (limited to 'tools/perf/Documentation/perf-diff.txt')
| -rw-r--r-- | tools/perf/Documentation/perf-diff.txt | 212 |
1 files changed, 192 insertions, 20 deletions
diff --git a/tools/perf/Documentation/perf-diff.txt b/tools/perf/Documentation/perf-diff.txt index 5b3123d5721f..58efab72d2e5 100644 --- a/tools/perf/Documentation/perf-diff.txt +++ b/tools/perf/Documentation/perf-diff.txt @@ -3,29 +3,37 @@ perf-diff(1) NAME ---- -perf-diff - Read two perf.data files and display the differential profile +perf-diff - Read perf.data files and display the differential profile SYNOPSIS -------- [verse] -'perf diff' [oldfile] [newfile] +'perf diff' [baseline file] [data file1] [[data file2] ... ] DESCRIPTION ----------- -This command displays the performance difference amongst two perf.data files -captured via perf record. +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 ------- -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 @@ -33,21 +41,25 @@ OPTIONS -d:: --dsos=:: Only consider symbols in these dsos. CSV that understands - file://filename entries. + 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. + 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. + 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. + 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=:: @@ -61,9 +73,13 @@ OPTIONS Be verbose, for instance, show the raw counts in addition to the diff. +-q:: +--quiet:: + Do not show any warnings or messages. (Suppress -v) + -f:: --force:: - Don't complain, do it. + Don't do ownership validation. --symfs=<directory>:: Look for files with symbols relative to this directory. @@ -74,10 +90,15 @@ OPTIONS -c:: --compute:: - Differential computation selection - delta,ratio,wdiff (default is delta). - If '+' is specified as a first character, the output is sorted based - on the computation results. - See COMPARISON METHODS section for more info. + 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:: @@ -87,6 +108,137 @@ OPTIONS --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 +---------- +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 @@ -96,12 +248,20 @@ 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 first/second file specified + - 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: @@ -109,25 +269,37 @@ 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 first/second file specified + - 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 -~~~~~ +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 first/second file specified + - 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 + - WEIGHT-A/WEIGHT-B being user supplied weights in 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 -------- -linkperf:perf-record[1] +linkperf:perf-record[1], linkperf:perf-report[1] |