I said I’d post about gprof, so here goes.
Valgrind and gprof are two very different tools. Valgrind is an instrumenting profiler. Gprof is a sampling profiler. Gprof spends most of its time doing nothing. Then every 100,000,000 clock cycles or so, it looks at the instruction pointer to see what function your program is in. It collects that data enough times to end up with a good idea of where your program is spending its time. The advantage of this approach is that your program runs almost at full speed. This gives you a better idea of how much time your program spends waiting for things like disk or network I/O.
My typical profiling experience with gprof looks like this:
(sets CFLAGS=-pg in Makefile.am)
$ make clean && ./build.sh
(snip)
$ time ./ag --literal abcdefghijklmnopqrstuvwxyz ../ | wc -l
271
real 0m1.144s
user 0m0.792s
sys 0m0.340s
$ gprof -bp ag gmon.out
Flat profile:
Each sample counts as 0.01 seconds.
% cumulative self self total
time seconds seconds calls ms/call ms/call name
36.09 0.22 0.22 20953 0.01 0.01 is_binary
32.81 0.42 0.20 16567 0.01 0.01 boyer_moore_strnstr
13.12 0.50 0.08 63 1.27 1.27 print_file_matches
11.48 0.57 0.07 filename_filter
3.28 0.59 0.02 26377 0.00 0.00 strlcpy
1.64 0.60 0.01 52754 0.00 0.00 strlcat
1.64 0.61 0.01 1 10.01 540.36 search_dir
0.00 0.61 0.00 40160 0.00 0.00 log_debug
0.00 0.61 0.00 40160 0.00 0.00 vplog
0.00 0.61 0.00 213 0.00 0.00 add_ignore_pattern
0.00 0.61 0.00 63 0.00 0.00 print_path
0.00 0.61 0.00 16 0.00 0.00 load_ignore_patterns
0.00 0.61 0.00 1 0.00 0.00 cleanup_ignore_patterns
0.00 0.61 0.00 1 0.00 0.00 generate_skip_lookup
0.00 0.61 0.00 1 0.00 0.00 init_options
0.00 0.61 0.00 1 0.00 0.00 parse_options
0.00 0.61 0.00 1 0.00 0.00 set_log_levelSome caveats: for gprof to work, you need to add -pg to your CFLAGS. Also, gprof is broken on OS X, so run it on a linux server. If you want a sampling profiler on OS X, I recommend Instruments.app.