wip: purgeable arenas; fix asan warnings

src/arena.c

@@ -133,7 +133,7 @@ static bool mi_arena_alloc(mi_arena_t* arena, size_t blocks, mi_bitmap_index_t*
 {
   size_t idx = 0; // mi_atomic_load_relaxed(&arena->search_idx);  // start from last search; ok to be relaxed as the exact start does not matter
   if (_mi_bitmap_try_find_from_claim_across(arena->blocks_inuse, arena->field_count, idx, blocks, bitmap_idx)) {
-    mi_atomic_store_relaxed(&arena->search_idx, mi_bitmap_index_field(*bitmap_idx));  // start search from found location next time around
+    mi_atomic_store_relaxed(&arena->search_idx, mi_bitmap_index_field(*bitmap_idx));  // start search from found location next time around    
     return true;
   };
   return false;
@@ -189,6 +189,8 @@ static mi_decl_noinline void* mi_arena_alloc_from(mi_arena_t* arena, size_t aren
     // no need to commit, but check if already fully committed
     *commit = _mi_bitmap_is_claimed_across(arena->blocks_committed, arena->field_count, needed_bcount, bitmap_index);
   }
+  
+  mi_track_mem_undefined(p,needed_bcount*MI_ARENA_BLOCK_SIZE);
   return p;
 }
 
@@ -300,7 +302,7 @@ void* _mi_arena_alloc_aligned(size_t size, size_t alignment, size_t align_offset
          p = mi_arena_alloc_in(arena_id, numa_node, size, alignment, commit, large, is_pinned, is_zero, req_arena_id, memid, tld);        
          if (p != NULL) return p;
       }
-    }
+    }    
   }
 
   // finally, fall back to the OS
@@ -356,10 +358,11 @@ static void mi_arena_purge(mi_arena_t* arena, size_t bitmap_idx, size_t blocks,
   const size_t size = blocks * MI_ARENA_BLOCK_SIZE;
   void* const p = arena->start + (mi_bitmap_index_bit(bitmap_idx) * MI_ARENA_BLOCK_SIZE);
   const bool decommitted = mi_os_purge(p, size, stats);
+  // clear the purged blocks
+  _mi_bitmap_unclaim_across(arena->blocks_purge, arena->field_count, blocks, bitmap_idx);
   // update committed bitmap
   if (decommitted) {
     _mi_bitmap_unclaim_across(arena->blocks_committed, arena->field_count, blocks, bitmap_idx);
-    _mi_bitmap_unclaim_across(arena->blocks_purge, arena->field_count, blocks, bitmap_idx);
   }
 }
 
@@ -520,14 +523,19 @@ void _mi_arena_free(void* p, size_t size, size_t alignment, size_t align_offset,
       _mi_error_message(EINVAL, "trying to free from non-existent arena block: %p, size %zu, memid: 0x%zx\n", p, size, memid);
       return;
     }
-    
+
     // potentially decommit
     if (!arena->allow_decommit || arena->blocks_committed == NULL) {
-      mi_assert_internal(all_committed); // note: may be not true as we may "pretend" to be not committed (in segment.c)
+      mi_assert_internal(all_committed);
     }
     else {
       mi_assert_internal(arena->blocks_committed != NULL);
       mi_assert_internal(arena->blocks_purge != NULL);
+      if (!all_committed) {
+        // assume the entire range as no longer committed
+        _mi_bitmap_unclaim_across(arena->blocks_committed, arena->field_count, blocks, bitmap_idx);
+      }
+      // (delay) purge the entire range
       mi_arena_schedule_purge(arena, bitmap_idx, blocks, stats);      
     }
     

src/os.c

@@ -411,6 +411,9 @@ static bool mi_os_resetx(void* addr, size_t size, bool reset, mi_stats_t* stats)
   if (err != 0) {
     _mi_warning_message("cannot reset OS memory (error: %d (0x%x), address: %p, size: 0x%zx bytes)\n", err, err, start, csize);
   }
+  else {
+    mi_track_mem_undefined(start, csize);
+  }
   return (err == 0);
 }
 

src/prim/unix/prim.c

@@ -380,7 +380,8 @@ int _mi_prim_commit(void* start, size_t size, bool commit) {
 }
 
 int _mi_prim_reset(void* start, size_t size) {
-  #if defined(MADV_FREE)
+  // note: disable the use of MADV_FREE since it leads to confusing stats :-(
+  #if 0 // defined(MADV_FREE)
   static _Atomic(size_t) advice = MI_ATOMIC_VAR_INIT(MADV_FREE);
   int oadvice = (int)mi_atomic_load_relaxed(&advice);
   int err;

src/segment.c

@@ -400,12 +400,18 @@ static void mi_segment_os_free(mi_segment_t* segment, mi_segments_tld_t* tld) {
      || !_mi_segment_cache_push(segment, size, segment->memid, &segment->commit_mask, &segment->decommit_mask, segment->mem_is_large, segment->mem_is_pinned, tld->os)) 
 #endif       
   {
-    if (!segment->mem_is_pinned) {
+    // if not all committed, an arena may decommit the whole area, but that double counts
+    // the already decommitted parts; adjust for that in the stats.
+    if (!mi_commit_mask_is_full(&segment->commit_mask)) {
       const size_t csize = _mi_commit_mask_committed_size(&segment->commit_mask, size);
-      if (csize > 0) { _mi_stat_decrease(&_mi_stats_main.committed, csize); }
+      mi_assert_internal(size > csize);
+      if (size > csize) {
+        _mi_stat_increase(&_mi_stats_main.committed, size - csize); 
+      }
     }
     _mi_abandoned_await_readers();  // wait until safe to free
-    _mi_arena_free(segment, mi_segment_size(segment), segment->mem_alignment, segment->mem_align_offset, segment->memid, segment->mem_is_pinned /* pretend not committed to not double count decommits */, tld->stats);
+    _mi_arena_free(segment, mi_segment_size(segment), segment->mem_alignment, segment->mem_align_offset, segment->memid, 
+                            mi_commit_mask_is_full(&segment->commit_mask) /* all committed? */, tld->stats);
   }
 }