perf(images): run image work on two own pools and trim after jobs (#523) (#582)

* perf(images): read PNG text without decoding pixels (#523)

Pillow's PngImageFile.text loads every pixel to reach text chunks written
after IDAT. The scan's metadata batch and the image monitor now read PNG
text through utils/png_text.py, which runs Pillow's own chunk handlers
after the first IDAT and seeks over the pixel data.

The legacy .text read is the floor: a differential test compares both
readers on every fixture image, a curated corpus and a seeded fuzz. The
only difference is a file whose pixel data is undecodable or cut short:
it now keeps the text read before its pixels instead of reading nothing.
Animated PNGs still use .text.

* test(images): cover the text budget, XMP and layout guard of the PNG text walk (#523)

* perf(images): run image work on two own pools and trim after jobs (#523)

Image work no longer spreads over the default executor's threads, where
glibc kept an image-sized malloc arena per thread.

- Interactive image work (view previews behind their gate, workspace card
  facts, both inspector routes) runs on the API's fixed pm-image pool of
  3 threads; the on-demand preview pool is merged into it.
- map_parallel (scan metadata, thumbnail and convert jobs, the legacy
  gallery generation, capture previews) shares one long-lived pm-worker
  pool of Worker threads, reused between jobs. The package teardown stops
  it within its bound (part "workers").
- After a scan, thumbnail or convert job, glibc's malloc_trim(0) returns
  free pages once; a no-op on Windows, macOS and musl.
- tools/perf/memory_drive.py measures RSS, heap, threads and arenas under
  the #523 load on the disposable browser test server (manual only).

* fix(images): start no image thread after the teardown; join retired job pools (#523)

py/api/__init__.py

@@ -85,6 +85,7 @@ try:
     from ...database.operations import PromptDatabase
     from ...utils.file_prompt import parse_comfyui_prompt
     from ...utils.logging_config import get_logger
+    from ...utils.native_memory import release_free_memory
     from ...utils.png_text import png_text
     from ...utils.video_metadata import is_video_path, read_video_metadata
 except ImportError:
@@ -96,6 +97,7 @@ except ImportError:
     from database.operations import PromptDatabase
     from utils.file_prompt import parse_comfyui_prompt
     from utils.logging_config import get_logger
+    from utils.native_memory import release_free_memory
     from utils.png_text import png_text
     from utils.video_metadata import is_video_path, read_video_metadata
 
@@ -528,6 +530,14 @@ class PromptManagerAPI(
             return await loop.run_in_executor(None, call)
         return await loop.run_in_executor(None, func, *args)
 
+    async def _release_job_memory(self):
+        """After a scan or thumbnail job: glibc's free heap pages go back to
+        the OS once (``malloc_trim(0)``; nothing elsewhere, #523)."""
+        try:
+            await self._run_in_executor(release_free_memory)
+        except Exception:  # best effort: the job's result already stands
+            self.logger.debug("Releasing free memory failed", exc_info=True)
+
     def _root_listing(self, root) -> RootListing:
         """The shared listing record of one output root (created empty)."""
         return self._root_listings.setdefault(str(root), RootListing())

py/api/admin.py

@@ -1454,6 +1454,7 @@ class AdminRoutesMixin:
             verb = "cancelled" if state == "cancelled" else "finished"
             job.log_line(f"Scan {verb} · {_plural(job.processed, 'file')} processed")
         job.finish(state)
+        await self._release_job_memory()
         if state == "finished":
             # After the scan, so the guarded thumbnail job is admitted (#249).
             await self._hand_off_scan_thumbnails(job, output_dirs)
@@ -1668,7 +1669,8 @@ class AdminRoutesMixin:
     def _extract_batch_metadata_sync(self, file_batch):
         """Extract metadata from a batch of files in one executor call.
 
-        Files are read on ``PromptManagerConfig.WORKER_THREADS`` threads.
+        Files are read on the long-lived job pool of
+        ``PromptManagerConfig.WORKER_THREADS`` threads (#523).
         PNG text is read chunk by chunk without decoding pixels (#523); file
         reads and ffprobe release the GIL.
         """

py/api/history.py

@@ -843,7 +843,10 @@ class HistoryRoutesMixin:
                 raise
 
         async def execute():
-            pending = asyncio.create_task(self._run_in_executor(project))
+            # An inspection reads the file's header and text: the
+            # interactive image pool (#523); media stays on the default.
+            run = self._run_image if kind == "inspection" else self._run_in_executor
+            pending = asyncio.create_task(run(project))
             try:
                 return await asyncio.shield(pending)
             except asyncio.CancelledError:

py/api/images.py

@@ -2975,6 +2975,7 @@ class ImageRoutesMixin:
             result = await self._run_in_executor(
                 self._generate_gallery_thumbnails_sync, output_dirs
             )
+            await self._release_job_memory()
             return web.json_response(result)
 
         except Exception as e:
@@ -3997,7 +3998,8 @@ class ImageRoutesMixin:
                     **observed,
                 )
 
-            body = await self._run_in_executor(inspect)
+            # Header and text reads: the interactive image pool (#523).
+            body = await self._run_image(inspect)
             if body is None:
                 return web.json_response(
                     {
@@ -4210,6 +4212,22 @@ class ImageRoutesMixin:
         # (which Windows refuses on open files) is not held up by it.
         return _CardFacts(width, height, *self._card_parse(path, records))
 
+    def _cached_card_facts(self, entry: tuple) -> _CardFacts | None:
+        path, mtime, root, index = entry[:4]
+        return self._workspace_card_cache.get((index, str(root)), {}).get((path, mtime))
+
+    def _card_facts_of(self, entries: list, *, parse: bool) -> list[_CardFacts]:
+        """Card facts of *entries*, in order; files not cached yet are read on
+        the interactive image pool (#523), cached ones answer here."""
+        found = [self._cached_card_facts(entry) for entry in entries]
+        missing = [i for i, facts in enumerate(found) if facts is None]
+        read = self._map_image(
+            lambda i: self._card_facts(entries[i], parse=parse), missing
+        )
+        for i, facts in zip(missing, read):
+            found[i] = facts
+        return found
+
     def _card_facts(self, entry: tuple, *, parse: bool) -> _CardFacts:
         """One listed image's card facts, read once per ``(path, mtime)``.
 
@@ -4218,11 +4236,11 @@ class ImageRoutesMixin:
         and drops the rest, and a roots change drops them all. Only files of
         the current scan are stored, so the cache is bounded by the listing.
         """
-        path, mtime, root, index = entry[:4]
-        root_key, key = (index, str(root)), (path, mtime)
-        cached = self._workspace_card_cache.get(root_key, {}).get(key)
+        cached = self._cached_card_facts(entry)
         if cached is not None:
             return cached
+        path, mtime, root, index = entry[:4]
+        root_key, key = (index, str(root)), (path, mtime)
         facts = self._read_card_facts(path, parse=parse)
         if facts is None:
             # Not stored: a locked or half-written file may read next time.
@@ -4248,15 +4266,17 @@ class ImageRoutesMixin:
             if linked
             else {}
         )
+        # Videos: the card reads no video metadata. Library previews show
+        # no card facts, so they skip the parse (``parse=linked``).
+        stills = [image for image in images if not image["is_video"]]
+        read = self._card_facts_of(
+            [entries[(image["root_index"], image["path"])] for image in stills],
+            parse=linked,
+        )
+        facts_of = {id(image): facts for image, facts in zip(stills, read)}
         for image in images:
             entry = entries[(image["root_index"], image["path"])]
-            # Videos: the card reads no video metadata. Library previews show
-            # no card facts, so they skip the parse (``parse=linked``).
-            facts = (
-                _NO_CARD_FACTS
-                if image["is_video"]
-                else self._card_facts(entry, parse=linked)
-            )
+            facts = facts_of.get(id(image), _NO_CARD_FACTS)
             image["width"], image["height"] = facts.width, facts.height
             if not linked:
                 continue

py/api/thumbnail_auto.py

@@ -8,7 +8,8 @@ previews behind those URLs are made here, in three ways:
 - **On first view.** ``GET /prompt_manager/images/serve/thumbnails/<rel>_thumb
   <ext>`` for a preview that does not exist yet is admitted on the event loop
   (``_PreviewGate``): at most ``ON_DEMAND_LIMIT`` previews are written at once,
-  on this API's own small pool (never the default executor), one flight runs
+  on this API's interactive image pool (``IMAGE_POOL_SIZE`` threads, shared
+  with card facts and inspector reads; never the default executor), one flight runs
   per file, and the requests waiting are capped (``MAX_WAITING``); past the
   cap a request gets its fallback at once. Inside the admission the preview is
   mapped back to its media file under the same root (the request text is
@@ -24,7 +25,8 @@ previews behind those URLs are made here, in three ways:
 - **On capture.** The image monitor hands every new output it settles to
   ``queue_capture_thumbnail``, which queues its preview for one background
   worker thread (``AutoThumbnailer``). Each wake takes at most Worker threads
-  (``WORKER_THREADS``) files and writes them on that many threads; enqueuing
+  (``WORKER_THREADS``) files and writes them on the long-lived job pool
+  (``utils.parallel``, shared with scans and thumbnail jobs); enqueuing
   is O(1), so the monitor and ComfyUI's queue never wait. A file already
   queued is not queued again, the queue is bounded (``MAX_QUEUED``) and a
   preview left out is made on its first view instead.
@@ -49,7 +51,7 @@ write starts (after its slot) and again just before its rename.
 
 Shutdown: ``close_auto_thumbnails`` stops the worker at a file boundary,
 kills a running ffmpeg, waits a bounded time (and logs when the wait ran
-out) and shuts the view pool down; after the app's cleanup
+out) and shuts the image pool down; after the app's cleanup
 (``final=True``) nothing starts a worker again. Importing this module again
 (a package reload) stops the workers the previous import left.
 """
@@ -60,7 +62,7 @@ import functools
 import io
 import os
 import threading
-from concurrent.futures import ThreadPoolExecutor
+from concurrent.futures import CancelledError, ThreadPoolExecutor
 from pathlib import Path
 
 from aiohttp import web
@@ -104,8 +106,11 @@ PLACEHOLDER_SIZE = (thumbnail_settings.DEFAULT_EDGE, thumbnail_settings.DEFAULT_
 PLACEHOLDER_QUALITY = 85
 # Source extensions in the order a shared preview name looks for them (R2).
 _SOURCE_ORDER = thumbnail_settings.IMAGE_SOURCE_ORDER + tuple(sorted(VIDEO_EXTENSIONS))
-# Previews views may write at once (the size of the view pool).
-ON_DEMAND_LIMIT = 3
+# Threads of the interactive image pool (#523): view previews, card facts and
+# inspector reads. Fixed, so image buffers stay in a few threads' arenas.
+IMAGE_POOL_SIZE = 3
+# Previews views may write at once (the whole image pool).
+ON_DEMAND_LIMIT = IMAGE_POOL_SIZE
 # View requests that may wait on the gate; one more gets its fallback at once.
 MAX_WAITING = 64
 # How long a pool thread waits for the capture worker's flight of the same file.
@@ -124,7 +129,7 @@ AUTO_REFUSED_KINDS = frozenset(
     {RESTORE_JOB_KIND, DUPLICATE_CLEANUP_JOB_KIND, SOURCE_CHANGE_JOB_KIND}
 )
 WORKER_NAME = "PromptManagerThumbnailWorker"
-POOL_PREFIX = "pm-preview"
+POOL_PREFIX = "pm-image"
 # Identifies this import's workers: a reload stops the ones it did not start.
 _MODULE_TOKEN = object()
 
@@ -294,7 +299,7 @@ class AutoThumbnailer:
     ``generate(src, dst, is_video, *, stop, guard, track)`` writes one
     preview and returns ``_generate_one``'s result dict; ``may_write()``
     says whether automatic previews may be written now. Views call
-    ``ensure`` on the view pool, the monitor calls ``enqueue`` from its
+    ``ensure`` on the image pool, the monitor calls ``enqueue`` from its
     thread.
     """
 
@@ -491,12 +496,15 @@ class AutoThumbnailer:
                     self._worker_running = False
                     self._changed.notify_all()
                     return
-                take = min(len(self._queue), max(1, int(self._workers() or 1)))
+                workers = max(1, int(self._workers() or 1))
+                take = min(len(self._queue), workers)
                 batch = [self._queue.popleft() for _ in range(take)]
                 self._batch = len(batch)
                 self._changed.notify_all()
             try:
-                map_parallel(self._write_queued, batch, len(batch))
+                # The job pool's size is the setting; a smaller batch uses
+                # fewer of its threads (#523: one long-lived pool).
+                map_parallel(self._write_queued, batch, workers)
             finally:
                 with self._changed:
                     self._batch = 0
@@ -567,7 +575,7 @@ class _PreviewGate:
     """Admission of view requests on the event loop (#249 I2).
 
     Waiters are coroutines: at most ``limit`` previews are written at once
-    on the view pool, one flight runs per key, and past ``MAX_WAITING``
+    on the image pool, one flight runs per key, and past ``MAX_WAITING``
     waiting requests ``run`` answers ``OVER`` at once.
     """
 
@@ -622,13 +630,17 @@ class _PreviewGate:
                 flight.set_result(result)
 
 
+def _on_image_thread():
+    return threading.current_thread().name.startswith(POOL_PREFIX + "_")
+
+
 class AutoThumbnailMixin:
     """Automatic previews on the API: views, the monitor's queue, scans."""
 
     _auto_thumbnailer = None
     _auto_thumbnails_shut = False
     _preview_gate_obj = None
-    _preview_pool_obj = None
+    _image_pool_obj = None
     _auto_thumbnailer_lock = threading.Lock()
 
     def _auto_thumbnails(self):
@@ -651,7 +663,7 @@ class AutoThumbnailMixin:
             self._auto_thumbnails_shut = True
 
     def close_auto_thumbnails(self, final=False, timeout=None):
-        """Stop the capture worker and the view pool, and forget them.
+        """Stop the capture worker and the image pool, and forget them.
 
         Bounded by ``timeout`` (see AutoThumbnailer.close). ``final`` (the
         package teardown) also keeps a late monitor event from starting a
@@ -662,7 +674,7 @@ class AutoThumbnailMixin:
             if final:
                 self._auto_thumbnails_shut = True
             thumbnailer, self._auto_thumbnailer = self._auto_thumbnailer, None
-            pool, self._preview_pool_obj = self._preview_pool_obj, None
+            pool, self._image_pool_obj = self._image_pool_obj, None
             self._preview_gate_obj = None
         closed = True
         if thumbnailer is not None:
@@ -706,16 +718,67 @@ class AutoThumbnailMixin:
             gate = self._preview_gate_obj = _PreviewGate(ON_DEMAND_LIMIT, self.logger)
         return gate
 
-    def _preview_pool(self):
-        with AutoThumbnailMixin._auto_thumbnailer_lock:
-            if self._preview_pool_obj is None:
-                self._preview_pool_obj = ThreadPoolExecutor(
-                    ON_DEMAND_LIMIT, thread_name_prefix=POOL_PREFIX
-                )
-            return self._preview_pool_obj
+    def _image_pool(self):
+        """The interactive image pool (#523): IMAGE_POOL_SIZE threads for view
+        previews (behind their gate), card facts and inspector reads, so
+        image buffers never spread over the default executor's threads.
 
-    def _preview_pool_threads(self):
-        pool = self._preview_pool_obj
+        None after the package teardown (``close_auto_thumbnails(final=True)``):
+        a late request then runs on the default executor (``run_in_executor``
+        with None) and starts no thread the teardown no longer stops.
+        """
+        with AutoThumbnailMixin._auto_thumbnailer_lock:
+            if self._image_pool_obj is None and not self._auto_thumbnails_shut:
+                self._image_pool_obj = ThreadPoolExecutor(
+                    IMAGE_POOL_SIZE, thread_name_prefix=POOL_PREFIX
+                )
+            return self._image_pool_obj
+
+    async def _run_image(self, func, *args, **kwargs):
+        """``_run_in_executor`` for interactive image work: the image pool.
+
+        After the teardown, or with the pool shut down in between (a test
+        reset), the call runs on the default executor as before.
+        """
+        call = functools.partial(func, *args, **kwargs)
+        loop = asyncio.get_running_loop()
+        try:
+            future = loop.run_in_executor(self._image_pool(), call)
+        except RuntimeError:  # submit refused: the pool was shut down
+            future = loop.run_in_executor(None, call)
+        return await future
+
+    def _map_image(self, func, items):
+        """``func`` over *items* on the image pool, in order (blocking).
+
+        Called from an image pool thread, after the teardown, or with the
+        pool shut down in between (its queued items are cancelled), the
+        items it did not run run on the calling thread.
+        """
+        items = list(items)
+        pool = None if not items or _on_image_thread() else self._image_pool()
+        if pool is None:
+            return [func(item) for item in items]
+        futures = []
+        try:
+            for item in items:
+                futures.append(pool.submit(func, item))
+        except RuntimeError:
+            pass  # shut down in between: the rest run here
+        results = []
+        for index, item in enumerate(items):
+            future = futures[index] if index < len(futures) else None
+            if future is None or future.cancelled():
+                results.append(func(item))
+                continue
+            try:
+                results.append(future.result())
+            except CancelledError:  # cancelled while this caller waited
+                results.append(func(item))
+        return results
+
+    def _image_pool_threads(self):
+        pool = self._image_pool_obj
         return [] if pool is None else list(getattr(pool, "_threads", ()))
 
     def _video_placeholder_bytes(self):
@@ -730,7 +793,7 @@ class AutoThumbnailMixin:
         return await self._preview_gate().run(
             flight_key(Path(dst).parent, (Path(dst).name,)),
             functools.partial(self._ensure_view, src, dst, is_video),
-            self._preview_pool(),
+            self._image_pool(),
         )
 
     def _ensure_view(self, src, dst, is_video):
@@ -774,13 +837,13 @@ class AutoThumbnailMixin:
         The flight answers only the outcome (a history flight may be the one
         joined); the file it previews is derived here: the preview path is
         the request's own, and a fallback looks its source up again on the
-        view pool (bounded by it, never the default executor).
+        image pool (bounded by it, never the default executor).
         """
         if _has_traversal(filepath) or not _is_preview_request(filepath):
             return None
         parts = tuple(filepath.split("/"))
         gate = self._preview_gate()
-        pool = self._preview_pool()
+        pool = self._image_pool()
         for root in output_dirs:
             root = Path(root)
             outcome = await gate.run(

py/api/thumbnail_convert.py

@@ -153,6 +153,7 @@ class ThumbnailConvertMixin:
             job.log_line("Conversion failed · internal error")
             state = "failed"
         job.finish(state)
+        await self._release_job_memory()
 
     async def _convert_job_body(self, job, options):
         output_dirs = await self._run_in_executor(self._get_all_output_dirs)

py/api/thumbnail_jobs.py

@@ -226,6 +226,7 @@ class ThumbnailJobsMixin:
             )
             state = "failed"
         job.finish(state)
+        await self._release_job_memory()
 
     async def _thumbnail_job_body(self, job, options):
         """Plan, then generate in worker batches; returns the final state.