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
23OPTIONS
24-------
25-D::
26--dump-raw-trace::
27        Dump raw trace in ASCII.
28
29-m::
30--modules::
31        Load module symbols. WARNING: use only with -k and LIVE kernel
32
33-d::
34--dsos=::
35	Only consider symbols in these dsos. CSV that understands
36	file://filename entries.  This option will affect the percentage
37	of the Baseline/Delta column.  See --percentage for more info.
38
39-C::
40--comms=::
41	Only consider symbols in these comms. CSV that understands
42	file://filename entries.  This option will affect the percentage
43	of the Baseline/Delta column.  See --percentage for more info.
44
45-S::
46--symbols=::
47	Only consider these symbols. CSV that understands
48	file://filename entries.  This option will affect the percentage
49	of the Baseline/Delta column.  See --percentage for more info.
50
51-s::
52--sort=::
53	Sort by key(s): pid, comm, dso, symbol, cpu, parent, srcline.
54	Please see description of --sort in the perf-report man page.
55
56-t::
57--field-separator=::
58
59	Use a special separator character and don't pad with spaces, replacing
60	all occurrences of this separator in symbol names (and other output)
61	with a '.' character, that thus it's the only non valid separator.
62
63-v::
64--verbose::
65	Be verbose, for instance, show the raw counts in addition to the
66	diff.
67
68-f::
69--force::
70       Don't complain, do it.
71
72--symfs=<directory>::
73        Look for files with symbols relative to this directory.
74
75-b::
76--baseline-only::
77        Show only items with match in baseline.
78
79-c::
80--compute::
81        Differential computation selection - delta,ratio,wdiff (default is delta).
82        See COMPARISON METHODS section for more info.
83
84-p::
85--period::
86        Show period values for both compared hist entries.
87
88-F::
89--formula::
90        Show formula for given computation.
91
92-o::
93--order::
94       Specify compute sorting column number.
95
96--percentage::
97	Determine how to display the overhead percentage of filtered entries.
98	Filters can be applied by --comms, --dsos and/or --symbols options.
99
100	"relative" means it's relative to filtered entries only so that the
101	sum of shown entries will be always 100%.  "absolute" means it retains
102	the original value before and after the filter is applied.
103
104COMPARISON
105----------
106The comparison is governed by the baseline file. The baseline perf.data
107file is iterated for samples. All other perf.data files specified on
108the command line are searched for the baseline sample pair. If the pair
109is found, specified computation is made and result is displayed.
110
111All samples from non-baseline perf.data files, that do not match any
112baseline entry, are displayed with empty space within baseline column
113and possible computation results (delta) in their related column.
114
115Example files samples:
116- file A with samples f1, f2, f3, f4,    f6
117- file B with samples     f2,     f4, f5
118- file C with samples f1, f2,         f5
119
120Example output:
121  x - computation takes place for pair
122  b - baseline sample percentage
123
124- perf diff A B C
125
126  baseline/A compute/B compute/C  samples
127  ---------------------------------------
128  b                    x          f1
129  b          x         x          f2
130  b                               f3
131  b          x                    f4
132  b                               f6
133             x         x          f5
134
135- perf diff B A C
136
137  baseline/B compute/A compute/C  samples
138  ---------------------------------------
139  b          x         x          f2
140  b          x                    f4
141  b                    x          f5
142             x         x          f1
143             x                    f3
144             x                    f6
145
146- perf diff C B A
147
148  baseline/C compute/B compute/A  samples
149  ---------------------------------------
150  b                    x          f1
151  b          x         x          f2
152  b          x                    f5
153                       x          f3
154             x         x          f4
155                       x          f6
156
157COMPARISON METHODS
158------------------
159delta
160~~~~~
161If specified the 'Delta' column is displayed with value 'd' computed as:
162
163  d = A->period_percent - B->period_percent
164
165with:
166  - A/B being matching hist entry from data/baseline file specified
167    (or perf.data/perf.data.old) respectively.
168
169  - period_percent being the % of the hist entry period value within
170    single data file
171
172  - with filtering by -C, -d and/or -S, period_percent might be changed
173    relative to how entries are filtered.  Use --percentage=absolute to
174    prevent such fluctuation.
175
176ratio
177~~~~~
178If specified the 'Ratio' column is displayed with value 'r' computed as:
179
180  r = A->period / B->period
181
182with:
183  - A/B being matching hist entry from data/baseline file specified
184    (or perf.data/perf.data.old) respectively.
185
186  - period being the hist entry period value
187
188wdiff:WEIGHT-B,WEIGHT-A
189~~~~~~~~~~~~~~~~~~~~~~~
190If specified the 'Weighted diff' column is displayed with value 'd' computed as:
191
192   d = B->period * WEIGHT-A - A->period * WEIGHT-B
193
194  - A/B being matching hist entry from data/baseline file specified
195    (or perf.data/perf.data.old) respectively.
196
197  - period being the hist entry period value
198
199  - WEIGHT-A/WEIGHT-B being user suplied weights in the the '-c' option
200    behind ':' separator like '-c wdiff:1,2'.
201    - WIEGHT-A being the weight of the data file
202    - WIEGHT-B being the weight of the baseline data file
203
204SEE ALSO
205--------
206linkperf:perf-record[1], linkperf:perf-report[1]
207