1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
|
perf-diff(1)
============
NAME
----
perf-diff - Read perf.data files and display the differential profile
SYNOPSIS
--------
[verse]
'perf diff' [baseline file] [data file1] [[data file2] ... ]
DESCRIPTION
-----------
This command displays the performance difference amongst two or more perf.data
files captured via perf record.
If no parameters are passed it will assume perf.data.old and perf.data.
The differential profile is displayed only for events matching both
specified perf.data files.
If no parameters are passed the samples will be sorted by dso and symbol.
As the perf.data files could come from different binaries, the symbols addresses
could vary. So perf diff is based on the comparison of the files and
symbols name.
OPTIONS
-------
-D::
--dump-raw-trace::
Dump raw trace in ASCII.
--kallsyms=<file>::
kallsyms pathname
-m::
--modules::
Load module symbols. WARNING: use only with -k and LIVE kernel
-d::
--dsos=::
Only consider symbols in these dsos. CSV that understands
file://filename entries. This option will affect the percentage
of the Baseline/Delta column. See --percentage for more info.
-C::
--comms=::
Only consider symbols in these comms. CSV that understands
file://filename entries. This option will affect the percentage
of the Baseline/Delta column. See --percentage for more info.
-S::
--symbols=::
Only consider these symbols. CSV that understands
file://filename entries. This option will affect the percentage
of the Baseline/Delta column. See --percentage for more info.
-s::
--sort=::
Sort by key(s): pid, comm, dso, symbol, cpu, parent, srcline.
Please see description of --sort in the perf-report man page.
-t::
--field-separator=::
Use a special separator character and don't pad with spaces, replacing
all occurrences of this separator in symbol names (and other output)
with a '.' character, that thus it's the only non valid separator.
-v::
--verbose::
Be verbose, for instance, show the raw counts in addition to the
diff.
-q::
--quiet::
Do not show any message. (Suppress -v)
-f::
--force::
Don't do ownership validation.
--symfs=<directory>::
Look for files with symbols relative to this directory.
-b::
--baseline-only::
Show only items with match in baseline.
-c::
--compute::
Differential computation selection - delta, ratio, wdiff, cycles,
delta-abs (default is delta-abs). Default can be changed using
diff.compute config option. See COMPARISON METHODS section for
more info.
-p::
--period::
Show period values for both compared hist entries.
-F::
--formula::
Show formula for given computation.
-o::
--order::
Specify compute sorting column number. 0 means sorting by baseline
overhead and 1 (default) means sorting by computed value of column 1
(data from the first file other base baseline). Values more than 1
can be used only if enough data files are provided.
The default value can be set using the diff.order config option.
--percentage::
Determine how to display the overhead percentage of filtered entries.
Filters can be applied by --comms, --dsos and/or --symbols options.
"relative" means it's relative to filtered entries only so that the
sum of shown entries will be always 100%. "absolute" means it retains
the original value before and after the filter is applied.
--time::
Analyze samples within given time window. It supports time
percent with multiple time ranges. Time string is 'a%/n,b%/m,...'
or 'a%-b%,c%-%d,...'.
For example:
Select the second 10% time slice to diff:
perf diff --time 10%/2
Select from 0% to 10% time slice to diff:
perf diff --time 0%-10%
Select the first and the second 10% time slices to diff:
perf diff --time 10%/1,10%/2
Select from 0% to 10% and 30% to 40% slices to diff:
perf diff --time 0%-10%,30%-40%
It also supports analyzing samples within a given time window
<start>,<stop>. Times have the format seconds.nanoseconds. If 'start'
is not given (i.e. time string is ',x.y') then analysis starts at
the beginning of the file. If stop time is not given (i.e. time
string is 'x.y,') then analysis goes to the end of the file.
Multiple ranges can be separated by spaces, which requires the argument
to be quoted e.g. --time "1234.567,1234.789 1235,"
Time string is'a1.b1,c1.d1:a2.b2,c2.d2'. Use ':' to separate timestamps
for different perf.data files.
For example, we get the timestamp information from 'perf script'.
perf script -i perf.data.old
mgen 13940 [000] 3946.361400: ...
perf script -i perf.data
mgen 13940 [000] 3971.150589 ...
perf diff --time 3946.361400,:3971.150589,
It analyzes the perf.data.old from the timestamp 3946.361400 to
the end of perf.data.old and analyzes the perf.data from the
timestamp 3971.150589 to the end of perf.data.
--cpu:: Only diff samples for the list of CPUs provided. Multiple CPUs can
be provided as a comma-separated list with no space: 0,1. Ranges of
CPUs are specified with -: 0-2. Default is to report samples on all
CPUs.
--pid=::
Only diff samples for given process ID (comma separated list).
--tid=::
Only diff samples for given thread ID (comma separated list).
COMPARISON
----------
The comparison is governed by the baseline file. The baseline perf.data
file is iterated for samples. All other perf.data files specified on
the command line are searched for the baseline sample pair. If the pair
is found, specified computation is made and result is displayed.
All samples from non-baseline perf.data files, that do not match any
baseline entry, are displayed with empty space within baseline column
and possible computation results (delta) in their related column.
Example files samples:
- file A with samples f1, f2, f3, f4, f6
- file B with samples f2, f4, f5
- file C with samples f1, f2, f5
Example output:
x - computation takes place for pair
b - baseline sample percentage
- perf diff A B C
baseline/A compute/B compute/C samples
---------------------------------------
b x f1
b x x f2
b f3
b x f4
b f6
x x f5
- perf diff B A C
baseline/B compute/A compute/C samples
---------------------------------------
b x x f2
b x f4
b x f5
x x f1
x f3
x f6
- perf diff C B A
baseline/C compute/B compute/A samples
---------------------------------------
b x f1
b x x f2
b x f5
x f3
x x f4
x f6
COMPARISON METHODS
------------------
delta
~~~~~
If specified the 'Delta' column is displayed with value 'd' computed as:
d = A->period_percent - B->period_percent
with:
- A/B being matching hist entry from data/baseline file specified
(or perf.data/perf.data.old) respectively.
- period_percent being the % of the hist entry period value within
single data file
- with filtering by -C, -d and/or -S, period_percent might be changed
relative to how entries are filtered. Use --percentage=absolute to
prevent such fluctuation.
delta-abs
~~~~~~~~~
Same as 'delta` method, but sort the result with the absolute values.
ratio
~~~~~
If specified the 'Ratio' column is displayed with value 'r' computed as:
r = A->period / B->period
with:
- A/B being matching hist entry from data/baseline file specified
(or perf.data/perf.data.old) respectively.
- period being the hist entry period value
wdiff:WEIGHT-B,WEIGHT-A
~~~~~~~~~~~~~~~~~~~~~~~
If specified the 'Weighted diff' column is displayed with value 'd' computed as:
d = B->period * WEIGHT-A - A->period * WEIGHT-B
- A/B being matching hist entry from data/baseline file specified
(or perf.data/perf.data.old) respectively.
- period being the hist entry period value
- WEIGHT-A/WEIGHT-B being user supplied weights in the the '-c' option
behind ':' separator like '-c wdiff:1,2'.
- WEIGHT-A being the weight of the data file
- WEIGHT-B being the weight of the baseline data file
cycles
~~~~~~
If specified the '[Program Block Range] Cycles Diff' column is displayed.
It displays the cycles difference of same program basic block amongst
two perf.data. The program basic block is the code between two branches.
'[Program Block Range]' indicates the range of a program basic block.
Source line is reported if it can be found otherwise uses symbol+offset
instead.
SEE ALSO
--------
linkperf:perf-record[1], linkperf:perf-report[1]
|
