imemo_fields_set: save copying when reassigning a variable

If we still fit in the existing imemo/fields object we can
update it atomically, saving a reallocation.
This commit is contained in:
Jean Boussier 2025-07-02 13:10:24 +02:00
parent a020e3490a
commit 517c106709
3 changed files with 41 additions and 8 deletions

View file

@ -566,9 +566,7 @@ RCLASSEXT_SET_FIELDS_OBJ(VALUE obj, rb_classext_t *ext, VALUE fields_obj)
{
RUBY_ASSERT(RB_TYPE_P(obj, RUBY_T_CLASS) || RB_TYPE_P(obj, RUBY_T_MODULE));
VALUE old_fields_obj = ext->fields_obj;
RUBY_ATOMIC_VALUE_SET(ext->fields_obj, fields_obj);
RB_OBJ_WRITTEN(obj, old_fields_obj, fields_obj);
RB_OBJ_ATOMIC_WRITE(obj, &ext->fields_obj, fields_obj);
}
static inline void

View file

@ -264,6 +264,26 @@ int rb_gc_modular_gc_loaded_p(void);
RUBY_SYMBOL_EXPORT_END
static inline VALUE
rb_obj_atomic_write(
VALUE a, VALUE *slot, VALUE b,
RBIMPL_ATTR_MAYBE_UNUSED()
const char *filename,
RBIMPL_ATTR_MAYBE_UNUSED()
int line)
{
#ifdef RGENGC_LOGGING_WRITE
RGENGC_LOGGING_WRITE(a, slot, b, filename, line);
#endif
RUBY_ATOMIC_VALUE_SET(*slot, b);
rb_obj_written(a, RUBY_Qundef /* ignore `oldv' now */, b, filename, line);
return a;
}
#define RB_OBJ_ATOMIC_WRITE(old, slot, young) \
RBIMPL_CAST(rb_obj_atomic_write((VALUE)(old), (VALUE *)(slot), (VALUE)(young), __FILE__, __LINE__))
int rb_ec_stack_check(struct rb_execution_context_struct *ec);
void rb_gc_writebarrier_remember(VALUE obj);
const char *rb_obj_info(VALUE obj);

View file

@ -1844,6 +1844,9 @@ imemo_fields_set(VALUE klass, VALUE fields_obj, shape_id_t target_shape_id, ID f
if (UNLIKELY(rb_shape_too_complex_p(target_shape_id))) {
if (rb_shape_too_complex_p(current_shape_id)) {
if (concurrent) {
// In multi-ractor case, we must always work on a copy because
// even if the field already exist, inserting in a st_table may
// cause a rebuild.
fields_obj = rb_imemo_fields_clone(fields_obj);
}
}
@ -4680,9 +4683,7 @@ class_fields_ivar_set(VALUE klass, VALUE fields_obj, ID id, VALUE val, bool conc
attr_index_t next_capacity = RSHAPE_CAPACITY(next_shape_id);
attr_index_t current_capacity = RSHAPE_CAPACITY(current_shape_id);
if (concurrent || next_capacity != current_capacity) {
RUBY_ASSERT(concurrent || next_capacity > current_capacity);
if (next_capacity > current_capacity) {
// We allocate a new fields_obj even when concurrency isn't a concern
// so that we're embedded as long as possible.
fields_obj = imemo_fields_copy_capa(rb_singleton_class(klass), fields_obj, next_capacity);
@ -4693,7 +4694,18 @@ class_fields_ivar_set(VALUE klass, VALUE fields_obj, ID id, VALUE val, bool conc
}
VALUE *fields = rb_imemo_fields_ptr(fields_obj);
RB_OBJ_WRITE(fields_obj, &fields[index], val);
if (concurrent && original_fields_obj == fields_obj) {
// In the concurrent case, if we're mutating the existing
// fields_obj, we must use an atomic write, because if we're
// adding a new field, the shape_id must be written after the field
// and if we're updating an existing field, we at least need a relaxed
// write to avoid reaping.
RB_OBJ_ATOMIC_WRITE(fields_obj, &fields[index], val);
}
else {
RB_OBJ_WRITE(fields_obj, &fields[index], val);
}
if (!existing) {
RBASIC_SET_SHAPE_ID(fields_obj, next_shape_id);
@ -4705,9 +4717,12 @@ class_fields_ivar_set(VALUE klass, VALUE fields_obj, ID id, VALUE val, bool conc
too_complex:
{
if (concurrent && fields_obj == original_fields_obj) {
// If we're in the multi-ractor mode, we can't directly insert in the table.
// In multi-ractor case, we must always work on a copy because
// even if the field already exist, inserting in a st_table may
// cause a rebuild.
fields_obj = rb_imemo_fields_clone(fields_obj);
}
st_table *table = rb_imemo_fields_complex_tbl(fields_obj);
existing = st_insert(table, (st_data_t)id, (st_data_t)val);
RB_OBJ_WRITTEN(fields_obj, Qundef, val);