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, cycles, 94 delta-abs (default is delta-abs). Default can be changed using 95 diff.compute config option. See COMPARISON METHODS section for 96 more info. 97 98--cycles-hist:: 99 Report a histogram and the standard deviation for cycles data. 100 It can help us to judge if the reported cycles data is noisy or 101 not. This option should be used with '-c cycles'. 102 103-p:: 104--period:: 105 Show period values for both compared hist entries. 106 107-F:: 108--formula:: 109 Show formula for given computation. 110 111-o:: 112--order:: 113 Specify compute sorting column number. 0 means sorting by baseline 114 overhead and 1 (default) means sorting by computed value of column 1 115 (data from the first file other base baseline). Values more than 1 116 can be used only if enough data files are provided. 117 The default value can be set using the diff.order config option. 118 119--percentage:: 120 Determine how to display the overhead percentage of filtered entries. 121 Filters can be applied by --comms, --dsos and/or --symbols options. 122 123 "relative" means it's relative to filtered entries only so that the 124 sum of shown entries will be always 100%. "absolute" means it retains 125 the original value before and after the filter is applied. 126 127--time:: 128 Analyze samples within given time window. It supports time 129 percent with multiple time ranges. Time string is 'a%/n,b%/m,...' 130 or 'a%-b%,c%-%d,...'. 131 132 For example: 133 134 Select the second 10% time slice to diff: 135 136 perf diff --time 10%/2 137 138 Select from 0% to 10% time slice to diff: 139 140 perf diff --time 0%-10% 141 142 Select the first and the second 10% time slices to diff: 143 144 perf diff --time 10%/1,10%/2 145 146 Select from 0% to 10% and 30% to 40% slices to diff: 147 148 perf diff --time 0%-10%,30%-40% 149 150 It also supports analyzing samples within a given time window 151 <start>,<stop>. Times have the format seconds.nanoseconds. If 'start' 152 is not given (i.e. time string is ',x.y') then analysis starts at 153 the beginning of the file. If stop time is not given (i.e. time 154 string is 'x.y,') then analysis goes to the end of the file. 155 Multiple ranges can be separated by spaces, which requires the argument 156 to be quoted e.g. --time "1234.567,1234.789 1235," 157 Time string is'a1.b1,c1.d1:a2.b2,c2.d2'. Use ':' to separate timestamps 158 for different perf.data files. 159 160 For example, we get the timestamp information from 'perf script'. 161 162 perf script -i perf.data.old 163 mgen 13940 [000] 3946.361400: ... 164 165 perf script -i perf.data 166 mgen 13940 [000] 3971.150589 ... 167 168 perf diff --time 3946.361400,:3971.150589, 169 170 It analyzes the perf.data.old from the timestamp 3946.361400 to 171 the end of perf.data.old and analyzes the perf.data from the 172 timestamp 3971.150589 to the end of perf.data. 173 174--cpu:: Only diff samples for the list of CPUs provided. Multiple CPUs can 175 be provided as a comma-separated list with no space: 0,1. Ranges of 176 CPUs are specified with -: 0-2. Default is to report samples on all 177 CPUs. 178 179--pid=:: 180 Only diff samples for given process ID (comma separated list). 181 182--tid=:: 183 Only diff samples for given thread ID (comma separated list). 184 185--stream:: 186 Enable hot streams comparison. Stream can be a callchain which is 187 aggregated by the branch records from samples. 188 189COMPARISON 190---------- 191The comparison is governed by the baseline file. The baseline perf.data 192file is iterated for samples. All other perf.data files specified on 193the command line are searched for the baseline sample pair. If the pair 194is found, specified computation is made and result is displayed. 195 196All samples from non-baseline perf.data files, that do not match any 197baseline entry, are displayed with empty space within baseline column 198and possible computation results (delta) in their related column. 199 200Example files samples: 201- file A with samples f1, f2, f3, f4, f6 202- file B with samples f2, f4, f5 203- file C with samples f1, f2, f5 204 205Example output: 206 x - computation takes place for pair 207 b - baseline sample percentage 208 209- perf diff A B C 210 211 baseline/A compute/B compute/C samples 212 --------------------------------------- 213 b x f1 214 b x x f2 215 b f3 216 b x f4 217 b f6 218 x x f5 219 220- perf diff B A C 221 222 baseline/B compute/A compute/C samples 223 --------------------------------------- 224 b x x f2 225 b x f4 226 b x f5 227 x x f1 228 x f3 229 x f6 230 231- perf diff C B A 232 233 baseline/C compute/B compute/A samples 234 --------------------------------------- 235 b x f1 236 b x x f2 237 b x f5 238 x f3 239 x x f4 240 x f6 241 242COMPARISON METHODS 243------------------ 244delta 245~~~~~ 246If specified the 'Delta' column is displayed with value 'd' computed as: 247 248 d = A->period_percent - B->period_percent 249 250with: 251 - A/B being matching hist entry from data/baseline file specified 252 (or perf.data/perf.data.old) respectively. 253 254 - period_percent being the % of the hist entry period value within 255 single data file 256 257 - with filtering by -C, -d and/or -S, period_percent might be changed 258 relative to how entries are filtered. Use --percentage=absolute to 259 prevent such fluctuation. 260 261delta-abs 262~~~~~~~~~ 263Same as 'delta` method, but sort the result with the absolute values. 264 265ratio 266~~~~~ 267If specified the 'Ratio' column is displayed with value 'r' computed as: 268 269 r = A->period / B->period 270 271with: 272 - A/B being matching hist entry from data/baseline file specified 273 (or perf.data/perf.data.old) respectively. 274 275 - period being the hist entry period value 276 277wdiff:WEIGHT-B,WEIGHT-A 278~~~~~~~~~~~~~~~~~~~~~~~ 279If specified the 'Weighted diff' column is displayed with value 'd' computed as: 280 281 d = B->period * WEIGHT-A - A->period * WEIGHT-B 282 283 - A/B being matching hist entry from data/baseline file specified 284 (or perf.data/perf.data.old) respectively. 285 286 - period being the hist entry period value 287 288 - WEIGHT-A/WEIGHT-B being user supplied weights in the the '-c' option 289 behind ':' separator like '-c wdiff:1,2'. 290 - WEIGHT-A being the weight of the data file 291 - WEIGHT-B being the weight of the baseline data file 292 293cycles 294~~~~~~ 295If specified the '[Program Block Range] Cycles Diff' column is displayed. 296It displays the cycles difference of same program basic block amongst 297two perf.data. The program basic block is the code between two branches. 298 299'[Program Block Range]' indicates the range of a program basic block. 300Source line is reported if it can be found otherwise uses symbol+offset 301instead. 302 303SEE ALSO 304-------- 305linkperf:perf-record[1], linkperf:perf-report[1] 306