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. 120 121--time:: 122 Analyze samples within given time window. It supports time 123 percent with multiple time ranges. Time string is 'a%/n,b%/m,...' 124 or 'a%-b%,c%-%d,...'. 125 126 For example: 127 128 Select the second 10% time slice to diff: 129 130 perf diff --time 10%/2 131 132 Select from 0% to 10% time slice to diff: 133 134 perf diff --time 0%-10% 135 136 Select the first and the second 10% time slices to diff: 137 138 perf diff --time 10%/1,10%/2 139 140 Select from 0% to 10% and 30% to 40% slices to diff: 141 142 perf diff --time 0%-10%,30%-40% 143 144 It also supports analyzing samples within a given time window 145 <start>,<stop>. Times have the format seconds.microseconds. If 'start' 146 is not given (i.e., time string is ',x.y') then analysis starts at 147 the beginning of the file. If stop time is not given (i.e, time 148 string is 'x.y,') then analysis goes to the end of the file. Time string is 149 'a1.b1,c1.d1:a2.b2,c2.d2'. Use ':' to separate timestamps for different 150 perf.data files. 151 152 For example, we get the timestamp information from 'perf script'. 153 154 perf script -i perf.data.old 155 mgen 13940 [000] 3946.361400: ... 156 157 perf script -i perf.data 158 mgen 13940 [000] 3971.150589 ... 159 160 perf diff --time 3946.361400,:3971.150589, 161 162 It analyzes the perf.data.old from the timestamp 3946.361400 to 163 the end of perf.data.old and analyzes the perf.data from the 164 timestamp 3971.150589 to the end of perf.data. 165 166--cpu:: Only diff samples for the list of CPUs provided. Multiple CPUs can 167 be provided as a comma-separated list with no space: 0,1. Ranges of 168 CPUs are specified with -: 0-2. Default is to report samples on all 169 CPUs. 170 171--pid=:: 172 Only diff samples for given process ID (comma separated list). 173 174--tid=:: 175 Only diff samples for given thread ID (comma separated list). 176 177COMPARISON 178---------- 179The comparison is governed by the baseline file. The baseline perf.data 180file is iterated for samples. All other perf.data files specified on 181the command line are searched for the baseline sample pair. If the pair 182is found, specified computation is made and result is displayed. 183 184All samples from non-baseline perf.data files, that do not match any 185baseline entry, are displayed with empty space within baseline column 186and possible computation results (delta) in their related column. 187 188Example files samples: 189- file A with samples f1, f2, f3, f4, f6 190- file B with samples f2, f4, f5 191- file C with samples f1, f2, f5 192 193Example output: 194 x - computation takes place for pair 195 b - baseline sample percentage 196 197- perf diff A B C 198 199 baseline/A compute/B compute/C samples 200 --------------------------------------- 201 b x f1 202 b x x f2 203 b f3 204 b x f4 205 b f6 206 x x f5 207 208- perf diff B A C 209 210 baseline/B compute/A compute/C samples 211 --------------------------------------- 212 b x x f2 213 b x f4 214 b x f5 215 x x f1 216 x f3 217 x f6 218 219- perf diff C B A 220 221 baseline/C compute/B compute/A samples 222 --------------------------------------- 223 b x f1 224 b x x f2 225 b x f5 226 x f3 227 x x f4 228 x f6 229 230COMPARISON METHODS 231------------------ 232delta 233~~~~~ 234If specified the 'Delta' column is displayed with value 'd' computed as: 235 236 d = A->period_percent - B->period_percent 237 238with: 239 - A/B being matching hist entry from data/baseline file specified 240 (or perf.data/perf.data.old) respectively. 241 242 - period_percent being the % of the hist entry period value within 243 single data file 244 245 - with filtering by -C, -d and/or -S, period_percent might be changed 246 relative to how entries are filtered. Use --percentage=absolute to 247 prevent such fluctuation. 248 249delta-abs 250~~~~~~~~~ 251Same as 'delta` method, but sort the result with the absolute values. 252 253ratio 254~~~~~ 255If specified the 'Ratio' column is displayed with value 'r' computed as: 256 257 r = A->period / B->period 258 259with: 260 - A/B being matching hist entry from data/baseline file specified 261 (or perf.data/perf.data.old) respectively. 262 263 - period being the hist entry period value 264 265wdiff:WEIGHT-B,WEIGHT-A 266~~~~~~~~~~~~~~~~~~~~~~~ 267If specified the 'Weighted diff' column is displayed with value 'd' computed as: 268 269 d = B->period * WEIGHT-A - A->period * WEIGHT-B 270 271 - A/B being matching hist entry from data/baseline file specified 272 (or perf.data/perf.data.old) respectively. 273 274 - period being the hist entry period value 275 276 - WEIGHT-A/WEIGHT-B being user supplied weights in the the '-c' option 277 behind ':' separator like '-c wdiff:1,2'. 278 - WEIGHT-A being the weight of the data file 279 - WEIGHT-B being the weight of the baseline data file 280 281SEE ALSO 282-------- 283linkperf:perf-record[1], linkperf:perf-report[1] 284