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-f:: 77--force:: 78 Don't complain, do it. 79 80--symfs=<directory>:: 81 Look for files with symbols relative to this directory. 82 83-b:: 84--baseline-only:: 85 Show only items with match in baseline. 86 87-c:: 88--compute:: 89 Differential computation selection - delta,ratio,wdiff (default is delta). 90 See COMPARISON METHODS section for more info. 91 92-p:: 93--period:: 94 Show period values for both compared hist entries. 95 96-F:: 97--formula:: 98 Show formula for given computation. 99 100-o:: 101--order:: 102 Specify compute sorting column number. 103 104--percentage:: 105 Determine how to display the overhead percentage of filtered entries. 106 Filters can be applied by --comms, --dsos and/or --symbols options. 107 108 "relative" means it's relative to filtered entries only so that the 109 sum of shown entries will be always 100%. "absolute" means it retains 110 the original value before and after the filter is applied. 111 112COMPARISON 113---------- 114The comparison is governed by the baseline file. The baseline perf.data 115file is iterated for samples. All other perf.data files specified on 116the command line are searched for the baseline sample pair. If the pair 117is found, specified computation is made and result is displayed. 118 119All samples from non-baseline perf.data files, that do not match any 120baseline entry, are displayed with empty space within baseline column 121and possible computation results (delta) in their related column. 122 123Example files samples: 124- file A with samples f1, f2, f3, f4, f6 125- file B with samples f2, f4, f5 126- file C with samples f1, f2, f5 127 128Example output: 129 x - computation takes place for pair 130 b - baseline sample percentage 131 132- perf diff A B C 133 134 baseline/A compute/B compute/C samples 135 --------------------------------------- 136 b x f1 137 b x x f2 138 b f3 139 b x f4 140 b f6 141 x x f5 142 143- perf diff B A C 144 145 baseline/B compute/A compute/C samples 146 --------------------------------------- 147 b x x f2 148 b x f4 149 b x f5 150 x x f1 151 x f3 152 x f6 153 154- perf diff C B A 155 156 baseline/C compute/B compute/A samples 157 --------------------------------------- 158 b x f1 159 b x x f2 160 b x f5 161 x f3 162 x x f4 163 x f6 164 165COMPARISON METHODS 166------------------ 167delta 168~~~~~ 169If specified the 'Delta' column is displayed with value 'd' computed as: 170 171 d = A->period_percent - B->period_percent 172 173with: 174 - A/B being matching hist entry from data/baseline file specified 175 (or perf.data/perf.data.old) respectively. 176 177 - period_percent being the % of the hist entry period value within 178 single data file 179 180 - with filtering by -C, -d and/or -S, period_percent might be changed 181 relative to how entries are filtered. Use --percentage=absolute to 182 prevent such fluctuation. 183 184ratio 185~~~~~ 186If specified the 'Ratio' column is displayed with value 'r' computed as: 187 188 r = A->period / B->period 189 190with: 191 - A/B being matching hist entry from data/baseline file specified 192 (or perf.data/perf.data.old) respectively. 193 194 - period being the hist entry period value 195 196wdiff:WEIGHT-B,WEIGHT-A 197~~~~~~~~~~~~~~~~~~~~~~~ 198If specified the 'Weighted diff' column is displayed with value 'd' computed as: 199 200 d = B->period * WEIGHT-A - A->period * WEIGHT-B 201 202 - A/B being matching hist entry from data/baseline file specified 203 (or perf.data/perf.data.old) respectively. 204 205 - period being the hist entry period value 206 207 - WEIGHT-A/WEIGHT-B being user supplied weights in the the '-c' option 208 behind ':' separator like '-c wdiff:1,2'. 209 - WEIGHT-A being the weight of the data file 210 - WEIGHT-B being the weight of the baseline data file 211 212SEE ALSO 213-------- 214linkperf:perf-record[1], linkperf:perf-report[1] 215