6 perf-diff - Read perf.data files and display the differential profile
11 'perf diff' [baseline file] [data file1] [[data file2] ... ]
15 This command displays the performance difference amongst two or more perf.data
16 files captured via perf record.
18 If no parameters are passed it will assume perf.data.old and perf.data.
20 The differential profile is displayed only for events matching both
21 specified perf.data files.
23 If no parameters are passed the samples will be sorted by dso and symbol.
24 As the perf.data files could come from different binaries, the symbols addresses
25 could vary. So perf diff is based on the comparison of the files and
32 Dump raw trace in ASCII.
39 Load module symbols. WARNING: use only with -k and LIVE kernel
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.
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.
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.
61 Sort by key(s): pid, comm, dso, symbol, cpu, parent, srcline.
62 Please see description of --sort in the perf-report man page.
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.
73 Be verbose, for instance, show the raw counts in addition to the
78 Don't do ownership validation.
81 Look for files with symbols relative to this directory.
85 Show only items with match in baseline.
89 Differential computation selection - delta, ratio, wdiff, delta-abs
90 (default is delta-abs). Default can be changed using diff.compute
91 config option. See COMPARISON METHODS section for more info.
95 Show period values for both compared hist entries.
99 Show formula for given computation.
103 Specify compute sorting column number. 0 means sorting by baseline
104 overhead and 1 (default) means sorting by computed value of column 1
105 (data from the first file other base baseline). Values more than 1
106 can be used only if enough data files are provided.
107 The default value can be set using the diff.order config option.
110 Determine how to display the overhead percentage of filtered entries.
111 Filters can be applied by --comms, --dsos and/or --symbols options.
113 "relative" means it's relative to filtered entries only so that the
114 sum of shown entries will be always 100%. "absolute" means it retains
115 the original value before and after the filter is applied.
119 The comparison is governed by the baseline file. The baseline perf.data
120 file is iterated for samples. All other perf.data files specified on
121 the command line are searched for the baseline sample pair. If the pair
122 is found, specified computation is made and result is displayed.
124 All samples from non-baseline perf.data files, that do not match any
125 baseline entry, are displayed with empty space within baseline column
126 and possible computation results (delta) in their related column.
128 Example files samples:
129 - file A with samples f1, f2, f3, f4, f6
130 - file B with samples f2, f4, f5
131 - file C with samples f1, f2, f5
134 x - computation takes place for pair
135 b - baseline sample percentage
139 baseline/A compute/B compute/C samples
140 ---------------------------------------
150 baseline/B compute/A compute/C samples
151 ---------------------------------------
161 baseline/C compute/B compute/A samples
162 ---------------------------------------
174 If specified the 'Delta' column is displayed with value 'd' computed as:
176 d = A->period_percent - B->period_percent
179 - A/B being matching hist entry from data/baseline file specified
180 (or perf.data/perf.data.old) respectively.
182 - period_percent being the % of the hist entry period value within
185 - with filtering by -C, -d and/or -S, period_percent might be changed
186 relative to how entries are filtered. Use --percentage=absolute to
187 prevent such fluctuation.
191 Same as 'delta` method, but sort the result with the absolute values.
195 If specified the 'Ratio' column is displayed with value 'r' computed as:
197 r = A->period / B->period
200 - A/B being matching hist entry from data/baseline file specified
201 (or perf.data/perf.data.old) respectively.
203 - period being the hist entry period value
205 wdiff:WEIGHT-B,WEIGHT-A
206 ~~~~~~~~~~~~~~~~~~~~~~~
207 If specified the 'Weighted diff' column is displayed with value 'd' computed as:
209 d = B->period * WEIGHT-A - A->period * WEIGHT-B
211 - A/B being matching hist entry from data/baseline file specified
212 (or perf.data/perf.data.old) respectively.
214 - period being the hist entry period value
216 - WEIGHT-A/WEIGHT-B being user supplied weights in the the '-c' option
217 behind ':' separator like '-c wdiff:1,2'.
218 - WEIGHT-A being the weight of the data file
219 - WEIGHT-B being the weight of the baseline data file
223 linkperf:perf-record[1], linkperf:perf-report[1]