Demonstrations of profile, the Linux eBPF/bcc version. This is a CPU profiler. It works by taking samples of stack traces at timed intervals, and frequency counting them in kernel context for efficiency. Example output: # ./profile Sampling at 49 Hertz of all threads by user + kernel stack... Hit Ctrl-C to end. ^C filemap_map_pages handle_mm_fault __do_page_fault do_page_fault page_fault [unknown] - cp (9036) 1 [unknown] [unknown] - sign-file (8877) 1 __clear_user iov_iter_zero read_iter_zero __vfs_read vfs_read sys_read entry_SYSCALL_64_fastpath read - dd (25036) 4 func_a main __libc_start_main [unknown] - func_ab (13549) 5 The output was long; I truncated some lines ("[...]"). This default output prints stack traces, followed by a line to describe the process (a dash, the process name, and a PID in parenthesis), and then an integer count of how many times this stack trace was sampled. The func_ab process is running the func_a() function, called by main(), called by __libc_start_main(), and called by "[unknown]" with what looks like a bogus address (1st column). That's evidence of a broken stack trace. It's common for user-level software that hasn't been compiled with frame pointers (in this case, libc). The dd process has called read(), and then enters the kernel via entry_SYSCALL_64_fastpath(), calling sys_read(), and so on. Yes, I'm now reading it bottom up. That way follows the code flow. By default, CPU idle stacks are excluded. They can be included with -I: # ./profile -I [...] native_safe_halt default_idle arch_cpu_idle default_idle_call cpu_startup_entry rest_init start_kernel x86_64_start_reservations x86_64_start_kernel - swapper/0 (0) 72 native_safe_halt default_idle arch_cpu_idle default_idle_call cpu_startup_entry start_secondary - swapper/1 (0) 75 The output above shows the most frequent stack was from the "swapper/1" process (PID 0), running the native_safe_halt() function, which was called by default_idle(), which was called by arch_cpu_idle(), and so on. This is the idle thread. Stacks can be read top-down, to follow ancestry: child, parent, grandparent, etc. The dd process profiled ealrier is actually "dd if=/dev/zero of=/dev/null": it's a simple workload to analyze that just moves bytes from /dev/zero to /dev/null. Profiling just that process: # ./profile -p 25036 Sampling at 49 Hertz of PID 25036 by user + kernel stack... Hit Ctrl-C to end. ^C [unknown] [unknown] - dd (25036) 1 __write - dd (25036) 1 read - dd (25036) 1 [...] [unknown] [unknown] - dd (25036) 2 entry_SYSCALL_64_fastpath __write [unknown] - dd (25036) 3 entry_SYSCALL_64_fastpath read - dd (25036) 3 __clear_user iov_iter_zero read_iter_zero __vfs_read vfs_read sys_read entry_SYSCALL_64_fastpath read [unknown] - dd (25036) 3 __clear_user iov_iter_zero read_iter_zero __vfs_read vfs_read sys_read entry_SYSCALL_64_fastpath read - dd (25036) 7 Again, I've truncated some lines. Now we're just analyzing the dd process. The filter is configured by specifying the target PID (from the current PID namespace where we are profiling) via the "-p" flag. Filtering is performed in kernel context, for efficiency, with automatic PID translation to the top-level namespace (if required). This output has some "[unknown]" frames that probably have valid addresses, but we're lacking the symbol translation. This is a common for all profilers on Linux, and is usually fixable. See the DEBUGGING section of the profile(8) man page. You can also profile different process: # ./profile -p 2040,1316151 Sampling at 49 Hertz of PID [2040, 1316151] by user + kernel stack... Hit Ctrl-C to end. ^C PyEval_RestoreThread [unknown] [unknown] - python3 (1316151) 1 [...] rcu_all_qs rcu_all_qs dput step_into handle_dots.part.0 walk_component link_path_walk.part.0 path_openat do_filp_open do_sys_openat2 do_sys_open __x64_sys_openat do_syscall_64 entry_SYSCALL_64_after_hwframe __libc_open64 [unknown] - python3 (2040) 1 Lets add delimiters between the user and kernel stacks, using -d: # ./profile -p 25036 -d ^C __vfs_write sys_write entry_SYSCALL_64_fastpath -- __write - dd (25036) 1 -- [unknown] [unknown] - dd (25036) 1 iov_iter_init __vfs_read vfs_read sys_read entry_SYSCALL_64_fastpath -- read - dd (25036) 1 [...] __clear_user iov_iter_zero read_iter_zero __vfs_read vfs_read sys_read entry_SYSCALL_64_fastpath -- read - dd (25036) 9 In this mode, the delimiters are "--". Here's another example, a func_ab program that runs two functions, func_a() and func_b(). Profiling it for 5 seconds: # ./profile -p `pgrep -n func_ab` 5 Sampling at 49 Hertz of PID 2930 by user + kernel stack for 5 secs. func_a main __libc_start_main [unknown] - func_ab (2930) 2 func_b main __libc_start_main [unknown] - func_ab (2930) 3 func_a main __libc_start_main [unknown] - func_ab (2930) 5 func_b main __libc_start_main [unknown] - func_ab (2930) 12 func_b main __libc_start_main [unknown] - func_ab (2930) 19 func_a main __libc_start_main [unknown] - func_ab (2930) 22 func_b main __libc_start_main [unknown] - func_ab (2930) 64 func_a main __libc_start_main [unknown] - func_ab (2930) 72 Note that the same stack (2nd column) seems to be repeated. Weren't we doing frequency counting and only printing unique stacks? We are, but in terms of the raw addresses, not the symbols. See the 1st column: those stacks are all unique. We can output in "folded format", which puts the stack trace on one line, separating frames with semi-colons. Eg: # ./profile -f -p `pgrep -n func_ab` 5 func_ab;[unknown];__libc_start_main;main;func_a 2 func_ab;[unknown];__libc_start_main;main;func_b 2 func_ab;[unknown];__libc_start_main;main;func_a 11 func_ab;[unknown];__libc_start_main;main;func_b 12 func_ab;[unknown];__libc_start_main;main;func_a 23 func_ab;[unknown];__libc_start_main;main;func_b 28 func_ab;[unknown];__libc_start_main;main;func_b 57 func_ab;[unknown];__libc_start_main;main;func_a 64 I find this pretty useful for writing to files and later grepping. Folded format can also be used by flame graph stack visualizers, including the original implementation: https://github.com/brendangregg/FlameGraph I'd include delimiters, -d. For example: # ./profile -df -p `pgrep -n func_ab` 5 > out.profile # git clone https://github.com/brendangregg/FlameGraph # ./FlameGraph/flamegraph.pl < out.profile > out.svg (Yes, I could pipe profile directly into flamegraph.pl, however, I like to keep the raw folded profiles around: can be useful for regenerating flamegraphs with different options, and, for differential flame graphs.) Some flamegraph.pl palettes recognize kernel annotations, which can be added with -a. It simply adds a "_[k]" at the end of kernel function names. For example: # ./profile -adf -p `pgrep -n dd` 10 dd;[unknown] 1 dd;[unknown];[unknown] 1 dd;[unknown];[unknown] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];__fsnotify_parent_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];__fsnotify_parent_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];__fdget_pos_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];apparmor_file_permission_[k] 1 dd;[unknown] 1 dd;[unknown];[unknown] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;[unknown] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];__fget_light_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];__fsnotify_parent_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];__fget_light_[k] 1 dd;[unknown];[unknown] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k] 1 dd;[unknown];[unknown] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];read_iter_zero_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__fsnotify_parent_[k] 1 dd;[unknown];[unknown] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k];common_file_perm_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];__fsnotify_parent_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];fsnotify_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];security_file_permission_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];__fdget_pos_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k] 1 dd;[unknown];[unknown] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];__fget_light_[k] 1 dd;[unknown] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k] 1 dd;[unknown];[unknown] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];__fsnotify_parent_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];security_file_permission_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k];__clear_user_[k] 1 dd;[unknown];[unknown] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;[unknown];[unknown] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k];common_file_perm_[k] 1 dd;read 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];security_file_permission_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];fsnotify_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];fsnotify_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];apparmor_file_permission_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];__fsnotify_parent_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];apparmor_file_permission_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];iov_iter_init_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];__fsnotify_parent_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];__vfs_write_[k];write_null_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];__clear_user_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];security_file_permission_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k];common_file_perm_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];__fget_light_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];__vfs_read_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];__vfs_write_[k] 1 dd;[unknown] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;[unknown] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];__fsnotify_parent_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;[unknown];[unknown] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;[unknown];__write;-;sys_write_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];__fsnotify_parent_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];common_file_perm_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;[unknown];[unknown] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k];__clear_user_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];__fget_light_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];vfs_read_[k] 1 dd;__write 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];vfs_read_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k];common_file_perm_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];__fget_light_[k] 1 dd;[unknown];[unknown] 1 dd;[unknown] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;[unknown] 1 dd;[unknown] 1 dd;[unknown];[unknown] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k];common_file_perm_[k] 1 dd;__write 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];__fget_light_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k] 1 dd;[unknown] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];__fget_light_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k] 1 dd;[unknown];[unknown] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];__fdget_pos_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];_cond_resched_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];iov_iter_init_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];__fsnotify_parent_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];rw_verify_area_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];apparmor_file_permission_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k] 1 dd;[unknown] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];fsnotify_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];__fdget_pos_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];__vfs_write_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];apparmor_file_permission_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k];common_file_perm_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];__fget_light_[k] 1 dd;[unknown] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];fsnotify_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k];common_file_perm_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];fsnotify_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 1 dd;__write;-;entry_SYSCALL_64_fastpath_[k];vfs_write_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k] 1 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k];common_file_perm_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k] 1 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];fsnotify_[k] 1 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];apparmor_file_permission_[k] 2 dd;read;-;entry_SYSCALL_64_fastpath_[k];__fdget_pos_[k] 2 dd;[unknown];[unknown] 2 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];__fdget_pos_[k] 2 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k];common_file_perm_[k] 2 dd;[unknown];[unknown] 2 dd;[unknown];[unknown] 2 dd;[unknown];[unknown] 2 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k] 2 dd;[unknown];[unknown] 2 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];__clear_user_[k] 2 dd;__write;-;entry_SYSCALL_64_fastpath_[k];__fdget_pos_[k] 2 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k] 2 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k] 2 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k];__clear_user_[k] 2 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k];__clear_user_[k] 2 dd;[unknown];[unknown] 2 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];__fget_light_[k] 2 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];rw_verify_area_[k];security_file_permission_[k];fsnotify_[k] 2 dd;__write;-;sys_write_[k] 2 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];fsnotify_[k] 2 dd;[unknown];[unknown] 2 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k] 2 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 2 dd;read;-;SyS_read_[k] 2 dd;[unknown] 2 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k] 2 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];__fget_light_[k] 2 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k] 2 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k];rw_verify_area_[k];security_file_permission_[k];apparmor_file_permission_[k] 2 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];__clear_user_[k] 2 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];rw_verify_area_[k] 2 dd;[unknown];[unknown] 3 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];rw_verify_area_[k] 3 dd;[unknown];[unknown] 3 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k];__clear_user_[k] 3 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 3 dd;[unknown];[unknown] 3 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 3 dd;[unknown];[unknown] 3 dd;[unknown];[unknown] 3 dd;__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 3 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k] 3 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k];__clear_user_[k] 3 dd;[unknown] 4 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k] 4 dd;[unknown];[unknown] 4 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k] 4 dd;[unknown] 4 dd;[unknown];[unknown] 4 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k] 4 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k];__clear_user_[k] 5 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k];sys_write_[k];vfs_write_[k] 5 dd;[unknown];[unknown] 5 dd;[unknown];[unknown] 5 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k] 6 dd;read 15 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k];__clear_user_[k] 19 dd;[unknown];__write;-;entry_SYSCALL_64_fastpath_[k] 20 dd;read;-;entry_SYSCALL_64_fastpath_[k] 23 dd;read;-;entry_SYSCALL_64_fastpath_[k];SyS_read_[k];vfs_read_[k];__vfs_read_[k];read_iter_zero_[k];iov_iter_zero_[k];__clear_user_[k] 24 dd;__write;-;entry_SYSCALL_64_fastpath_[k] 25 dd;__write 29 dd;[unknown];read;-;entry_SYSCALL_64_fastpath_[k] 31 This can be made into a flamegraph. Eg: # ./profile -adf -p `pgrep -n func_ab` 10 > out.profile # git clone https://github.com/brendangregg/FlameGraph # ./FlameGraph/flamegraph.pl --color=java < out.profile > out.svg It will highlight the kernel frames in orange, and user-level in red (and Java in green, and C++ in yellow). If you copy-n-paste the above output into a out.profile file, you can try it out. You can increase or decrease the sample frequency. Eg, sampling at 9 Hertz: # ./profile -F 9 Sampling at 9 Hertz of all threads by user + kernel stack... Hit Ctrl-C to end. ^C [...] func_b main __libc_start_main [unknown] - func_ab (2930) 1 [...] You can also restrict profiling to just kernel stacks (-K) or user stacks (-U). For example, just user stacks: # ./profile -C 7 2 Sampling at 49 Hertz of all threads by user + kernel stack on CPU#7 for 2 secs. PyEval_EvalFrameEx [unknown] [unknown] - python (2827439) 1 PyDict_GetItem [unknown] - python (2827439) 1 [unknown] - python (2827439) 1 PyEval_EvalFrameEx [unknown] [unknown] - python (2827439) 1 PyEval_EvalFrameEx - python (2827439) 1 [unknown] [unknown] - python (2827439) in this example python application was busylooping on a single core/cpu (#7) we were collecting stack traces only from it # ./profile -U Sampling at 49 Hertz of all threads by user stack... Hit Ctrl-C to end. ^C [unknown] [unknown] - dd (2931) 1 [unknown] [unknown] - dd (2931) 1 [unknown] [unknown] - dd (2931) 1 [unknown] [unknown] - dd (2931) 1 [unknown] [unknown] - dd (2931) 1 func_b main __libc_start_main [unknown] - func_ab (2930) 1 [unknown] - dd (2931) 1 [unknown] - dd (2931) 1 func_a main __libc_start_main [unknown] - func_ab (2930) 3 __write [unknown] - dd (2931) 3 func_a main __libc_start_main [unknown] - func_ab (2930) 4 func_b main __libc_start_main [unknown] - func_ab (2930) 7 - swapper/6 (0) 10 func_b main __libc_start_main [unknown] - func_ab (2930) 10 __write - dd (2931) 10 func_a main __libc_start_main [unknown] - func_ab (2930) 11 read - dd (2931) 12 read [unknown] - dd (2931) 14 If there are too many unique stack traces for the kernel to save, a warning will be printed. Eg: # ./profile [...] WARNING: 8 stack traces could not be displayed. Consider increasing --stack-storage-size. Run ./profile -h to see the default. The --cgroupmap option filters based on a cgroup set. It is meant to be used with an externally created map. # ./profile --cgroupmap /sys/fs/bpf/test01 For more details, see docs/special_filtering.md USAGE message: # ./profile -h usage: profile.py [-h] [-p PID | -L TID] [-U | -K] [-F FREQUENCY | -c COUNT] [-d] [-a] [-I] [-f] [--hash-storage-size HASH_STORAGE_SIZE] [--stack-storage-size STACK_STORAGE_SIZE] [-C CPU] [--cgroupmap CGROUPMAP] [--mntnsmap MNTNSMAP] [duration] Profile CPU stack traces at a timed interval positional arguments: duration duration of trace, in seconds optional arguments: -h, --help show this help message and exit -p PID, --pid PID profile process with one or more comma separated PIDs only -L TID, --tid TID profile thread with one or more comma separated TIDs only -U, --user-stacks-only show stacks from user space only (no kernel space stacks) -K, --kernel-stacks-only show stacks from kernel space only (no user space stacks) -F FREQUENCY, --frequency FREQUENCY sample frequency, Hertz -c COUNT, --count COUNT sample period, number of events -d, --delimited insert delimiter between kernel/user stacks -a, --annotations add _[k] annotations to kernel frames -I, --include-idle include CPU idle stacks -f, --folded output folded format, one line per stack (for flame graphs) --hash-storage-size HASH_STORAGE_SIZE the number of hash keys that can be stored and (default 40960) --stack-storage-size STACK_STORAGE_SIZE the number of unique stack traces that can be stored and displayed (default 16384) -C CPU, --cpu CPU cpu number to run profile on --cgroupmap CGROUPMAP trace cgroups in this BPF map only --mntnsmap MNTNSMAP trace mount namespaces in this BPF map only examples: ./profile # profile stack traces at 49 Hertz until Ctrl-C ./profile -F 99 # profile stack traces at 99 Hertz ./profile -c 1000000 # profile stack traces every 1 in a million events ./profile 5 # profile at 49 Hertz for 5 seconds only ./profile -f 5 # output in folded format for flame graphs ./profile -p 185 # only profile process with PID 185 ./profile -L 185 # only profile thread with TID 185 ./profile -U # only show user space stacks (no kernel) ./profile -K # only show kernel space stacks (no user) ./profile --cgroupmap mappath # only trace cgroups in this BPF map ./profile --mntnsmap mappath # only trace mount namespaces in the map