Make Gen-0 size semi-independent of Gen-1 minimum size.

gc.c

@@ -387,10 +387,10 @@ static inline size_t gc_align(size_t nbytes)
   return ((nbytes + GC_ALIGNMENT - 1) & ~(GC_ALIGNMENT - 1));
 }
 
-void gc_init(size_t min_size, size_t max_size)
+void gc_init(size_t gen0_size, size_t gen1_min_size, size_t gen1_max_size)
 {
-  gc_gen0_init(min_size);
-  gc_gen1_init(min_size, max_size);
+  gc_gen0_init(gen0_size);
+  gc_gen1_init(gen1_min_size, gen1_max_size);
 
   gc_weak_box_list    = NIL;
   gc_will_list        = NIL;
@@ -426,10 +426,10 @@ static void gc_poison_region(void *start, size_t size, value_t tag)
 
 /* These private variables are exported ONLY for use by is_gen0_object(). */
 char *gc_gen0_range;
-size_t gc_gen0_size;
+char *gc_gen0_range_end;
 
+static size_t gc_gen0_size;
 static char *gc_gen0_free_ptr;
-static char *gc_gen0_range_end;
 
 /* Used to signal that Gen-0 pass has been obviated by Gen-1 collection. */
 static jmp_buf gc_gen0_end_ctx;
@@ -455,6 +455,10 @@ static void collect_gen0_garbage(void)
 {
   if (gc_enabled)
   {
+#ifndef NDEBUG
+    size_t initial_gen1_free_space;
+#endif
+
 #ifndef NO_STATS
     size_t initial_free_space;
 #ifndef NO_TIMING_STATS
@@ -469,6 +473,10 @@ static void collect_gen0_garbage(void)
     assert(!gc_in_gen0_collection);
     assert(!gc_in_gen1_collection);
 
+#ifndef NDEBUG
+    initial_gen1_free_space = gc_gen1_free_space();
+#endif
+
     /* If we trigger a Gen-1 collection at any point then we are done. */
     /* Full collection will pull in any current Gen-0 objects. */
     if (setjmp(gc_gen0_end_ctx) == 0)
@@ -548,6 +556,8 @@ static void collect_gen0_garbage(void)
       /* 4. Reset Gen-0 range to 'empty' state. */
       gc_gen0_free_ptr = gc_gen0_range;
 
+      //debug(("Finished Gen-0 collection; added %d bytes to Gen-1 heap.\n", initial_gen1_free_space - gc_gen1_free_space()));
+
 #ifndef NO_STATS
 #ifndef NO_TIMING_STATS
       {
@@ -644,7 +654,9 @@ static inline bool gc_object_left_behind(value_t v)
 
 static void gc_gen1_init(size_t min_size, size_t max_size)
 {
-  release_assert(min_size <= ((max_size+1)/2));
+  release_assert(gc_gen0_size > 0);
+  release_assert(max_size >= gc_gen0_size);
+  release_assert(min_size <= (max_size - gc_gen0_size));
 
   gc_gen1_ranges[0] = (char*)malloc(max_size);
   gc_gen1_ranges[1] = (char*)malloc(max_size);
@@ -656,7 +668,7 @@ static void gc_gen1_init(size_t min_size, size_t max_size)
 
   gc_gen1_min_size   = min_size;
   gc_gen1_max_size   = max_size;
-  gc_gen1_soft_limit = 2*min_size;
+  gc_gen1_soft_limit = min_size + gc_gen0_size;
   gc_gen1_range_end  = gc_gen1_free_ptr + gc_gen1_soft_limit;
 
   gc_gen1_max_blocks = ((size_t)2 << 30) / GC_DIRTY_BLOCK_SIZE;
@@ -670,7 +682,8 @@ static void gc_gen1_init(size_t min_size, size_t max_size)
 
 static void gc_gen1_clear_dirty_bits(void)
 {
-  memset(gc_gen1_dirty_bits, 0, sizeof(uint32_t) * ((gc_gen1_max_blocks + 31) / 32));
+  const size_t block_groups = (gc_gen1_max_blocks + 31) / 32;
+  memset(gc_gen1_dirty_bits, 0, sizeof(uint32_t) * block_groups);
 }
 
 static void *gc_alloc_gen1(size_t nbytes)
@@ -679,11 +692,12 @@ static void *gc_alloc_gen1(size_t nbytes)
 
   min_free = nbytes = gc_align(nbytes);
 
+  /* Ensure there is always enough room for a full collection. */
   if (!gc_in_gen1_collection)
     min_free += gc_gen0_size;
 
   if (gc_gen1_free_space() < min_free)
-    collect_gen1_garbage(nbytes);
+    collect_gen1_garbage(min_free);
 
   assert(nbytes <= gc_gen1_free_space());
 
@@ -1030,9 +1044,12 @@ static size_t gc_gen1_block_of(void *obj)
 
 void _gc_mark_updated_gen1_object(value_t v)
 {
-  const size_t block = gc_gen1_block_of(_get_object(v));
-  assert(is_object(v) && !is_gen0_object(v) && gc_gen1_block_starts[block]);
-  gc_gen1_dirty_bits[block / 32] |= (1UL << (block % 32));
+  assert(is_object(v));
+  {
+    const size_t block = gc_gen1_block_of(_get_object(v));
+    assert(is_object(v) && !is_gen0_object(v) && gc_gen1_block_starts[block]);
+    gc_gen1_dirty_bits[block / 32] |= (1UL << (block % 32));
+  }
 }
 
 static void _out_of_memory(void) __attribute__ ((noreturn));
@@ -1120,7 +1137,7 @@ static void collect_gen1_garbage(size_t min_free)
     gc_gen0_free_ptr = gc_gen0_range;
     collected_garbage = true;
     
-    //debug(("Finished collection with %d bytes to spare (out of %d bytes).\n", gc_gen1_free_space(), gc_gen1_soft_limit));
+    //debug(("Finished Gen-1 collection; active set is %d bytes.\n", gc_gen1_free_ptr - gc_gen1_ranges[gc_gen1_current_range]));
 
     gc_in_gen1_collection = false;
     gc_enabled = true;

gc.h

@@ -388,7 +388,7 @@ static inline builtin_fn_t *_get_builtin_fn(value_t v)
   return ((builtin_fn_object_t*)_get_object(v))->fn;
 }
 
-void gc_init(size_t min_size, size_t max_size);
+void gc_init(size_t gen0_size, size_t gen1_min_size, size_t gen1_max_size);
 void clear_gc_stats(void);
 void register_gc_root(gc_root_t *root, value_t v);
 void unregister_gc_root(gc_root_t *root);
@@ -414,18 +414,19 @@ static inline bool is_gen0_object(value_t v)
 {
   /* These private variables are exported ONLY for use by this inline function. */
   extern char *gc_gen0_range;
-  extern size_t gc_gen0_size;
+  extern char *gc_gen0_range_end;
 
   const char const *obj = (const char*)_get_object(v);
-  return is_object(v)
-      && (obj >= (char*)gc_gen0_range)
-      && ((obj - (char*)gc_gen0_range) < gc_gen0_size);
+  return (obj <  gc_gen0_range_end)
+      && (obj >= gc_gen0_range)
+      && is_object(v);
 }
 
 /* Don't call this directly; use the WRITE_BARRIER macro. */
 static inline void _gc_write_barrier(value_t v)
 {
-  if (is_object(v) && !is_gen0_object(v))
+  assert(is_object(v));
+  if (!is_gen0_object(v))
   {
     _gc_mark_updated_gen1_object(v);
   }