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Lazily create objspace->id_to_obj_tbl

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This inverse table is only useful if `ObjectSpace._id2ref` is used,
which is extremely rare. The only notable exception is the `drb` gem
and even then it has an option not to rely on `_id2ref`.

So if we assume this table will never be looked up, we can just
not maintain it, and if it turns out `_id2ref` is called, we
can lock the VM and re-build it.

```
compare-ruby: ruby 3.5.0dev (2025-04-10T09:44:40Z master 684cfa42d7) +YJIT +PRISM [arm64-darwin24]
built-ruby: ruby 3.5.0dev (2025-04-10T10:13:43Z lazy-id-to-obj d3aa9626cc) +YJIT +PRISM [arm64-darwin24]
warming up..

|           |compare-ruby|built-ruby|
|:----------|-----------:|---------:|
|baseline   |     26.364M|   25.974M|
|           |       1.01x|         -|
|object_id  |     10.293M|   14.202M|
|           |           -|     1.38x|
```
This commit is contained in:
Jean Boussier 2025-04-10 11:53:39 +02:00
parent b68172caad
commit 0606046c1a
Notes: git 2025-04-15 00:18:12 +00:00 
Merged: https://github.com/ruby/ruby/pull/13115
5 changed files with 74 additions and 20 deletions
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4
benchmark/object_id.yml Normal file
View File

@ -0,0 +1,4 @@
benchmark:
baseline: "Object.new"
object_id: "Object.new.object_id"
# loop_count: 100000

6
gc.c
View File

@ -1794,11 +1794,11 @@ id2ref(VALUE objid)
return ptr;
}
else {
rb_raise(rb_eRangeError, "%p is not symbol id value", (void *)ptr);
rb_raise(rb_eRangeError, "%p is not a symbol id value", (void *)ptr);
}
}
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is not id value", rb_int2str(objid, 10));
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is not an id value", rb_int2str(objid, 10));
}
}
@ -1807,7 +1807,7 @@ id2ref(VALUE objid)
return obj;
}
else {
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is id of the unshareable object on multi-ractor", rb_int2str(objid, 10));
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is the id of an unshareable object on multi-ractor", rb_int2str(objid, 10));
}
}

45
gc/default/default.c
View File

@ -1585,7 +1585,9 @@ rb_gc_impl_object_id(void *objspace_ptr, VALUE obj)
objspace->next_object_id += OBJ_ID_INCREMENT;
st_insert(objspace->obj_to_id_tbl, (st_data_t)obj, (st_data_t)id);
st_insert(objspace->id_to_obj_tbl, (st_data_t)id, (st_data_t)obj);
if (RB_UNLIKELY(objspace->id_to_obj_tbl)) {
st_insert(objspace->id_to_obj_tbl, (st_data_t)id, (st_data_t)obj);
}
FL_SET(obj, FL_SEEN_OBJ_ID);
}
rb_gc_vm_unlock(lev);
@ -1593,22 +1595,40 @@ rb_gc_impl_object_id(void *objspace_ptr, VALUE obj)
return id;
}
static int
build_id_to_obj_i(st_data_t key, st_data_t value, st_data_t data)
{
st_table *id_to_obj_tbl = (st_table *)data;
st_insert(id_to_obj_tbl, value, key);
return ST_CONTINUE;
}
VALUE
rb_gc_impl_object_id_to_ref(void *objspace_ptr, VALUE object_id)
{
rb_objspace_t *objspace = objspace_ptr;
unsigned int lev = rb_gc_vm_lock();
if (!objspace->id_to_obj_tbl) {
objspace->id_to_obj_tbl = st_init_table_with_size(&object_id_hash_type, st_table_size(objspace->obj_to_id_tbl));
st_foreach(objspace->obj_to_id_tbl, build_id_to_obj_i, (st_data_t)objspace->id_to_obj_tbl);
}
VALUE obj;
if (st_lookup(objspace->id_to_obj_tbl, object_id, &obj) &&
!rb_gc_impl_garbage_object_p(objspace, obj)) {
bool found = st_lookup(objspace->id_to_obj_tbl, object_id, &obj) && !rb_gc_impl_garbage_object_p(objspace, obj);
rb_gc_vm_unlock(lev);
if (found) {
return obj;
}
if (rb_funcall(object_id, rb_intern(">="), 1, ULL2NUM(objspace->next_object_id))) {
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is not id value", rb_funcall(object_id, rb_intern("to_s"), 1, INT2FIX(10)));
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is not an id value", rb_funcall(object_id, rb_intern("to_s"), 1, INT2FIX(10)));
}
else {
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is recycled object", rb_funcall(object_id, rb_intern("to_s"), 1, INT2FIX(10)));
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is a recycled object", rb_funcall(object_id, rb_intern("to_s"), 1, INT2FIX(10)));
}
}
@ -2644,7 +2664,9 @@ obj_free_object_id(rb_objspace_t *objspace, VALUE obj)
if (st_delete(objspace->obj_to_id_tbl, &o, &id)) {
GC_ASSERT(id);
st_delete(objspace->id_to_obj_tbl, &id, NULL);
if (RB_UNLIKELY(objspace->id_to_obj_tbl)) {
st_delete(objspace->id_to_obj_tbl, &id, NULL);
}
}
else {
rb_bug("Object ID seen, but not in mapping table: %s", rb_obj_info(obj));
@ -7168,7 +7190,9 @@ gc_update_references(rb_objspace_t *objspace)
}
}
gc_ref_update_table_values_only(objspace->obj_to_id_tbl);
gc_update_table_refs(objspace->id_to_obj_tbl);
if (RB_UNLIKELY(objspace->id_to_obj_tbl)) {
gc_update_table_refs(objspace->id_to_obj_tbl);
}
gc_update_table_refs(finalizer_table);
rb_gc_update_vm_references((void *)objspace);
@ -9282,7 +9306,10 @@ rb_gc_impl_objspace_free(void *objspace_ptr)
heap->total_slots = 0;
}
st_free_table(objspace->id_to_obj_tbl);
if (objspace->id_to_obj_tbl) {
st_free_table(objspace->id_to_obj_tbl);
}
st_free_table(objspace->obj_to_id_tbl);
free_stack_chunks(&objspace->mark_stack);
@ -9423,7 +9450,7 @@ rb_gc_impl_objspace_init(void *objspace_ptr)
heap_page_alloc_use_mmap = INIT_HEAP_PAGE_ALLOC_USE_MMAP;
#endif
objspace->next_object_id = OBJ_ID_INITIAL;
objspace->id_to_obj_tbl = st_init_table(&object_id_hash_type);
objspace->id_to_obj_tbl = NULL;
objspace->obj_to_id_tbl = st_init_numtable();
#if RGENGC_ESTIMATE_OLDMALLOC
objspace->rgengc.oldmalloc_increase_limit = gc_params.oldmalloc_limit_min;

37
gc/mmtk/mmtk.c
View File

@ -366,7 +366,9 @@ rb_mmtk_update_obj_id_tables(void)
struct objspace *objspace = rb_gc_get_objspace();
st_foreach(objspace->obj_to_id_tbl, rb_mmtk_update_obj_id_tables_obj_to_id_i, 0);
st_foreach(objspace->id_to_obj_tbl, rb_mmtk_update_obj_id_tables_id_to_obj_i, 0);
if (objspace->id_to_obj_tbl) {
st_foreach(objspace->id_to_obj_tbl, rb_mmtk_update_obj_id_tables_id_to_obj_i, 0);
}
}
static int
@ -1091,7 +1093,7 @@ static const struct st_hash_type object_id_hash_type = {
static void
objspace_obj_id_init(struct objspace *objspace)
{
objspace->id_to_obj_tbl = st_init_table(&object_id_hash_type);
objspace->id_to_obj_tbl = NULL;
objspace->obj_to_id_tbl = st_init_numtable();
objspace->next_object_id = OBJ_ID_INITIAL;
}
@ -1119,7 +1121,9 @@ rb_gc_impl_object_id(void *objspace_ptr, VALUE obj)
objspace->next_object_id += OBJ_ID_INCREMENT;
st_insert(objspace->obj_to_id_tbl, (st_data_t)obj, (st_data_t)id);
st_insert(objspace->id_to_obj_tbl, (st_data_t)id, (st_data_t)obj);
if (RB_UNLIKELY(objspace->id_to_obj_tbl)) {
st_insert(objspace->id_to_obj_tbl, (st_data_t)id, (st_data_t)obj);
}
FL_SET(obj, FL_SEEN_OBJ_ID);
}
rb_gc_vm_unlock(lev);
@ -1127,22 +1131,41 @@ rb_gc_impl_object_id(void *objspace_ptr, VALUE obj)
return id;
}
static int
build_id_to_obj_i(st_data_t key, st_data_t value, st_data_t data)
{
st_table *id_to_obj_tbl = (st_table *)data;
st_insert(id_to_obj_tbl, value, key);
return ST_CONTINUE;
}
VALUE
rb_gc_impl_object_id_to_ref(void *objspace_ptr, VALUE object_id)
{
struct objspace *objspace = objspace_ptr;
unsigned int lev = rb_gc_vm_lock();
if (!objspace->id_to_obj_tbl) {
objspace->id_to_obj_tbl = st_init_table_with_size(&object_id_hash_type, st_table_size(objspace->obj_to_id_tbl));
st_foreach(objspace->obj_to_id_tbl, build_id_to_obj_i, (st_data_t)objspace->id_to_obj_tbl);
}
VALUE obj;
if (st_lookup(objspace->id_to_obj_tbl, object_id, &obj) &&
!rb_gc_impl_garbage_object_p(objspace, obj)) {
bool found = st_lookup(objspace->id_to_obj_tbl, object_id, &obj) && !rb_gc_impl_garbage_object_p(objspace, obj);
rb_gc_vm_unlock(lev);
if (found) {
return obj;
}
if (rb_funcall(object_id, rb_intern(">="), 1, ULL2NUM(objspace->next_object_id))) {
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is not id value", rb_funcall(object_id, rb_intern("to_s"), 1, INT2FIX(10)));
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is not an id value", rb_funcall(object_id, rb_intern("to_s"), 1, INT2FIX(10)));
}
else {
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is recycled object", rb_funcall(object_id, rb_intern("to_s"), 1, INT2FIX(10)));
rb_raise(rb_eRangeError, "%+"PRIsVALUE" is a recycled object", rb_funcall(object_id, rb_intern("to_s"), 1, INT2FIX(10)));
}
}

2
test/ruby/test_objectspace.rb
View File

@ -69,7 +69,7 @@ End
# RB_STATIC_SYM_P checks for static symbols by checking that the bottom
# 8 bits of the object is equal to RUBY_SYMBOL_FLAG, so we need to make
# sure that the bottom 8 bits remain unchanged.
msg = /is not symbol id value/
msg = /is not a symbol id value/
assert_raise_with_message(RangeError, msg) { ObjectSpace._id2ref(:a.object_id + 256) }
end