| 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 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, delta-abs | |
| (default is delta-abs). Default can be changed using diff.compute | |
| config option. 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. 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.microseconds. 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. 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). | |
| 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 | |
| SEE ALSO | |
| -------- | |
| linkperf:perf-record[1], linkperf:perf-report[1] |