feat: add profiler util (#5601)

* feat(config): add profiling config settings

- `profile_graphs` enables graph profiling with cProfile
- `profiles_dir` sets the output for profiles

* feat(nodes): add Profiler util

Simple wrapper around cProfile.

* feat(nodes): use Profiler in invocation processor

* scripts: add generate_profile_graphs.sh script

Helper to generate graphs for profiles.

* pkg: add snakeviz and gprof2dot to dev deps

These are useful for profiling.

* tests: add tests for profiler util

* fix(profiler): handle previous profile not stopped cleanly

* feat(profiler): add profile_prefix config setting

The prefix is used when writing profile output files. Useful to organise profiles into sessions.

* tidy(profiler): add `_` to private API

* feat(profiler): simplify API

* feat(profiler): use child logger for profiler logs

* chore(profiler): update docstrings

* feat(profiler): stop() returns output path

* chore(profiler): fix docstring

* tests(profiler): update tests

* chore: ruff

invokeai/app/util/profiler.py

@@ -0,0 +1,67 @@
+import cProfile
+from logging import Logger
+from pathlib import Path
+from typing import Optional
+
+
+class Profiler:
+    """
+    Simple wrapper around cProfile.
+
+    Usage
+    ```
+      # Create a profiler
+      profiler = Profiler(logger, output_dir, "sql_query_perf")
+      # Start a new profile
+      profiler.start("my_profile")
+      # Do stuff
+      profiler.stop()
+    ```
+
+    Visualize a profile as a flamegraph with [snakeviz](https://jiffyclub.github.io/snakeviz/)
+    ```sh
+      snakeviz my_profile.prof
+    ```
+
+    Visualize a profile as directed graph with [graphviz](https://graphviz.org/download/) & [gprof2dot](https://github.com/jrfonseca/gprof2dot)
+    ```sh
+      gprof2dot -f pstats my_profile.prof | dot -Tpng -o my_profile.png
+      # SVG or PDF may be nicer - you can search for function names
+      gprof2dot -f pstats my_profile.prof | dot -Tsvg -o my_profile.svg
+      gprof2dot -f pstats my_profile.prof | dot -Tpdf -o my_profile.pdf
+    ```
+    """
+
+    def __init__(self, logger: Logger, output_dir: Path, prefix: Optional[str] = None) -> None:
+        self._logger = logger.getChild(f"profiler.{prefix}" if prefix else "profiler")
+        self._output_dir = output_dir
+        self._output_dir.mkdir(parents=True, exist_ok=True)
+        self._profiler: Optional[cProfile.Profile] = None
+        self._prefix = prefix
+
+        self.profile_id: Optional[str] = None
+
+    def start(self, profile_id: str) -> None:
+        if self._profiler:
+            self.stop()
+
+        self.profile_id = profile_id
+
+        self._profiler = cProfile.Profile()
+        self._profiler.enable()
+        self._logger.info(f"Started profiling {self.profile_id}.")
+
+    def stop(self) -> Path:
+        if not self._profiler:
+            raise RuntimeError("Profiler not initialized. Call start() first.")
+        self._profiler.disable()
+
+        filename = f"{self._prefix}_{self.profile_id}.prof" if self._prefix else f"{self.profile_id}.prof"
+        path = Path(self._output_dir, filename)
+
+        self._profiler.dump_stats(path)
+        self._logger.info(f"Stopped profiling, profile dumped to {path}.")
+        self._profiler = None
+        self.profile_id = None
+
+        return path