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Speed up shape transitions

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This commit significantly speeds up shape transitions as it changes
get_next_shape_internal to not perform a lookup (and instead require
the caller to perform the lookup). This avoids double lookups during
shape transitions.

There is a significant (~2x) speedup in the following micro-benchmark:

    puts(Benchmark.measure do
      o = Object.new

      100_000.times do |i|
        o.instance_variable_set(:"@a#{i}", 0)
      end
    end)

Before:

    22.393194   0.201639  22.594833 ( 22.684237)

After:

    11.323086   0.022284  11.345370 ( 11.389346)
This commit is contained in:
Peter Zhu 2022-11-17 09:47:18 -05:00
parent 648927d71b
commit 1f0888ab3e
Notes: git 2022-11-21 15:22:54 +00:00 
Merged: https://github.com/ruby/ruby/pull/6751
2 changed files with 46 additions and 70 deletions
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91
shape.c
View File

@ -98,74 +98,49 @@ rb_shape_get_shape(VALUE obj)
return rb_shape_get_shape_by_id(rb_shape_get_shape_id(obj));
}
static rb_shape_t *
rb_shape_lookup_id(rb_shape_t* shape, ID id, enum shape_type shape_type)
{
while (shape->parent_id != INVALID_SHAPE_ID) {
if (shape->edge_name == id) {
// If the shape type is different, we don't
// want this to count as a "found" ID
if (shape_type == (enum shape_type)shape->type) {
return shape;
}
else {
return NULL;
}
}
shape = rb_shape_get_parent(shape);
}
return NULL;
}
static rb_shape_t*
get_next_shape_internal(rb_shape_t * shape, ID id, enum shape_type shape_type)
{
rb_shape_t *res = NULL;
RB_VM_LOCK_ENTER();
{
if (rb_shape_lookup_id(shape, id, shape_type)) {
// If shape already contains the ivar that is being set, we'll return shape
res = shape;
if (!shape->edges) {
shape->edges = rb_id_table_create(0);
}
else {
if (!shape->edges) {
shape->edges = rb_id_table_create(0);
// Lookup the shape in edges - if there's already an edge and a corresponding shape for it,
// we can return that. Otherwise, we'll need to get a new shape
if (!rb_id_table_lookup(shape->edges, id, (VALUE *)&res)) {
// In this case, the shape exists, but the shape is garbage, so we need to recreate it
if (res) {
rb_id_table_delete(shape->edges, id);
res->parent_id = INVALID_SHAPE_ID;
}
// Lookup the shape in edges - if there's already an edge and a corresponding shape for it,
// we can return that. Otherwise, we'll need to get a new shape
if (!rb_id_table_lookup(shape->edges, id, (VALUE *)&res)) {
// In this case, the shape exists, but the shape is garbage, so we need to recreate it
if (res) {
rb_id_table_delete(shape->edges, id);
res->parent_id = INVALID_SHAPE_ID;
}
rb_shape_t * new_shape = rb_shape_alloc(id, shape);
rb_shape_t * new_shape = rb_shape_alloc(id, shape);
new_shape->type = (uint8_t)shape_type;
new_shape->capacity = shape->capacity;
new_shape->type = (uint8_t)shape_type;
new_shape->capacity = shape->capacity;
switch (shape_type) {
case SHAPE_IVAR:
new_shape->next_iv_index = shape->next_iv_index + 1;
break;
case SHAPE_CAPACITY_CHANGE:
case SHAPE_IVAR_UNDEF:
case SHAPE_FROZEN:
case SHAPE_T_OBJECT:
new_shape->next_iv_index = shape->next_iv_index;
break;
case SHAPE_INITIAL_CAPACITY:
case SHAPE_ROOT:
rb_bug("Unreachable");
break;
}
rb_id_table_insert(shape->edges, id, (VALUE)new_shape);
res = new_shape;
switch (shape_type) {
case SHAPE_IVAR:
new_shape->next_iv_index = shape->next_iv_index + 1;
break;
case SHAPE_CAPACITY_CHANGE:
case SHAPE_IVAR_UNDEF:
case SHAPE_FROZEN:
case SHAPE_T_OBJECT:
new_shape->next_iv_index = shape->next_iv_index;
break;
case SHAPE_INITIAL_CAPACITY:
case SHAPE_ROOT:
rb_bug("Unreachable");
break;
}
rb_id_table_insert(shape->edges, id, (VALUE)new_shape);
res = new_shape;
}
}
RB_VM_LOCK_LEAVE();
@ -183,10 +158,6 @@ rb_shape_transition_shape_remove_ivar(VALUE obj, ID id, rb_shape_t *shape)
{
rb_shape_t * next_shape = get_next_shape_internal(shape, id, SHAPE_IVAR_UNDEF);
if (shape == next_shape) {
return;
}
rb_shape_set_shape(obj, next_shape);
}

25
variable.c
View File

@ -1276,28 +1276,33 @@ static void
generic_ivar_set(VALUE obj, ID id, VALUE val)
{
struct ivar_update ivup;
attr_index_t index;
// The returned shape will have `id` in its iv_table
rb_shape_t * shape = rb_shape_get_next(rb_shape_get_shape(obj), obj, id);
rb_shape_t *shape = rb_shape_get_shape(obj);
bool found = rb_shape_get_iv_index(shape, id, &index);
if (!found) {
index = shape->next_iv_index;
shape = rb_shape_get_next(shape, obj, id);
RUBY_ASSERT(index == (shape->next_iv_index - 1));
}
ivup.shape = shape;
RB_VM_LOCK_ENTER();
{
attr_index_t ent_data;
if (rb_shape_get_iv_index(shape, id, &ent_data)) {
ivup.iv_index = (uint32_t) ent_data;
}
else {
rb_bug("unreachable. Shape was not found for id: %s", rb_id2name(id));
}
ivup.iv_index = (uint32_t)index;
st_update(generic_ivtbl(obj, id, false), (st_data_t)obj, generic_ivar_update, (st_data_t)&ivup);
}
RB_VM_LOCK_LEAVE();
ivup.ivtbl->ivptr[ivup.iv_index] = val;
rb_shape_set_shape(obj, shape);
RB_OBJ_WRITTEN(obj, Qundef, val);
if (!found) {
rb_shape_set_shape(obj, shape);
}
}
static VALUE *