| 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. |
| |
| 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 |
| |
| -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 warnings or messages. (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 |
| ---------- |
| 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 |
| |
| - 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 |
| -------- |
| linkperf:perf-record[1], linkperf:perf-report[1] |
