Switch to 64bit bitmask and bug fixes

include/mimalloc.h

@@ -349,6 +349,7 @@ typedef enum mi_option_e {
   mi_option_disallow_arena_alloc,       // 1 = do not use arena's for allocation (except if using specific arena id's)
   mi_option_retry_on_oom,               // retry on out-of-memory for N milli seconds (=400), set to 0 to disable retries. (only on windows)
   mi_option_max_segments_per_heap,        // max number of segments that heap can own
+  mi_option_heap_collect_abandoned_interval, // interval (in ms) between collecting abandoned segments when a heap drops exessive segments
   _mi_option_last,
   // legacy option names
   mi_option_large_os_pages = mi_option_allow_large_os_pages,

include/mimalloc/types.h

@@ -220,12 +220,13 @@ typedef int32_t  mi_ssize_t;
 #define MI_MAX_ALLOC_SIZE   PTRDIFF_MAX
 #endif
 
-#define MI_FREE_SPACE_MASK_BIT_COUNT 31
+#define MI_FREE_SPACE_MASK_BIT_COUNT 63
 #define MI_FREE_SPACE_BINS_PER_BIT (MI_BIN_HUGE/MI_FREE_SPACE_MASK_BIT_COUNT)
-#define MI_FREE_SPACE_MASK_ALL ((size_t)0xFFFFFFFF)
-#define MI_FREE_SPACE_MASK_ABANDONED ((size_t)0x80000000)
+#define MI_FREE_SPACE_MASK_ALL ((size_t)0xFFFFFFFFFFFFFFFF)
+#define MI_FREE_SPACE_MASK_ABANDONED ((size_t)0x8000000000000000)
 #define MI_FREE_SPACE_MASK_ANY (MI_FREE_SPACE_MASK_ALL & (~MI_FREE_SPACE_MASK_ABANDONED))
 
+
 // ------------------------------------------------------
 // Mimalloc pages contain allocated blocks
 // ------------------------------------------------------
@@ -544,6 +545,7 @@ struct mi_heap_s {
   size_t                page_retired_min;                    // smallest retired index (retired pages are fully free, but still in the page queues)
   size_t                page_retired_max;                    // largest retired index into the `pages` array.
   mi_heap_t*            next;                                // list of heaps per thread
+  mi_msecs_t            last_abandoned_collect_time;
   bool                  no_reclaim;                          // `true` if this heap should not reclaim abandoned pages
   uint8_t               tag;                                 // custom tag, can be used for separating heaps based on the object types
   mi_page_t*            pages_free_direct[MI_PAGES_DIRECT];  // optimize: array where every entry points a page with possibly free blocks in the corresponding queue for that size.

src/heap.c

@@ -230,6 +230,7 @@ void _mi_heap_init(mi_heap_t* heap, mi_tld_t* tld, mi_arena_id_t arena_id, bool
   // push on the thread local heaps list
   heap->next = heap->tld->heaps;
   heap->tld->heaps = heap;
+  heap->last_abandoned_collect_time = 0;
 }
 
 mi_decl_nodiscard mi_heap_t* mi_heap_new_in_arena(mi_arena_id_t arena_id) {
@@ -702,6 +703,7 @@ static mi_decl_noinline void mi_segment_visit_pages(mi_heap_t* heap, mi_segment_
 }
 
 void mi_heap_drop_segment(mi_heap_t* heap, size_t targetSegmentCount) {
+    bool segmentsDropped = false;
 
     while (heap->tld->segments.count >= targetSegmentCount) {
 
@@ -711,6 +713,7 @@ void mi_heap_drop_segment(mi_heap_t* heap, size_t targetSegmentCount) {
             break;
         }
 
+        segmentsDropped = true;
         // 2. when abandoning, mark all pages to no longer add to delayed_free
         mi_segment_visit_pages(heap, segmentToAbandon, &mi_heap_page_never_delayed_free, NULL);
 
@@ -723,6 +726,18 @@ void mi_heap_drop_segment(mi_heap_t* heap, size_t targetSegmentCount) {
         mi_collect_t collect = MI_ABANDON;
         mi_segment_visit_pages(heap, segmentToAbandon, &mi_heap_page_collect, &collect);
     }
+
+    if (segmentsDropped) {
+        mi_msecs_t now_msec = _mi_clock_now();
+        long collect_interval = mi_option_get(mi_option_heap_collect_abandoned_interval);
+        if ((now_msec - heap->last_abandoned_collect_time) >= collect_interval) {
+            heap->last_abandoned_collect_time = now_msec;
+
+            // collect abandoned segments (in particular, purge expired parts of segments in the abandoned segment list)
+            // note: forced purge can be quite expensive if many threads are created/destroyed so we do not force on abandonment
+            _mi_abandoned_collect(heap, false /* force? */, &heap->tld->segments);
+        }
+    }
 }
 
 void mi_heap_drop_segment_if_required(mi_heap_t* heap, size_t alloc_block_size)

src/init.c

@@ -123,6 +123,7 @@ mi_decl_cache_align const mi_heap_t _mi_heap_empty = {
   0,                // page count
   MI_BIN_FULL, 0,   // page retired min/max
   NULL,             // next
+  0,                // last_abandoned_collect_time
   false,            // can reclaim
   0,                // tag
   MI_SMALL_PAGES_EMPTY,
@@ -169,6 +170,7 @@ mi_heap_t _mi_heap_main = {
   0,                // page count
   MI_BIN_FULL, 0,   // page retired min/max
   NULL,             // next heap
+  0,                // last_abandoned_collect_time
   false,            // can reclaim
   0,                // tag
   MI_SMALL_PAGES_EMPTY,

src/options.c

@@ -94,6 +94,7 @@ static mi_option_desc_t options[_mi_option_last] =
   { 0,   UNINIT, MI_OPTION(disallow_arena_alloc) },     // 1 = do not use arena's for allocation (except if using specific arena id's)
   { 400, UNINIT, MI_OPTION(retry_on_oom) },             // windows only: retry on out-of-memory for N milli seconds (=400), set to 0 to disable retries.
   { 8,  UNINIT, MI_OPTION(max_segments_per_heap) },       // max number of segments that heap can own.
+  { 2000,  UNINIT, MI_OPTION(heap_collect_abandoned_interval) },       // max number of segments that heap can own.
 };
 
 static void mi_option_init(mi_option_desc_t* desc);

src/segment.c

@@ -1101,7 +1101,7 @@ size_t mi_free_space_mask_from_slicecount(uint32_t slice_count)
         max_size = slice_count * MI_SEGMENT_SLICE_SIZE;
     }
     
-    free_space_mask = mi_free_space_mask_from_blocksize(max_size - 1);
+    free_space_mask = mi_free_space_mask_from_blocksize(max_size);
     free_space_mask = free_space_mask | (free_space_mask - 1); // mark all allocations with size < max_size as available
 
     return free_space_mask;
@@ -1187,6 +1187,7 @@ static bool mi_segment_check_free(mi_segment_t* segment, size_t slices_needed, s
 {
   mi_assert_internal(mi_segment_is_abandoned(segment));
   bool has_page = false;
+  size_t free_space_mask = 0;
 
   // for all slices
   const mi_slice_t* end;
@@ -1208,6 +1209,7 @@ static bool mi_segment_check_free(mi_segment_t* segment, size_t slices_needed, s
         if (slice->slice_count >= slices_needed) {
           has_page = true;
         }
+        free_space_mask |= mi_free_space_mask_from_slicecount(slice->slice_count);
       }
       else if (mi_page_block_size(page) == block_size && mi_page_has_any_available(page)) {
         // a page has available free blocks of the right size
@@ -1222,6 +1224,10 @@ static bool mi_segment_check_free(mi_segment_t* segment, size_t slices_needed, s
     }
     slice = slice + slice->slice_count;
   }
+
+  if (free_space_mask != 0) {
+      mi_atomic_or_acq_rel(&segment->free_space_mask, free_space_mask);
+  }
   return has_page;
 }