add max segment reclaim as an option

include/mimalloc.h

@@ -321,6 +321,7 @@ typedef enum mi_option_e {
   mi_option_reset_delay,
   mi_option_use_numa_nodes,           // 0 = use available numa nodes, otherwise use at most N nodes.
   mi_option_limit_os_alloc,           // 1 = do not use OS memory for allocation (but only reserved arenas)
+  mi_option_max_segment_reclaim,      
   mi_option_os_tag,
   mi_option_max_errors,
   mi_option_max_warnings,
@@ -335,6 +336,7 @@ mi_decl_export void mi_option_set_enabled(mi_option_t option, bool enable);
 mi_decl_export void mi_option_set_enabled_default(mi_option_t option, bool enable);
 
 mi_decl_nodiscard mi_decl_export long mi_option_get(mi_option_t option);
+mi_decl_nodiscard mi_decl_export long mi_option_get_clamp(mi_option_t option, long min, long max);
 mi_decl_export void mi_option_set(mi_option_t option, long value);
 mi_decl_export void mi_option_set_default(mi_option_t option, long value);
 

src/init.c

@@ -562,7 +562,7 @@ void mi_process_init(void) mi_attr_noexcept {
   mi_stats_reset();  // only call stat reset *after* thread init (or the heap tld == NULL)
 
   if (mi_option_is_enabled(mi_option_reserve_huge_os_pages)) {
-    size_t pages = mi_option_get(mi_option_reserve_huge_os_pages);
+    size_t pages = mi_option_get_clamp(mi_option_reserve_huge_os_pages, 0, 128*1024);
     long reserve_at = mi_option_get(mi_option_reserve_huge_os_pages_at);
     if (reserve_at != -1) {
       mi_reserve_huge_os_pages_at(pages, reserve_at, pages*500);

src/options.c

@@ -90,6 +90,7 @@ static mi_option_desc_t options[_mi_option_last] =
   { 100, UNINIT, MI_OPTION(reset_delay) },       // reset delay in milli-seconds
   { 0,   UNINIT, MI_OPTION(use_numa_nodes) },    // 0 = use available numa nodes, otherwise use at most N nodes.
   { 0,   UNINIT, MI_OPTION(limit_os_alloc) },    // 1 = do not use OS memory for allocation (but only reserved arenas)
+  { 8,   UNINIT, MI_OPTION(max_segment_reclaim)},// max. number of segment reclaims from the abandoned segments per try.
   { 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
@@ -125,6 +126,11 @@ mi_decl_nodiscard long mi_option_get(mi_option_t option) {
   return desc->value;
 }
 
+mi_decl_nodiscard long mi_option_get_clamp(mi_option_t option, long min, long max) {
+  long x = mi_option_get(option);
+  return (x < min ? min : (x > max ? max : x));
+}
+
 void mi_option_set(mi_option_t option, long value) {
   mi_assert(option >= 0 && option < _mi_option_last);
   if (option < 0 || option >= _mi_option_last) return;

src/region.c

@@ -122,7 +122,7 @@ static size_t mi_good_commit_size(size_t size) {
 */
 
 // Return if a pointer points into a region reserved by us.
-bool mi_is_in_heap_region(const void* p) mi_attr_noexcept {
+mi_decl_nodiscard bool mi_is_in_heap_region(const void* p) mi_attr_noexcept {
   if (p==NULL) return false;
   size_t count = mi_atomic_load_relaxed(&regions_count);
   for (size_t i = 0; i < count; i++) {

src/segment.c

@@ -1112,7 +1112,7 @@ static mi_segment_t* mi_segment_try_reclaim(mi_heap_t* heap, size_t block_size,
 {
   *reclaimed = false;
   mi_segment_t* segment;
-  int max_tries = 8;     // limit the work to bound allocation times
+  long max_tries = mi_option_get_clamp(mi_option_max_segment_reclaim, 8, 1024);     // limit the work to bound allocation times  
   while ((max_tries-- > 0) && ((segment = mi_abandoned_pop()) != NULL)) {
     segment->abandoned_visits++;
     bool all_pages_free;