From e6b8823c069b99fa54eb1332c773b0a5ce325f3d Mon Sep 17 00:00:00 2001 From: Maik Schulze Date: Sat, 7 Nov 2026 08:21:14 +0100 Subject: [PATCH] gh-161420: Process mimalloc's delayed frees on every generic malloc again (gh-161533) (cherry picked from commit b8dd06f1d6ee3b172c58d688f122b29bb2582f9a) Co-authored-by: Maik Schulze --- .../2026-11-07-09-30-00.gh-issue-161420.mIdFre.rst | 2 ++ Objects/mimalloc/page.c | 9 ++++++--- 2 files changed, 8 insertions(+), 3 deletions(-) create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-11-07-09-30-00.gh-issue-161420.mIdFre.rst diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-11-07-09-30-00.gh-issue-161420.mIdFre.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-11-07-09-30-00.gh-issue-161420.mIdFre.rst new file mode 100644 index 000000000000000..296a2267f397be0 --- /dev/null +++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-11-07-09-30-00.gh-issue-161420.mIdFre.rst @@ -0,0 +1,2 @@ +Restore ``mimalloc``'s previous behavior of processing delayed frees from other +threads on every generic malloc call, reverting the change introduced in v2.2.2. diff --git a/Objects/mimalloc/page.c b/Objects/mimalloc/page.c index 4bce8ce76044cbe..2f26d04aaaa4d87 100644 --- a/Objects/mimalloc/page.c +++ b/Objects/mimalloc/page.c @@ -1071,6 +1071,12 @@ void* _mi_malloc_generic(mi_heap_t* heap, size_t size, bool zero, size_t huge_al } mi_assert_internal(mi_heap_is_initialized(heap)); + // Process delayed frees from other threads (but skip contended ones). + // CPython: gh-161420 showed that calling _mi_heap_delayed_free_partial only + // once every 100 generic malloc calls led to high memory usage. + // To avoid this, we now process delayed frees on every generic malloc call again. + _mi_heap_delayed_free_partial(heap); + // do administrative tasks every N generic mallocs if mi_unlikely(++heap->generic_count >= 100) { heap->generic_collect_count += heap->generic_count; @@ -1078,9 +1084,6 @@ void* _mi_malloc_generic(mi_heap_t* heap, size_t size, bool zero, size_t huge_al // call potential deferred free routines _mi_deferred_free(heap, false); - // free delayed frees from other threads (but skip contended ones) - _mi_heap_delayed_free_partial(heap); - // collect every once in a while (10000 by default) const long generic_collect = mi_option_get_clamp(mi_option_generic_collect, 1, 1000000L); if (heap->generic_collect_count >= generic_collect) {