gh-112532: Tag mimalloc heaps and pages

Include/internal/mimalloc/mimalloc/internal.h

@@ -155,7 +155,7 @@ size_t     _mi_bin_size(uint8_t bin);           // for stats
 uint8_t    _mi_bin(size_t size);                // for stats
 
 // "heap.c"
-void       _mi_heap_init_ex(mi_heap_t* heap, mi_tld_t* tld, mi_arena_id_t arena_id);
+void       _mi_heap_init_ex(mi_heap_t* heap, mi_tld_t* tld, mi_arena_id_t arena_id, bool no_reclaim, uint8_t tag);
 void       _mi_heap_destroy_pages(mi_heap_t* heap);
 void       _mi_heap_collect_abandon(mi_heap_t* heap);
 void       _mi_heap_set_default_direct(mi_heap_t* heap);

Include/internal/mimalloc/mimalloc/types.h

@@ -311,6 +311,7 @@ typedef struct mi_page_s {
   uint32_t              slice_offset;      // distance from the actual page data slice (0 if a page)
   uint8_t               is_committed : 1;  // `true` if the page virtual memory is committed
   uint8_t               is_zero_init : 1;  // `true` if the page was initially zero initialized
+  uint8_t               tag : 4;           // tag from the owning heap
 
   // layout like this to optimize access in `mi_malloc` and `mi_free`
   uint16_t              capacity;          // number of blocks committed, must be the first field, see `segment.c:page_clear`
@@ -551,6 +552,7 @@ struct mi_heap_s {
   size_t                page_retired_max;                    // largest retired index into the `pages` array.
   mi_heap_t*            next;                                // list of heaps per thread
   bool                  no_reclaim;                          // `true` if this heap should not reclaim abandoned pages
+  uint8_t               tag;                                 // custom identifier for this heap
 };
 
 

Objects/mimalloc/heap.c

@@ -209,7 +209,7 @@ mi_heap_t* mi_heap_get_backing(void) {
   return bheap;
 }
 
-void _mi_heap_init_ex(mi_heap_t* heap, mi_tld_t* tld, mi_arena_id_t arena_id)
+void _mi_heap_init_ex(mi_heap_t* heap, mi_tld_t* tld, mi_arena_id_t arena_id, bool no_reclaim, uint8_t tag)
 {
   _mi_memcpy_aligned(heap, &_mi_heap_empty, sizeof(mi_heap_t));
   heap->tld = tld;
@@ -224,17 +224,19 @@ void _mi_heap_init_ex(mi_heap_t* heap, mi_tld_t* tld, mi_arena_id_t arena_id)
   heap->cookie = _mi_heap_random_next(heap) | 1;
   heap->keys[0] = _mi_heap_random_next(heap);
   heap->keys[1] = _mi_heap_random_next(heap);
+  heap->no_reclaim = no_reclaim;
+  heap->tag = tag;
+  // push on the thread local heaps list
+  heap->next = heap->tld->heaps;
+  heap->tld->heaps = heap;
 }
 
 mi_decl_nodiscard mi_heap_t* mi_heap_new_in_arena(mi_arena_id_t arena_id) {
   mi_heap_t* bheap = mi_heap_get_backing();
   mi_heap_t* heap = mi_heap_malloc_tp(bheap, mi_heap_t);  // todo: OS allocate in secure mode?
   if (heap == NULL) return NULL;
-  _mi_heap_init_ex(heap, bheap->tld, arena_id);
-  heap->no_reclaim = true;  // don't reclaim abandoned pages or otherwise destroy is unsafe
-  // push on the thread local heaps list
-  heap->next = heap->tld->heaps;
-  heap->tld->heaps = heap;
+  // don't reclaim abandoned pages or otherwise destroy is unsafe
+  _mi_heap_init_ex(heap, bheap->tld, arena_id, true, 0);
   return heap;
 }
 

Objects/mimalloc/init.c

@@ -14,7 +14,7 @@ terms of the MIT license. A copy of the license can be found in the file
 
 // Empty page used to initialize the small free pages array
 const mi_page_t _mi_page_empty = {
-  0, false, false, false,
+  0, false, false, false, 0,
   0,       // capacity
   0,       // reserved capacity
   { 0 },   // flags
@@ -121,7 +121,8 @@ mi_decl_cache_align const mi_heap_t _mi_heap_empty = {
   0,                // page count
   MI_BIN_FULL, 0,   // page retired min/max
   NULL,             // next
-  false
+  false,
+  0
 };
 
 #define tld_empty_stats  ((mi_stats_t*)((uint8_t*)&tld_empty + offsetof(mi_tld_t,stats)))
@@ -298,7 +299,7 @@ static bool _mi_heap_init(void) {
     if (td == NULL) return false;
 
     _mi_tld_init(&td->tld, &td->heap);
-    _mi_heap_init_ex(&td->heap, &td->tld, _mi_arena_id_none());
+    _mi_heap_init_ex(&td->heap, &td->tld, _mi_arena_id_none(), false, 0);
     _mi_heap_set_default_direct(&td->heap);
   }
   return false;
@@ -311,7 +312,6 @@ void _mi_tld_init(mi_tld_t* tld, mi_heap_t* bheap) {
     tld->segments.abandoned = &_mi_abandoned_default;
     tld->os.stats = &tld->stats;
     tld->heap_backing = bheap;
-    tld->heaps = bheap;
 }
 
 // Free the thread local default heap (called from `mi_thread_done`)

Objects/mimalloc/page.c

@@ -660,6 +660,7 @@ static void mi_page_init(mi_heap_t* heap, mi_page_t* page, size_t block_size, mi
   mi_assert_internal(block_size > 0);
   // set fields
   mi_page_set_heap(page, heap);
+  page->tag = heap->tag;
   page->xblock_size = (block_size < MI_HUGE_BLOCK_SIZE ? (uint32_t)block_size : MI_HUGE_BLOCK_SIZE); // initialize before _mi_segment_page_start
   size_t page_size;
   const void* page_start = _mi_segment_page_start(segment, page, &page_size);

Objects/mimalloc/segment.c

@@ -1299,6 +1299,18 @@ static bool mi_segment_check_free(mi_segment_t* segment, size_t slices_needed, s
   return has_page;
 }
 
+static mi_heap_t* mi_heap_by_tag(mi_heap_t* heap, uint8_t tag) {
+  if (heap->tag == tag) {
+    return heap;
+  }
+  for (mi_heap_t *curr = heap->tld->heaps; curr != NULL; curr = curr->next) {
+    if (curr->tag == tag) {
+      return curr;
+    }
+  }
+  return NULL;
+}
+
 // Reclaim an abandoned segment; returns NULL if the segment was freed
 // set `right_page_reclaimed` to `true` if it reclaimed a page of the right `block_size` that was not full.
 static mi_segment_t* mi_segment_reclaim(mi_segment_t* segment, mi_heap_t* heap, size_t requested_block_size, bool* right_page_reclaimed, mi_segments_tld_t* tld) {
@@ -1321,14 +1333,15 @@ static mi_segment_t* mi_segment_reclaim(mi_segment_t* segment, mi_heap_t* heap,
     if (mi_slice_is_used(slice)) {
       // in use: reclaim the page in our heap
       mi_page_t* page = mi_slice_to_page(slice);
+      mi_heap_t* target_heap = mi_heap_by_tag(heap, page->tag);
       mi_assert_internal(page->is_committed);
       mi_assert_internal(mi_page_thread_free_flag(page)==MI_NEVER_DELAYED_FREE);
       mi_assert_internal(mi_page_heap(page) == NULL);
       mi_assert_internal(page->next == NULL && page->prev==NULL);
       _mi_stat_decrease(&tld->stats->pages_abandoned, 1);
       segment->abandoned--;
       // set the heap again and allow delayed free again
-      mi_page_set_heap(page, heap);
+      mi_page_set_heap(page, target_heap);
       _mi_page_use_delayed_free(page, MI_USE_DELAYED_FREE, true); // override never (after heap is set)
       _mi_page_free_collect(page, false); // ensure used count is up to date
       if (mi_page_all_free(page)) {
@@ -1337,8 +1350,9 @@ static mi_segment_t* mi_segment_reclaim(mi_segment_t* segment, mi_heap_t* heap,
       }
       else {
         // otherwise reclaim it into the heap
-        _mi_page_reclaim(heap, page);
-        if (requested_block_size == page->xblock_size && mi_page_has_any_available(page)) {
+        _mi_page_reclaim(target_heap, page);
+        if (requested_block_size == page->xblock_size && mi_page_has_any_available(page) &&
+            heap == target_heap) {
           if (right_page_reclaimed != NULL) { *right_page_reclaimed = true; }
         }
       }

Python/pystate.c

@@ -2539,8 +2539,8 @@ tstate_mimalloc_bind(PyThreadState *tstate)
     tld->segments.abandoned = &tstate->interp->mimalloc.abandoned_pool;
 
     // Initialize each heap
-    for (Py_ssize_t i = 0; i < _Py_MIMALLOC_HEAP_COUNT; i++) {
-        _mi_heap_init_ex(&mts->heaps[i], tld, _mi_arena_id_none());
+    for (size_t i = 0; i < _Py_MIMALLOC_HEAP_COUNT; i++) {
+        _mi_heap_init_ex(&mts->heaps[i], tld, _mi_arena_id_none(), false, i);
     }
 
     // By default, object allocations use _Py_MIMALLOC_HEAP_OBJECT.