Profiler

Nodes

A node accumulates the cycles spent between its start and stop calls, and how many times it was stopped. Nodes are defined next to the code they measure and collected at link time in the .pbl_profiler_nodes linker section, sorted by name:

PBL_PROFILER_NODE_DEFINE(compositor);

void compositor_render_app(void) {
  PBL_PROFILER_NODE_START(compositor);
  ...
  PBL_PROFILER_NODE_STOP(compositor);
}

Another file reaches the node with PBL_PROFILER_NODE_DECLARE(). Without CONFIG_PROFILER the node macros compile to nothing, so instrumented code needs no conditionals.

Starting and stopping a node is a syscall: code running unprivileged, such as the application library inside an app, may time nodes too. Calls from unprivileged code with anything but a defined node are ignored.

Runs

pbl_profiler_reset() clears the run and every node, pbl_profiler_start() and pbl_profiler_stop() time the run, and pbl_profiler_print_stats() stops it and logs each node that ran, most cycles first, with its share of the run.

From the shell, profiler start resets and starts a run, and profiler stop stops it and prints the stats.