table of contents
PERF-DIFF(1) | perf Manual | PERF-DIFF(1) |
NAME¶
perf-diff - Read perf.data files and display the differential profile
SYNOPSIS¶
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
--kallsyms=<file>
-m, --modules
-d, --dsos=
-C, --comms=
-S, --symbols=
-s, --sort=
-t, --field-separator=
-v, --verbose
-q, --quiet
-f, --force
--symfs=<directory>
-b, --baseline-only
-c, --compute
--cycles-hist
-p, --period
-F, --formula
-o, --order
--percentage
"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
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
--pid=
--tid=
--stream
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
baseline/A compute/B compute/C samples --------------------------------------- b x f1 b x x f2 b f3 b x f4 b f6
x x f5
baseline/B compute/A compute/C samples --------------------------------------- b x x f2 b x f4 b x f5
x x f1
x f3
x f6
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.
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.
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
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¶
06/14/2024 | perf |