make reclaim tries a percentage of the abandoned count

include/mimalloc/internal.h

@@ -126,6 +126,7 @@ void       _mi_arena_unsafe_destroy_all(mi_stats_t* stats);
 
 bool       _mi_arena_segment_clear_abandoned(mi_memid_t memid);
 void       _mi_arena_segment_mark_abandoned(mi_memid_t memid);
+size_t     _mi_arena_segment_abandoned_count(void);
 
 typedef struct mi_arena_field_cursor_s { // abstract
   mi_arena_id_t  start;   

src/arena.c

@@ -733,14 +733,18 @@ bool _mi_arena_contains(const void* p) {
   This is used to atomically abandon/reclaim segments 
   (and crosses the arena API but it is convenient to have here).
   Abandoned segments still have live blocks; they get reclaimed
-  when a thread frees in it, or when a thread needs a fresh
+  when a thread frees a block in it, or when a thread needs a fresh
   segment; these threads scan the abandoned segments through
   the arena bitmaps.
 ----------------------------------------------------------- */
 
-// Maintain these for debug purposes
+// Maintain a count of all abandoned segments
 static mi_decl_cache_align _Atomic(size_t)abandoned_count;
 
+size_t _mi_arena_segment_abandoned_count(void) {
+  return mi_atomic_load_relaxed(&abandoned_count);
+}
+
 // reclaim a specific abandoned segment; `true` on success.
 bool _mi_arena_segment_clear_abandoned(mi_memid_t memid ) 
 {
@@ -885,7 +889,7 @@ static bool mi_manage_os_memory_ex2(void* start, size_t size, bool is_large, int
   // consequetive bitmaps
   arena->blocks_dirty     = &arena->blocks_inuse[fields];     // just after inuse bitmap
   arena->blocks_abandoned = &arena->blocks_inuse[2 * fields]; // just after dirty bitmap
-  arena->blocks_committed = (arena->memid.is_pinned ? NULL : &arena->blocks_inuse[3*fields]); // just after abandonde bitmap
+  arena->blocks_committed = (arena->memid.is_pinned ? NULL : &arena->blocks_inuse[3*fields]); // just after abandoned bitmap
   arena->blocks_purge     = (arena->memid.is_pinned ? NULL : &arena->blocks_inuse[4*fields]); // just after committed bitmap
   // initialize committed bitmap?
   if (arena->blocks_committed != NULL && arena->memid.initially_committed) {

src/options.c

@@ -81,7 +81,7 @@ static mi_option_desc_t options[_mi_option_last] =
   { 100, UNINIT, MI_OPTION(os_tag) },                   // only apple specific for now but might serve more or less related purpose
   { 16,  UNINIT, MI_OPTION(max_errors) },               // maximum errors that are output
   { 16,  UNINIT, MI_OPTION(max_warnings) },             // maximum warnings that are output
-  { 16,  UNINIT, MI_OPTION(max_segment_reclaim)},       // max. number of segment reclaims from the abandoned segments per try.
+  { 10,  UNINIT, MI_OPTION(max_segment_reclaim)},       // max. percentage of the abandoned segments per try.
   { 0,   UNINIT, MI_OPTION(destroy_on_exit)},           // release all OS memory on process exit; careful with dangling pointer or after-exit frees!
   #if (MI_INTPTR_SIZE>4)
   { 1024L * 1024L, UNINIT, MI_OPTION(arena_reserve) },  // reserve memory N KiB at a time

src/segment.c

@@ -921,7 +921,13 @@ static mi_segment_t* mi_segment_try_reclaim(mi_heap_t* heap, size_t block_size,
   *reclaimed = false;  
   mi_segment_t* segment;
   mi_arena_field_cursor_t current; _mi_arena_field_cursor_init(heap,&current);
-  long max_tries = mi_option_get_clamp(mi_option_max_segment_reclaim, 0, 1024);     // limit the work to bound allocation times
+  
+  // limit the tries to 10% (default) of the abandoned segments with at least 8 tries, and at most 1024.
+  const size_t perc = (size_t)mi_option_get_clamp(mi_option_max_segment_reclaim, 0, 100);
+  if (perc <= 0) return NULL;
+  const size_t abandoned_count = _mi_arena_segment_abandoned_count();
+  const size_t relative_count = (abandoned_count > 10000 ? (abandoned_count / 100) * perc : (abandoned_count * perc) / 100); // avoid overflow
+  long max_tries = (long)(relative_count < 8 ? 8 : (relative_count > 1024 ? 1024 : relative_count));
   while ((max_tries-- > 0) && ((segment = _mi_arena_segment_clear_abandoned_next(&current)) != NULL)) 
   {
     segment->abandoned_visits++;