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This provides a new sysprof-live-unwinder subprocess that runs as root to allow accessing all processes on the system via /proc/$pid/. It is spawned by sysprofd with various perf event FDs and a FD to write captures to. Ideally the capture_fd is something that will naturally error if the client application crashes (such as a socketpair() having the peer close). This is not enforced but encouraged. Additionally, an event_fd is used to allow the client application to signal the live-unwinder to exit. Unwinding is performed by looking at the modules loaded into the target pid and using libdwfl to access DWARF/CFI/etc state machinery. Stack data does not touch the disk as it exists in a mmap buffer from perf and is then translated into a callchain and sent to the Sysprof client. Unwinding occurs as normal post-mortem though is improved through the use of debuginfod to locate the appropriate symbols.
Sysprof is a sampling profiler that uses a kernel module to generate stacktraces which are then interpreted by the userspace program "sysprof".
See the Sysprof homepage for more information.
Merge requests and bug reports should be sent to sysprof's repository on GNOME's GitLab instance. For general discussion and questions, you can create a new topic in GNOME's Discourse.
The former mailing list is archived in https://mail.gnome.org/archives/sysprof-list/.
Debugging symbols
The programs and libraries you want to profile should be compiled
with -fno-omit-frame-pointer and have debugging symbols available,
or you won't get much usable information.
Building Sysprof
You need some packages installed. The package names may vary depending on your distribution, the following command works on Fedora 36:
sudo dnf install gcc gcc-c++ ninja-build gtk4-devel libadwaita-devel
Then do the following:
meson --prefix=/usr build
cd build
ninja
sudo ninja install
WARNING: ninja install will mostly install under the configured install
prefix but installs systemd service configuration directly in the system
default location /usr/lib/systemd so it won't work without root privileges,
even if the install prefix is a user-owned directory.