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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Add a module for monitoring GC statistics","articleBody":"# Feature or enhancement\n\n### Proposal:\n\nI propose adding a new internal module to read the gathered statistics from GC.\nIt is supposed to work out-of-process, so we can read and show statistics in non-intrusive way and without any pauses of the monitored process.\n\nTo achieve this goal, we need to follow these steps:\n1. Extend `_PyDebugOffset` with a pointer and size to the GC stats from `_gc_runtime_state`.\n2. Add more data to the GC stats(see below).\n3. Add a small module that connects to the process you're monitoring and displays statistics.\n\nI have a working prototype.\n\nI have added the following extra data to GC stats:\n- ts_start - the timestamp of the GC collect start\n- ts_stop - the timestamp of the GC collect stop\n- heap_size - the number of live objects.\n- work_to_do - an internal value from incremental GC. It controls the number of objects that are processed by one increment.\n- object_visits - the number of objects that were visited during GC work.\n- objects_transitively_reachable - the number of objects that were reachable from the global and local roots when incremental GC is called.\n- objects_not_transitively_reachable - the number of objects that were reachable while increment was constructed.\n\nWith this module we can build tools, that gathers stats in the \"real-time\" and output it to various formats. For example, we can format data to use in [Perfetto UI](https://ui.perfetto.dev/) (image from dpo post):\n\n\u003cimg width=\"2014\" height=\"735\" alt=\"Image\" src=\"https://github.com/user-attachments/assets/2c8265cb-e5b8-48dd-88cb-9dff140db6eb\" /\u003e\n\nI want to create two PRs, one for `_PyDebugOffset` and GC stats changes, and one for new module. \n\nI want to start from GIL-enabled build. \n\ncc @pablogsal @markshannon @nascheme @colesbury \n\nAlso link to the issue https://github.com/python/cpython/issues/131253\n\n\n### Has this already been discussed elsewhere?\n\nNo response given\n\n### Links to previous discussion of this feature:\n\nhttps://discuss.python.org/t/add-a-module-for-monitoring-gc-statistics/106695\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-146532\n* gh-148057\n* gh-148071\n* gh-149284\n* gh-150969\n* gh-150970\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/sergey-miryanov","@type":"Person","name":"sergey-miryanov"},"datePublished":"2026-03-27T16:25:22.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":8},"url":"https://github.com/146527/cpython/issues/146527"}