Add mi_heap_page_utilization

include/mimalloc.h

@@ -285,6 +285,9 @@ mi_decl_export bool mi_manage_os_memory(void* start, size_t size, bool is_commit
 
 mi_decl_export void mi_debug_show_arenas(void) mi_attr_noexcept;
 
+mi_decl_export bool mi_heap_page_is_underutilized(mi_heap_t* heap, void* p, float ratio) mi_attr_noexcept;
+mi_decl_export float mi_heap_page_utilization(mi_heap_t* heap, void* p) mi_attr_noexcept;
+
 // Experimental: heaps associated with specific memory arena's
 typedef int mi_arena_id_t;
 mi_decl_export void* mi_arena_area(mi_arena_id_t arena_id, size_t* size);

include/mimalloc/types.h

@@ -85,7 +85,7 @@ terms of the MIT license. A copy of the license can be found in the file
 // Encoded free lists allow detection of corrupted free lists
 // and can detect buffer overflows, modify after free, and double `free`s.
 #if (MI_SECURE>=3 || MI_DEBUG>=1)
-#define MI_ENCODE_FREELIST  1
+//#define MI_ENCODE_FREELIST  1
 #endif
 
 

src/alloc.c

@@ -1044,6 +1044,44 @@ mi_decl_nodiscard void* mi_new_reallocn(void* p, size_t newcount, size_t size) {
   }
 }
 
+float mi_heap_page_utilization(mi_heap_t* heap, void* p) mi_attr_noexcept {
+  mi_page_t* page = _mi_ptr_page(p);   // get the page that this belongs to
+
+  mi_heap_t* page_heap = (mi_heap_t*)(mi_atomic_load_acquire(&(page)->xheap));
+
+  // the heap id matches and it is not a full page
+  if (mi_likely(page_heap == heap && page->flags.x.in_full == 0)) {
+    // first in the list, meaning it's the head of page queue, thus being used for malloc
+    if (page->prev == NULL)
+      return 1.0;
+
+    // this page belong to this heap and is not first in the page queue. Lets check its
+    // utilization.
+    float ratio = (float)page->used / (float)page->capacity;
+    mi_assert_internal(ratio <= 1.0);
+    return ratio;
+  }
+  return 1.0;
+}
+
+bool mi_heap_page_is_underutilized(mi_heap_t* heap, void* p, float ratio) mi_attr_noexcept {
+  mi_page_t* page = _mi_ptr_page(p);   // get the page that this belongs to
+
+  mi_heap_t* page_heap = (mi_heap_t*)(mi_atomic_load_acquire(&(page)->xheap));
+
+  // the heap id matches and it is not a full page
+  if (mi_likely(page_heap == heap && page->flags.x.in_full == 0)) {
+    // first in the list, meaning it's the head of page queue, thus being used for malloc
+    if (page->prev == NULL)
+      return false;
+
+    // this page belong to this heap and is not first in the page queue. Lets check its
+    // utilization.
+    return page->used <= (unsigned)(page->capacity * ratio);
+  }
+  return false;
+}
+
 // ------------------------------------------------------
 // ensure explicit external inline definitions are emitted!
 // ------------------------------------------------------