wip: purgeable arenas, various fixes

include/mimalloc/types.h

@@ -350,7 +350,7 @@ typedef enum mi_segment_kind_e {
 // is still tracked in fine-grained MI_COMMIT_SIZE chunks)
 // ------------------------------------------------------
 
-#define MI_MINIMAL_COMMIT_SIZE      (1*MI_SEGMENT_SLICE_SIZE)            // most fine-grained
+#define MI_MINIMAL_COMMIT_SIZE      (1*MI_SEGMENT_SLICE_SIZE)            
 #define MI_COMMIT_SIZE              (MI_SEGMENT_SLICE_SIZE)              // 64KiB
 #define MI_COMMIT_MASK_BITS         (MI_SEGMENT_SIZE / MI_COMMIT_SIZE)  
 #define MI_COMMIT_MASK_FIELD_BITS    MI_SIZE_BITS

src/arena.c

@@ -182,7 +182,7 @@ static mi_decl_noinline void* mi_arena_alloc_from(mi_arena_t* arena, size_t aren
     if (any_uncommitted) {
       bool commit_zero;
       _mi_os_commit(p, needed_bcount * MI_ARENA_BLOCK_SIZE, &commit_zero, tld->stats);
-      if (commit_zero) *is_zero = true;
+      if (commit_zero) { *is_zero = true; }
     }
   }
   else {
@@ -190,7 +190,7 @@ static mi_decl_noinline void* mi_arena_alloc_from(mi_arena_t* arena, size_t aren
     *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);
+  // mi_track_mem_undefined(p,needed_bcount*MI_ARENA_BLOCK_SIZE);
   return p;
 }
 
@@ -297,7 +297,11 @@ void* _mi_arena_alloc_aligned(size_t size, size_t alignment, size_t align_offset
         mi_atomic_load_relaxed(&mi_arena_count) < 3*(MI_MAX_ARENAS/4) )  // not too many arenas already?        
     {      
       mi_arena_id_t arena_id = 0;
-      const bool arena_commit = _mi_os_has_overcommit() || mi_option_is_enabled(mi_option_eager_arena_commit);
+
+      bool arena_commit = _mi_os_has_overcommit();
+      if (mi_option_get(mi_option_eager_arena_commit) == 1) { arena_commit = true; } 
+      else if (mi_option_get(mi_option_eager_arena_commit) == 0) { arena_commit = false; } 
+
       if (mi_reserve_os_memory_ex(arena_reserve, arena_commit /* commit */, *large /* allow large*/, false /* exclusive */, &arena_id) == 0) {
          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;
@@ -513,6 +517,9 @@ void _mi_arena_free(void* p, size_t size, size_t alignment, size_t align_offset,
       return;
     }
 
+    // need to set all memory to undefined as some parts may still be marked as no_access (like padding etc.)
+    mi_track_mem_undefined(p,size);
+
     // potentially decommit
     if (!arena->allow_decommit || arena->blocks_committed == NULL) {
       mi_assert_internal(all_committed);
@@ -523,6 +530,7 @@ void _mi_arena_free(void* p, size_t size, size_t alignment, size_t align_offset,
       if (!all_committed) {
         // assume the entire range as no longer committed
         _mi_bitmap_unclaim_across(arena->blocks_committed, arena->field_count, blocks, bitmap_idx);
+        mi_track_mem_noaccess(p,size);
       }
       // (delay) purge the entire range
       mi_arena_schedule_purge(arena, bitmap_idx, blocks, stats);      

src/options.c

@@ -60,7 +60,7 @@ static mi_option_desc_t options[_mi_option_last] =
 
   // Some of the following options are experimental and not all combinations are valid. Use with care.
   { 1, UNINIT, MI_OPTION(eager_commit) },        // commit per segment directly (8MiB)  (but see also `eager_commit_delay`)
-  { 0, UNINIT, MI_OPTION_LEGACY(eager_arena_commit,eager_region_commit) },
+  { 2, UNINIT, MI_OPTION_LEGACY(eager_arena_commit,eager_region_commit) },
   { 0, UNINIT, MI_OPTION_LEGACY(purge_decommits,reset_decommits) },
   { 0, UNINIT, MI_OPTION(large_os_pages) },      // use large OS pages, use only with eager commit to prevent fragmentation of VMA's
   { 0, UNINIT, MI_OPTION(reserve_huge_os_pages) },  // per 1GiB huge pages

src/prim/unix/prim.c

@@ -342,22 +342,6 @@ static void unix_mprotect_hint(int err) {
 
 
 int _mi_prim_commit(void* start, size_t size, bool commit) {
-  /*
-  #if 0 && defined(MAP_FIXED) && !defined(__APPLE__)
-  // Linux: disabled for now as mmap fixed seems much more expensive than MADV_DONTNEED (and splits VMA's?)
-  if (commit) {
-    // commit: just change the protection
-    err = mprotect(start, csize, (PROT_READ | PROT_WRITE));
-    if (err != 0) { err = errno; }
-  }
-  else {
-    // decommit: use mmap with MAP_FIXED to discard the existing memory (and reduce rss)
-    const int fd = mi_unix_mmap_fd();
-    void* p = mmap(start, csize, PROT_NONE, (MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE), fd, 0);
-    if (p != start) { err = errno; }
-  }
-  #else
-  */
   int err = 0;
   if (commit) {
     // commit: ensure we can access the area

src/segment.c

@@ -756,7 +756,7 @@ static void mi_segment_slice_split(mi_segment_t* segment, mi_slice_t* slice, siz
   mi_assert_internal(segment->kind != MI_SEGMENT_HUGE);
   size_t next_index = mi_slice_index(slice) + slice_count;
   size_t next_count = slice->slice_count - slice_count;
-  mi_segment_span_free(segment, next_index, next_count, false /* don't decommit left-over part */, tld);
+  mi_segment_span_free(segment, next_index, next_count, false /* don't purge left-over part */, tld);
   slice->slice_count = (uint32_t)slice_count;
 }
 
@@ -969,7 +969,7 @@ static mi_segment_t* mi_segment_alloc(size_t required, size_t page_alignment, mi
   // initialize initial free pages
   if (segment->kind == MI_SEGMENT_NORMAL) { // not a huge page
     mi_assert_internal(huge_page==NULL);
-    mi_segment_span_free(segment, info_slices, segment->slice_entries - info_slices, false /* don't decommit */, tld);
+    mi_segment_span_free(segment, info_slices, segment->slice_entries - info_slices, false /* don't purge */, tld);
   }
   else {
     mi_assert_internal(huge_page!=NULL);
@@ -1585,7 +1585,7 @@ static mi_page_t* mi_segment_huge_page_alloc(size_t size, size_t page_alignment,
     mi_assert_internal(psize - (aligned_p - start) >= size);      
     uint8_t* decommit_start = start + sizeof(mi_block_t);              // for the free list
     ptrdiff_t decommit_size = aligned_p - decommit_start;
-    _mi_os_decommit(decommit_start, decommit_size, &_mi_stats_main);   // note: cannot use segment_decommit on huge segments    
+    _mi_os_reset(decommit_start, decommit_size, &_mi_stats_main);   // note: cannot use segment_decommit on huge segments    
   }
   
   return page;
@@ -1630,7 +1630,7 @@ void _mi_segment_huge_page_reset(mi_segment_t* segment, mi_page_t* page, mi_bloc
   if (segment->allow_decommit) {
     const size_t csize = mi_usable_size(block) - sizeof(mi_block_t);
     uint8_t* p = (uint8_t*)block + sizeof(mi_block_t);
-    _mi_os_decommit(p, csize, &_mi_stats_main);  // note: cannot use segment_decommit on huge segments
+    _mi_os_reset(p, csize, &_mi_stats_main);  // note: cannot use segment_decommit on huge segments
   }
 }
 #endif