ObjectSpace.dump_all: dump shapes as well

I see several arguments in doing so.

First they use a non trivial amount of memory, so for various memory
profiling/mapping tools it is relevant to have visibility of the space
occupied by shapes.

Then, some pathological code can create a tons of shape, so it is
valuable to have a way to have a way to observe shapes without having
to compile Ruby with `SHAPE_DEBUG=1`.

And additionally it's likely much faster to dump then this way than
to use `RubyVM::Shape`.

There are however a few open questions:

- Shapes can't respect the `since:` argument. Not sure what to do when
  it is provided. Would probably make sense to not dump them.
- Maybe it would make more sense to have a separate `ObjectSpace.dump_shapes`?
- Maybe instead `dump_all` should take a `shapes: false` argument?

Additionally, `ObjectSpace.dump_shapes` is added for the use case of
debugging the evolution of the shape tree.

1 files changed, 110 insertions, 8 deletions

diff --git a/ext/objspace/objspace_dump.c b/ext/objspace/objspace_dump.c
index 41da368267..bcc258eb25 100644
--- a/ext/objspace/objspace_dump.c
+++ b/ext/objspace/objspace_dump.c
@@ -18,6 +18,8 @@
 #include "internal/hash.h"
 #include "internal/string.h"
 #include "internal/sanitizers.h"
+#include "symbol.h"
+#include "shape.h"
 #include "node.h"
 #include "objspace.h"
 #include "ruby/debug.h"
@@ -42,6 +44,7 @@ struct dump_config {
     unsigned int full_heap: 1;
     unsigned int partial_dump;
     size_t since;
+    size_t shapes_since;
     unsigned long buffer_len;
     char buffer[BUFFER_CAPACITY];
 };
@@ -350,6 +353,20 @@ dump_append_string_content(struct dump_config *dc, VALUE obj)
     }
 }
 
+static inline void
+dump_append_id(struct dump_config *dc, ID id)
+{
+    if (is_instance_id(id)) {
+        dump_append_string_value(dc, rb_sym2str(ID2SYM(id)));
+    }
+    else {
+        dump_append(dc, "\"ID_INTERNAL(");
+        dump_append_sizet(dc, rb_id_to_serial(id));
+        dump_append(dc, ")\"");
+    }
+}
+
+
 static void
 dump_object(VALUE obj, struct dump_config *dc)
 {
@@ -378,13 +395,16 @@ dump_object(VALUE obj, struct dump_config *dc)
     dump_append(dc, "{\"address\":");
     dump_append_ref(dc, obj);
 
-    dump_append(dc, ", \"shape_id\":");
-    dump_append_sizet(dc, rb_shape_get_shape_id(obj));
-
     dump_append(dc, ", \"type\":\"");
     dump_append(dc, obj_type(obj));
     dump_append(dc, "\"");
 
+    size_t shape_id = rb_shape_get_shape_id(obj);
+    if (shape_id) {
+        dump_append(dc, ", \"shape_id\":");
+        dump_append_sizet(dc, shape_id);
+    }
+
     dump_append(dc, ", \"slot_size\":");
     dump_append_sizet(dc, dc->cur_page_slot_size);
 
@@ -622,7 +642,7 @@ root_obj_i(const char *category, VALUE obj, void *data)
 }
 
 static void
-dump_output(struct dump_config *dc, VALUE output, VALUE full, VALUE since)
+dump_output(struct dump_config *dc, VALUE output, VALUE full, VALUE since, VALUE shapes)
 {
 
     dc->full_heap = 0;
@@ -648,6 +668,8 @@ dump_output(struct dump_config *dc, VALUE output, VALUE full, VALUE since)
     else {
         dc->partial_dump = 0;
     }
+
+    dc->shapes_since = RTEST(shapes) ? NUM2SIZET(shapes) : 0;
 }
 
 static VALUE
@@ -672,18 +694,81 @@ objspace_dump(VALUE os, VALUE obj, VALUE output)
         dc.cur_page_slot_size = rb_gc_obj_slot_size(obj);
     }
 
-    dump_output(&dc, output, Qnil, Qnil);
+    dump_output(&dc, output, Qnil, Qnil, Qnil);
 
     dump_object(obj, &dc);
 
     return dump_result(&dc);
 }
 
+static void
+shape_i(rb_shape_t *shape, void *data)
+{
+    struct dump_config *dc = (struct dump_config *)data;
+
+    size_t shape_id = rb_shape_id(shape);
+    if (shape_id < dc->shapes_since) {
+        return;
+    }
+
+    dump_append(dc, "{\"address\":");
+    dump_append_ref(dc, (VALUE)shape);
+
+    dump_append(dc, ", \"type\":\"SHAPE\", \"id\":");
+    dump_append_sizet(dc, shape_id);
+
+    if (shape->type != SHAPE_ROOT) {
+        dump_append(dc, ", \"parent_id\":");
+        dump_append_lu(dc, shape->parent_id);
+    }
+
+    dump_append(dc, ", \"depth\":");
+    dump_append_sizet(dc, rb_shape_depth(shape));
+
+    dump_append(dc, ", \"shape_type\":");
+    switch(shape->type) {
+      case SHAPE_ROOT:
+        dump_append(dc, "\"ROOT\"");
+        break;
+      case SHAPE_IVAR:
+        dump_append(dc, "\"IVAR\"");
+
+        dump_append(dc, ",\"edge_name\":");
+        dump_append_id(dc, shape->edge_name);
+
+        break;
+      case SHAPE_FROZEN:
+        dump_append(dc, "\"FROZEN\"");
+        break;
+      case SHAPE_CAPACITY_CHANGE:
+        dump_append(dc, "\"CAPACITY_CHANGE\"");
+        dump_append(dc, ", \"capacity\":");
+        dump_append_sizet(dc, shape->capacity);
+        break;
+      case SHAPE_INITIAL_CAPACITY:
+        dump_append(dc, "\"INITIAL_CAPACITY\"");
+        break;
+      case SHAPE_T_OBJECT:
+        dump_append(dc, "\"T_OBJECT\"");
+        break;
+      default:
+        rb_bug("[objspace] unexpected shape type");
+    }
+
+    dump_append(dc, ", \"edges\":");
+    dump_append_sizet(dc, rb_shape_edges_count(shape));
+
+    dump_append(dc, ", \"memsize\":");
+    dump_append_sizet(dc, rb_shape_memsize(shape));
+
+    dump_append(dc, "}\n");
+}
+
 static VALUE
-objspace_dump_all(VALUE os, VALUE output, VALUE full, VALUE since)
+objspace_dump_all(VALUE os, VALUE output, VALUE full, VALUE since, VALUE shapes)
 {
     struct dump_config dc = {0,};
-    dump_output(&dc, output, full, since);
+    dump_output(&dc, output, full, since, shapes);
 
     if (!dc.partial_dump || dc.since == 0) {
         /* dump roots */
@@ -691,12 +776,28 @@ objspace_dump_all(VALUE os, VALUE output, VALUE full, VALUE since)
         if (dc.roots) dump_append(&dc, "]}\n");
     }
 
+    if (RTEST(shapes)) {
+        rb_shape_each_shape(shape_i, &dc);
+    }
+
     /* dump all objects */
     rb_objspace_each_objects(heap_i, &dc);
 
     return dump_result(&dc);
 }
 
+static VALUE
+objspace_dump_shapes(VALUE os, VALUE output, VALUE shapes)
+{
+    struct dump_config dc = {0,};
+    dump_output(&dc, output, Qfalse, Qnil, shapes);
+
+    if (RTEST(shapes)) {
+        rb_shape_each_shape(shape_i, &dc);
+    }
+    return dump_result(&dc);
+}
+
 void
 Init_objspace_dump(VALUE rb_mObjSpace)
 {
@@ -706,7 +807,8 @@ Init_objspace_dump(VALUE rb_mObjSpace)
 #endif
 
     rb_define_module_function(rb_mObjSpace, "_dump", objspace_dump, 2);
-    rb_define_module_function(rb_mObjSpace, "_dump_all", objspace_dump_all, 3);
+    rb_define_module_function(rb_mObjSpace, "_dump_all", objspace_dump_all, 4);
+    rb_define_module_function(rb_mObjSpace, "_dump_shapes", objspace_dump_shapes, 2);
 
     /* force create static IDs */
     rb_obj_gc_flags(rb_mObjSpace, 0, 0);