How do I profile a real world application?

I run Debian 10 and since two weeks or so the PDF reader Atril (a fork of Evince) takes 25 seconds to start. Previously it started almost instantly. Now I'm trying to find out what causes the delay. I have downloaded the source package and built and installed it with profiling enabled: cd "$HOME/.local/src" apt source atril cd atril-1.20.3 ./autogen.sh ./configure CFLAGS=-pg LDFLAGS=-pg --prefix="$HOME/.local" --disable-caja make V=1 make install However, when I launch "$HOME/.local/bin/atril" no file named gmon.out is created. With verbose mode V=1 in the make command I can see that the option -pg is added to compilation and linking commands. Any clues? What's missing? There are several tutorials on the internet showing how to profile simple statically linked example programs but how do we profile "real world" applications? **Edit:** It turned out that gmon.out was created in my home directory. However, when I run Atril through gprof the resulting output doesn't say much because the application is multi-threaded.