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.nanoseconds. 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. 149 Multiple ranges can be separated by spaces, which requires the argument 150 to be quoted e.g. --time "1234.567,1234.789 1235," 151 Time string is'a1.b1,c1.d1:a2.b2,c2.d2'. Use ':' to separate timestamps 152 for different perf.data files. 153 154 For example, we get the timestamp information from 'perf script'. 155 156 perf script -i perf.data.old 157 mgen 13940 [000] 3946.361400: ... 158 159 perf script -i perf.data 160 mgen 13940 [000] 3971.150589 ... 161 162 perf diff --time 3946.361400,:3971.150589, 163 164 It analyzes the perf.data.old from the timestamp 3946.361400 to 165 the end of perf.data.old and analyzes the perf.data from the 166 timestamp 3971.150589 to the end of perf.data. 167 168--cpu:: Only diff samples for the list of CPUs provided. Multiple CPUs can 169 be provided as a comma-separated list with no space: 0,1. Ranges of 170 CPUs are specified with -: 0-2. Default is to report samples on all 171 CPUs. 172 173--pid=:: 174 Only diff samples for given process ID (comma separated list). 175 176--tid=:: 177 Only diff samples for given thread ID (comma separated list). 178 179COMPARISON 180---------- 181The comparison is governed by the baseline file. The baseline perf.data 182file is iterated for samples. All other perf.data files specified on 183the command line are searched for the baseline sample pair. If the pair 184is found, specified computation is made and result is displayed. 185 186All samples from non-baseline perf.data files, that do not match any 187baseline entry, are displayed with empty space within baseline column 188and possible computation results (delta) in their related column. 189 190Example files samples: 191- file A with samples f1, f2, f3, f4, f6 192- file B with samples f2, f4, f5 193- file C with samples f1, f2, f5 194 195Example output: 196 x - computation takes place for pair 197 b - baseline sample percentage 198 199- perf diff A B C 200 201 baseline/A compute/B compute/C samples 202 --------------------------------------- 203 b x f1 204 b x x f2 205 b f3 206 b x f4 207 b f6 208 x x f5 209 210- perf diff B A C 211 212 baseline/B compute/A compute/C samples 213 --------------------------------------- 214 b x x f2 215 b x f4 216 b x f5 217 x x f1 218 x f3 219 x f6 220 221- perf diff C B A 222 223 baseline/C compute/B compute/A samples 224 --------------------------------------- 225 b x f1 226 b x x f2 227 b x f5 228 x f3 229 x x f4 230 x f6 231 232COMPARISON METHODS 233------------------ 234delta 235~~~~~ 236If specified the 'Delta' column is displayed with value 'd' computed as: 237 238 d = A->period_percent - B->period_percent 239 240with: 241 - A/B being matching hist entry from data/baseline file specified 242 (or perf.data/perf.data.old) respectively. 243 244 - period_percent being the % of the hist entry period value within 245 single data file 246 247 - with filtering by -C, -d and/or -S, period_percent might be changed 248 relative to how entries are filtered. Use --percentage=absolute to 249 prevent such fluctuation. 250 251delta-abs 252~~~~~~~~~ 253Same as 'delta` method, but sort the result with the absolute values. 254 255ratio 256~~~~~ 257If specified the 'Ratio' column is displayed with value 'r' computed as: 258 259 r = A->period / B->period 260 261with: 262 - A/B being matching hist entry from data/baseline file specified 263 (or perf.data/perf.data.old) respectively. 264 265 - period being the hist entry period value 266 267wdiff:WEIGHT-B,WEIGHT-A 268~~~~~~~~~~~~~~~~~~~~~~~ 269If specified the 'Weighted diff' column is displayed with value 'd' computed as: 270 271 d = B->period * WEIGHT-A - A->period * WEIGHT-B 272 273 - A/B being matching hist entry from data/baseline file specified 274 (or perf.data/perf.data.old) respectively. 275 276 - period being the hist entry period value 277 278 - WEIGHT-A/WEIGHT-B being user supplied weights in the the '-c' option 279 behind ':' separator like '-c wdiff:1,2'. 280 - WEIGHT-A being the weight of the data file 281 - WEIGHT-B being the weight of the baseline data file 282 283SEE ALSO 284-------- 285linkperf:perf-record[1], linkperf:perf-report[1] 286