1perf-diff(1) 2============ 3 4NAME 5---- 6perf-diff - Read perf.data files and display the differential profile 7 8SYNOPSIS 9-------- 10[verse] 11'perf diff' [baseline file] [data file1] [[data file2] ... ] 12 13DESCRIPTION 14----------- 15This command displays the performance difference amongst two or more perf.data 16files captured via perf record. 17 18If no parameters are passed it will assume perf.data.old and perf.data. 19 20The differential profile is displayed only for events matching both 21specified perf.data files. 22 23If no parameters are passed the samples will be sorted by dso and symbol. 24As the perf.data files could come from different binaries, the symbols addresses 25could vary. So perf diff is based on the comparison of the files and 26symbols name. 27 28OPTIONS 29------- 30-D:: 31--dump-raw-trace:: 32 Dump raw trace in ASCII. 33 34--kallsyms=<file>:: 35 kallsyms pathname 36 37-m:: 38--modules:: 39 Load module symbols. WARNING: use only with -k and LIVE kernel 40 41-d:: 42--dsos=:: 43 Only consider symbols in these dsos. CSV that understands 44 file://filename entries. This option will affect the percentage 45 of the Baseline/Delta column. See --percentage for more info. 46 47-C:: 48--comms=:: 49 Only consider symbols in these comms. CSV that understands 50 file://filename entries. This option will affect the percentage 51 of the Baseline/Delta column. See --percentage for more info. 52 53-S:: 54--symbols=:: 55 Only consider these symbols. CSV that understands 56 file://filename entries. This option will affect the percentage 57 of the Baseline/Delta column. See --percentage for more info. 58 59-s:: 60--sort=:: 61 Sort by key(s): pid, comm, dso, symbol, cpu, parent, srcline. 62 Please see description of --sort in the perf-report man page. 63 64-t:: 65--field-separator=:: 66 67 Use a special separator character and don't pad with spaces, replacing 68 all occurrences of this separator in symbol names (and other output) 69 with a '.' character, that thus it's the only non valid separator. 70 71-v:: 72--verbose:: 73 Be verbose, for instance, show the raw counts in addition to the 74 diff. 75 76-q:: 77--quiet:: 78 Do not show any message. (Suppress -v) 79 80-f:: 81--force:: 82 Don't do ownership validation. 83 84--symfs=<directory>:: 85 Look for files with symbols relative to this directory. 86 87-b:: 88--baseline-only:: 89 Show only items with match in baseline. 90 91-c:: 92--compute:: 93 Differential computation selection - delta, ratio, wdiff, delta-abs 94 (default is delta-abs). Default can be changed using diff.compute 95 config option. See COMPARISON METHODS section for more info. 96 97-p:: 98--period:: 99 Show period values for both compared hist entries. 100 101-F:: 102--formula:: 103 Show formula for given computation. 104 105-o:: 106--order:: 107 Specify compute sorting column number. 0 means sorting by baseline 108 overhead and 1 (default) means sorting by computed value of column 1 109 (data from the first file other base baseline). Values more than 1 110 can be used only if enough data files are provided. 111 The default value can be set using the diff.order config option. 112 113--percentage:: 114 Determine how to display the overhead percentage of filtered entries. 115 Filters can be applied by --comms, --dsos and/or --symbols options. 116 117 "relative" means it's relative to filtered entries only so that the 118 sum of shown entries will be always 100%. "absolute" means it retains 119 the original value before and after the filter is applied. 120 121COMPARISON 122---------- 123The comparison is governed by the baseline file. The baseline perf.data 124file is iterated for samples. All other perf.data files specified on 125the command line are searched for the baseline sample pair. If the pair 126is found, specified computation is made and result is displayed. 127 128All samples from non-baseline perf.data files, that do not match any 129baseline entry, are displayed with empty space within baseline column 130and possible computation results (delta) in their related column. 131 132Example files samples: 133- file A with samples f1, f2, f3, f4, f6 134- file B with samples f2, f4, f5 135- file C with samples f1, f2, f5 136 137Example output: 138 x - computation takes place for pair 139 b - baseline sample percentage 140 141- perf diff A B C 142 143 baseline/A compute/B compute/C samples 144 --------------------------------------- 145 b x f1 146 b x x f2 147 b f3 148 b x f4 149 b f6 150 x x f5 151 152- perf diff B A C 153 154 baseline/B compute/A compute/C samples 155 --------------------------------------- 156 b x x f2 157 b x f4 158 b x f5 159 x x f1 160 x f3 161 x f6 162 163- perf diff C B A 164 165 baseline/C compute/B compute/A samples 166 --------------------------------------- 167 b x f1 168 b x x f2 169 b x f5 170 x f3 171 x x f4 172 x f6 173 174COMPARISON METHODS 175------------------ 176delta 177~~~~~ 178If specified the 'Delta' column is displayed with value 'd' computed as: 179 180 d = A->period_percent - B->period_percent 181 182with: 183 - A/B being matching hist entry from data/baseline file specified 184 (or perf.data/perf.data.old) respectively. 185 186 - period_percent being the % of the hist entry period value within 187 single data file 188 189 - with filtering by -C, -d and/or -S, period_percent might be changed 190 relative to how entries are filtered. Use --percentage=absolute to 191 prevent such fluctuation. 192 193delta-abs 194~~~~~~~~~ 195Same as 'delta` method, but sort the result with the absolute values. 196 197ratio 198~~~~~ 199If specified the 'Ratio' column is displayed with value 'r' computed as: 200 201 r = A->period / B->period 202 203with: 204 - A/B being matching hist entry from data/baseline file specified 205 (or perf.data/perf.data.old) respectively. 206 207 - period being the hist entry period value 208 209wdiff:WEIGHT-B,WEIGHT-A 210~~~~~~~~~~~~~~~~~~~~~~~ 211If specified the 'Weighted diff' column is displayed with value 'd' computed as: 212 213 d = B->period * WEIGHT-A - A->period * WEIGHT-B 214 215 - A/B being matching hist entry from data/baseline file specified 216 (or perf.data/perf.data.old) respectively. 217 218 - period being the hist entry period value 219 220 - WEIGHT-A/WEIGHT-B being user supplied weights in the the '-c' option 221 behind ':' separator like '-c wdiff:1,2'. 222 - WEIGHT-A being the weight of the data file 223 - WEIGHT-B being the weight of the baseline data file 224 225SEE ALSO 226-------- 227linkperf:perf-record[1], linkperf:perf-report[1] 228