[PATCH v3 00/13] generate full callchain cursor entries for inlined frames

Milian Wolff
2017-09-06T13:55:21Z

This series of patches completely reworks the way inline frames are handled.
Instead of querying for the inline nodes on-demand in the individual tools,
we now create proper callchain nodes for inlined frames. The advantages this
approach brings are numerous:

- less duplicated code in the individual browser
- aggregated cost for inlined frames for the --children top-down list
- various bug fixes that arose from querying for a srcline/symbol based on
the IP of a sample, which will always point to the last inlined frame
instead of the corresponding non-inlined frame
- overall much better support for visualizing cost for heavily-inlined C++
code, which simply was confusing and unreliably before
- srcline honors the global setting as to whether full paths or basenames
should be shown
- caches for inlined frames and srcline information, which allow us to
enable inline frame handling by default

For comparison, below lists the output before and after for `perf script`
and `perf report`. The example file I used to generate the perf data is:

~~~~~
$ cat inlining.cpp
#include <complex>
#include <cmath>
#include <random>
#include <iostream>

using namespace std;

int main()
{
uniform_real_distribution<double> uniform(-1E5, 1E5);
default_random_engine engine;
double s = 0;
for (int i = 0; i < 10000000; ++i) {
s += norm(complex<double>(uniform(engine), uniform(engine)));
}
cout << s << '\n';
return 0;
}
$ g++ -O2 -g -o inlining inlining.cpp
$ perf record --call-graph dwarf ./inlining
~~~~~

Now, the (broken) status-quo looks like this. Look for "NOTE:" to see some
of my comments that outline the various issues I'm trying to solve by this
patch series.

~~~~~
$ perf script --inline
...
inlining 11083 97459.356656: 33680 cycles:
214f7 __hypot_finite (/usr/lib/libm-2.25.so)
ace3 hypot (/usr/lib/libm-2.25.so)
a4a main (/home/milian/projects/src/perf-tests/inlining)
std::__complex_abs
std::abs<double>
std::_Norm_helper<true>::_S_do_it<double>
std::norm<double>
main
20510 __libc_start_main (/usr/lib/libc-2.25.so)
bd9 _start (/home/milian/projects/src/perf-tests/inlining)
# NOTE: the above inlined stack is confusing: the a4a is an address into main,
# which is the non-inlined symbol. the entry with the address should be
# at the end of the stack, where it's actually duplicated once more but
# there it's missing the address
...
$ perf report -s sym -g srcline -i perf.inlining.data --inline --stdio
...
--38.86%--_start
__libc_start_main
|
|--15.68%--main random.tcc:3326
| /home/milian/projects/src/perf-tests/inlining.cpp:14 (inline)
| /usr/include/c++/6.3.1/bits/random.h:1809 (inline)
| /usr/include/c++/6.3.1/bits/random.h:1818 (inline)
| /usr/include/c++/6.3.1/bits/random.h:185 (inline)
| /usr/include/c++/6.3.1/bits/random.tcc:3326 (inline)
|
|--10.36%--main random.h:143
| /home/milian/projects/src/perf-tests/inlining.cpp:14 (inline)
| /usr/include/c++/6.3.1/bits/random.h:1809 (inline)
| /usr/include/c++/6.3.1/bits/random.h:1818 (inline)
| /usr/include/c++/6.3.1/bits/random.h:185 (inline)
| /usr/include/c++/6.3.1/bits/random.tcc:3332 (inline)
| /usr/include/c++/6.3.1/bits/random.h:332 (inline)
| /usr/include/c++/6.3.1/bits/random.h:151 (inline)
| /usr/include/c++/6.3.1/bits/random.h:143 (inline)
|
|--5.66%--main random.tcc:3332
| /home/milian/projects/src/perf-tests/inlining.cpp:14 (inline)
| /usr/include/c++/6.3.1/bits/random.h:1809 (inline)
| /usr/include/c++/6.3.1/bits/random.h:1818 (inline)
| /usr/include/c++/6.3.1/bits/random.h:185 (inline)
| /usr/include/c++/6.3.1/bits/random.tcc:3332 (inline)
...
# NOTE: the grouping is totally off because the first and last frame of the
inline nodes is completely bogus, since the IP is used to find the sym/srcline
which is different from the actual inlined sym/srcline.
also, the code currently displays either the inlined function name or
the corresponding filename (but in full length, instead of just the basename).

$ perf report -s sym -g srcline -i perf.inlining.data --inline --stdio --no-children
...
38.86% [.] main
|
|--15.68%--main random.tcc:3326
| /usr/include/c++/6.3.1/bits/random.tcc:3326 (inline)
| /usr/include/c++/6.3.1/bits/random.h:185 (inline)
| /usr/include/c++/6.3.1/bits/random.h:1818 (inline)
| /usr/include/c++/6.3.1/bits/random.h:1809 (inline)
| /home/milian/projects/src/perf-tests/inlining.cpp:14 (inline)
| __libc_start_main
| _start
...
# NOTE: the srcline for main is wrong, it should be inlining.cpp:14,
i.e. what is displayed in the line below (see also perf script issue above)
~~~~~

Afterwards, all of the above issues are resolved (and inlined frames are
displayed by default):

~~~~~
$ perf script
...
inlining 11083 97459.356656: 33680 cycles:
214f7 __hypot_finite (/usr/lib/libm-2.25.so)
ace3 hypot (/usr/lib/libm-2.25.so)
a4a std::__complex_abs (inlined)
a4a std::abs<double> (inlined)
a4a std::_Norm_helper<true>::_S_do_it<double> (inlined)
a4a std::norm<double> (inlined)
a4a main (/home/milian/projects/src/perf-tests/inlining)
20510 __libc_start_main (/usr/lib/libc-2.25.so)
bd9 _start (/home/milian/projects/src/perf-tests/inlining)
...
# NOTE: only one main entry, at the correct position.
we do display the (repeated) instruction pointer as that ensures
interoperability with e.g. the stackcollapse-perf.pl script

$ perf report -s sym -g srcline -i perf.inlining.data --stdio
...
100.00% 38.86% [.] main
|
|--61.14%--main inlining.cpp:14
| std::norm<double> complex:664 (inlined)
| std::_Norm_helper<true>::_S_do_it<double> complex:654 (inlined)
| std::abs<double> complex:597 (inlined)
| std::__complex_abs complex:589 (inlined)
| |
| |--60.29%--hypot
| | |
| | --56.03%--__hypot_finite
| |
| --0.85%--cabs
|
--38.86%--_start
__libc_start_main
|
|--38.19%--main inlining.cpp:14
| |
| |--35.59%--std::uniform_real_distribution<double>::operator()<std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul> > random.h:1809 (inlined)
| | std::uniform_real_distribution<double>::operator()<std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul> > random.h:1818 (inlined)
| | |
| | --34.37%--std::__detail::_Adaptor<std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul>, double>::operator() random.h:185 (inlined)
| | |
| | |--17.91%--std::generate_canonical<double, 53ul, std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul> > random.tcc:3332 (inlined)
| | | |
| | | --12.24%--std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul>::operator() random.h:332 (inlined)
| | | std::__detail::__mod<unsigned long, 2147483647ul, 16807ul, 0ul> random.h:151 (inlined)
| | | |
| | | |--10.36%--std::__detail::_Mod<unsigned long, 2147483647ul, 16807ul, 0ul, true, true>::__calc random.h:143 (inlined)
| | | |
| | | --1.88%--std::__detail::_Mod<unsigned long, 2147483647ul, 16807ul, 0ul, true, true>::__calc random.h:141 (inlined)
| | |
| | |--15.68%--std::generate_canonical<double, 53ul, std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul> > random.tcc:3326 (inlined)
| | |
| | --0.79%--std::generate_canonical<double, 53ul, std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul> > random.tcc:3335 (inlined)
| |
| --1.99%--std::norm<double> complex:664 (inlined)
| std::_Norm_helper<true>::_S_do_it<double> complex:654 (inlined)
| std::abs<double> complex:597 (inlined)
| std::__complex_abs complex:589 (inlined)
|
--0.67%--main inlining.cpp:13
...

# NOTE: still somewhat confusing due to the _start and __libc_start_main frames
that actually are *above* the main frame. But at least the stuff below
properly splits up and shows that mutiple functions got inlined into
inlining.cpp:14, not just one as before.

$ perf report -s sym -g srcline -i perf.inlining.data --stdio --no-children
...
38.86% [.] main
|
|--15.68%--std::generate_canonical<double, 53ul, std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul> > random.tcc:3326 (inlined)
| std::__detail::_Adaptor<std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul>, double>::operator() random.h:185 (inlined)
| std::uniform_real_distribution<double>::operator()<std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul> > random.h:1818 (inlined)
| std::uniform_real_distribution<double>::operator()<std::linear_congruential_engine<unsigned long, 16807ul, 0ul, 2147483647ul> > random.h:1809 (inlined)
| main inlining.cpp:14
| __libc_start_main
| _start
...
# NOTE: the first and last entry of the inline stack have the correct symbol and srcline now
both function and srcline is shown, as well as the (inlined) suffix
only the basename of the srcline is shown

v3 splits the initial patch up into two to simplify reviewing. It also adds a
comment to clarify the lifetime handling of fake symbols and aliased non-fake
symbols, based on the feedback by Namhyung.

v2 fixes some issues reported by Namhyung or found by me in further
testing, adds caching and enables inline frames by default.

Milian Wolff (13):
perf report: remove code to handle inline frames from browsers
perf util: store srcline in callchain_cursor_node
perf report: create real callchain entries for inlined frames
perf report: fall-back to function name comparison for -g srcline
perf report: mark inlined frames in output by " (inlined)" suffix
perf script: mark inlined frames and do not print DSO for them
perf report: compare symbol name for inlined frames when matching
perf report: compare symbol name for inlined frames when sorting
perf report: properly handle branch count in match_chain
perf report: cache failed lookups of inlined frames
perf report: cache srclines for callchain nodes
perf report: use srcline from callchain for hist entries
perf util: enable handling of inlined frames by default

tools/perf/Documentation/perf-report.txt | 3 +-
tools/perf/Documentation/perf-script.txt | 3 +-
tools/perf/ui/browsers/hists.c | 180 ++-------------------
tools/perf/ui/stdio/hist.c | 77 +--------
tools/perf/util/callchain.c | 151 ++++++++---------
tools/perf/util/callchain.h | 6 +-
tools/perf/util/dso.c | 3 +
tools/perf/util/dso.h | 2 +
tools/perf/util/event.c | 1 +
tools/perf/util/evsel_fprintf.c | 37 +----
tools/perf/util/hist.c | 7 +-
tools/perf/util/machine.c | 65 +++++++-
tools/perf/util/sort.c | 6 +
tools/perf/util/sort.h | 1 -
tools/perf/util/srcline.c | 268 ++++++++++++++++++++++++-------
tools/perf/util/srcline.h | 26 ++-
tools/perf/util/symbol.c | 1 +
tools/perf/util/symbol.h | 2 +
18 files changed, 419 insertions(+), 420 deletions(-)

--
2.14.1