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gdbprof

A wall clock time-based profiler powered by GDB and its Python API. Heavily inspired by poor man's profiler.

Rationale

If there's something strange in your neighborhood (like X consuming 75% CPU in memcpy() which perf can't trace), who you gonna call? gdb! Of course, if you're lazy like me, you don't want to spend too much time hitting Ctrl+C.

Caveats

This is hack layered upon hack upon hack. See the source code if you want to know how it "works". With the current state of gdb's Python affairs, it's impossible to do it cleanly, but I think it's slightly better than an expect-based approach because of the lower latency. Use with CAUTION!

Also, I recommend attaching to a running process, rather than starting it from gdb. You'll need to hold down Ctrl+C to stop it if you start it from gdb, as you need to interrupt gdb, not the process (I need to handle this better).

Example

(gdb) source gdbprof.py
(gdb) profile begin
..................................................^C
Profiling complete with 50 samples.
27      poll->None->None->xcb_wait_for_reply->_XReply->None->None->intel_update_renderbuffers->intel_prepare_render->None->None->None->None->None->None->None->None->None->None->None->None->__libc_start_main->None->None->None
10      nanosleep->usleep->None->None->None->None->__libc_start_main->None->None->None
4       poll->None->None->xcb_wait_for_reply->_XReply->None->None->intel_update_renderbuffers->intel_prepare_render->None->None->None->None->__libc_start_main->None->None->None
2       poll->None->None->xcb_wait_for_reply->_XReply->None->None->intel_update_renderbuffers->intel_prepare_render->None->None->None->None->None->None->None->None->None->None->None->None->None->None->__libc_start_main->None->None->None
1       gettimeofday->SDL_GetTicks->None->SDL_PumpEvents->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->__libc_start_main->None->None->None
1       recv->None->None->None->None->_XEventsQueued->XFlush->None->None->SDL_PumpEvents->SDL_PollEvent->None->None->__libc_start_main->None->None->None
1       poll->None->None->xcb_wait_for_reply->_XReply->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->__libc_start_main->None->None->None
1       ioctl->drmIoctl->None->_intel_batchbuffer_flush->intelFinish->None->None->None->None->None->None->__libc_start_main->None->None->None
1       poll->None->None->xcb_wait_for_reply->_XReply->None->None->intel_update_renderbuffers->intel_prepare_render->None->None->None->None->None->None->__libc_start_main->None->None->None
1       None->brw_upload_state->brw_draw_prims->vbo_exec_vtx_flush->None->vbo_exec_FlushVertices->_mesa_PolygonOffset->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->__libc_start_main->None->None->None
1       glDisable->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->None->__libc_start_main->None->None->None
(gdb)