add option to make fresh arena allocation associate with a local numa node

Author: daanx

include/mimalloc.h

@@ -483,6 +483,7 @@ typedef enum mi_option_e {
   mi_option_allow_thp,                  // allow transparent huge pages? (=1) (on Android =0 by default). Set to 0 to disable THP for the process.
   mi_option_minimal_purge_size,         // set minimal purge size (in KiB) (=0). By default set to either 64 or 2048 if THP is enabled.
   mi_option_arena_max_object_size,      // set maximal object size that can be allocated in an arena (in KiB) (=2GiB on 64-bit). 
+  mi_option_arena_is_numa_local,        // experimental
   _mi_option_last,
   // legacy option names
   mi_option_large_os_pages = mi_option_allow_large_os_pages,

src/arena.c

@@ -399,7 +399,7 @@ static size_t mi_arena_start_idx(mi_heap_t* heap, size_t tseq, size_t arena_cycl
   const size_t hseq   = heap->heap_seq;
   const size_t hcount = mi_atomic_load_relaxed(&heap->subproc->heap_count);
   if (arena_cycle <= 1)     return 0;
-  if (hseq==0 || hcount<=1) return (tseq % arena_cycle); // common for single heap programs
+  if (hseq==0 || hcount<=1 || arena_cycle > 0x8FF) return (tseq % arena_cycle); // common for single heap programs
 
   // spread heaps evenly among arena's, and then evenly for threads in their fraction
   size_t start;
@@ -410,8 +410,8 @@ static size_t mi_arena_start_idx(mi_heap_t* heap, size_t tseq, size_t arena_cycl
     start = (hseq % arena_cycle);
   }
   else {
-    const size_t hspot = (hseq % hcount);
-    start = (frac * hspot) / 256;
+    const size_t hspot = (hseq % hcount);  
+    start = (frac * hspot) / 256;           // (arena_cycle * (hseq % hcount)) / hcount
     if (frac >= 512) {  // at least 2 arena's per heap?
       start = start + (tseq % (frac/256));
     }
@@ -1537,7 +1537,12 @@ static mi_arena_t* mi_arena_initialize(mi_subproc_t* subproc, void* start,
   arena->is_exclusive = exclusive;
   arena->slice_count = slice_count;
   arena->info_slices = info_slices;
-  arena->numa_node = numa_node; // TODO: or get the current numa node if -1? (now it allows anyone to allocate on -1)
+  if (numa_node<0 && mi_option_is_enabled(mi_option_arena_is_numa_local)) {
+    arena->numa_node = _mi_os_numa_node();
+  }
+  else {
+    arena->numa_node = numa_node;
+  }
   arena->purge_expire = 0;
   arena->commit_fun = commit_fun;
   arena->commit_fun_arg = commit_fun_arg;

src/options.c

@@ -178,6 +178,7 @@ static mi_option_desc_t mi_options[_mi_option_last] =
   { 0,   MI_OPTION_UNINIT, MI_OPTION(minimal_purge_size) },       // set minimal purge size (in KiB) (=0). Using 0 resolves to either 64 (or 2048 if `mi_option_allow_thp==2`).
   { MI_DEFAULT_ARENA_MAX_OBJECT_SIZE,   
          MI_OPTION_UNINIT, MI_OPTION(arena_max_object_size) },    // set maximal object size that can be allocated in an arena (in KiB) (=2GiB on 64-bit). 
+  { 0,   MI_OPTION_UNINIT, MI_OPTION(arena_is_numa_local) },      // associate local numa node with an initial arena allocation
 };
 
 static void mi_option_init(mi_option_desc_t* desc);