gh-112532: Tag mimalloc heaps and pages (#113742)

* gh-112532: Tag mimalloc heaps and pages

Mimalloc pages are data structures that contain contiguous allocations
of the same block size. Note that they are distinct from operating
system pages. Mimalloc pages are contained in segments.

When a thread exits, it abandons any segments and contained pages that
have live allocations. These segments and pages may be later reclaimed
by another thread. To support GC and certain thread-safety guarantees in
free-threaded builds, we want pages to only be reclaimed by the
corresponding heap in the claimant thread. For example, we want pages
containing GC objects to only be claimed by GC heaps.

This allows heaps and pages to be tagged with an integer tag that is
used to ensure that abandoned pages are only claimed by heaps with the
same tag. Heaps can be initialized with a tag (0-15); any page allocated
by that heap copies the corresponding tag.

* Fix conversion warning

diff --git a/Include/internal/mimalloc/mimalloc/internal.h b/Include/internal/mimalloc/mimalloc/internal.h
index afd7d18a13ed8fffe97d67e02932cea03cc1dca0..887bf26c956982993e166e4abfa69147c39296e2 100644 (file)
--- a/Include/internal/mimalloc/mimalloc/internal.h
+++ b/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);

diff --git a/Include/internal/mimalloc/mimalloc/types.h b/Include/internal/mimalloc/mimalloc/types.h
index ab41b1ce990827f009f663a7a075bb7cbd066c70..b8cae24507fc5e096c779b1db90c6958639223c3 100644 (file)
--- a/Include/internal/mimalloc/mimalloc/types.h
+++ b/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
 };
 
 

diff --git a/Objects/mimalloc/heap.c b/Objects/mimalloc/heap.c
index c50e3b05590b6f13ede76500bcf6eeb8acff57c3..6468999a7d576604d439b6b24b8c95bd7324dc87 100644 (file)
--- a/Objects/mimalloc/heap.c
+++ b/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;
 }
 

diff --git a/Objects/mimalloc/init.c b/Objects/mimalloc/init.c
index 0446021fdc514e9478f616a5555ba88e65a0ea8e..5897f0512f8ef9dc6af040e8b2bd39f17463918d 100644 (file)
--- a/Objects/mimalloc/init.c
+++ b/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`)

diff --git a/Objects/mimalloc/page.c b/Objects/mimalloc/page.c
index 4610cf27afff75f24ba185e455e9ecf499e29a5c..8f0ce920156e04f0f87ca7bf41d040733e6f3acc 100644 (file)
--- a/Objects/mimalloc/page.c
+++ b/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);

diff --git a/Objects/mimalloc/segment.c b/Objects/mimalloc/segment.c
index 1040da0d9af3e94b9009976450b82e304f94302f..d9b39b03fd6c5fb4b5e9ba412e1b58269eada639 100644 (file)
--- a/Objects/mimalloc/segment.c
+++ b/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) {
@@ -1321,6 +1333,7 @@ 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);
@@ -1328,7 +1341,7 @@ static mi_segment_t* mi_segment_reclaim(mi_segment_t* segment, mi_heap_t* heap,
       _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; }
         }
       }

diff --git a/Python/pystate.c b/Python/pystate.c
index 5f515cf475dab5807e017228a26c062bbbfc8c9d..21f16b7bcdff0d080b0426f0ece8f20606440193 100644 (file)
--- a/Python/pystate.c
+++ b/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 (uint8_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.