Hi Peter,
I can't find a good point of contact for perf, so I'm contacting you based on
the MAINTAINERS file; feel free to redirect somewhere if you're not the right
person.
I'm trying to figure out how to deal with perf report when there are inlined
functions; they don't generally seem to show up in the call stack, which
sometimes can make it very hard to figure out what is going, especially in
a code base one doesn't know too well. As an example, I threw together a
minimal test program:
#include <stdlib.h>
inline int foo()
{
int k = rand();
int sum = 1;
for (int i = 0; i < 10000000000; ++i)
{
sum ^= k;
sum += k;
}
return sum;
}
int main(void)
{
return foo();
}
Compiling with -O2 -g, and running perf record -g yields:
# Samples: 6K of event 'cycles:ppp'
# Event count (approx.): 5876825543
#
# Children Self Command Shared Object Symbol
# ........ ........ ....... ................. ......................
#
99.98% 99.98% inline inline [.] main
|
---0x706258d4c544155
main
99.98% 0.00% inline [unknown] [.] 0x0706258d4c544155
|
---0x706258d4c544155
main
Is there a way I can get it to show “foo” in the call graph? (I suppose also
ideally, “foo” and not “main” should show up in a non-graph run.) Of course,
this gets even more confusing if foo calls bar, since it now looks like the
call chain is main -> bar directly.
I have debug information that should be sufficient in the binary, because if
I break in gdb, I definitely get the call stack:
Program received signal SIGINT, Interrupt.
0x0000555555554589 in foo () at inline.c:5
5 int k = rand();
(gdb) bt
#0 0x0000555555554589 in foo () at inline.c:5
#1 main () at inline.c:17
(gdb)
FWIW, this is with perf from 4.10 (git as of a few days ago) and GCC 6.2.1.
/* Steinar */
--
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