Make compaction available for Oj::Doc (#653)

* Make compaction available for `Oj::Doc`

Introduce compaction to `fast.c`, only if `rb_gc_mark_movable` is
available. Otherwise, keep a version that supports ruby <2.7.

Since `rb_data_object_wrap` and `TypedData_Wrap_Struct` is available
in every supported versions (eg >=2.4.10), I've also removed support
for earlier versions.

Result for compaction is great. I've tested it by allocating and
removing arbitrary sized json. For a count of 70 pages, we can see
that we used to need 68 pages after compaction,and now 61 pages. Of
course this test include also lots of noise, but if we count pinned
objects (objects that are marked in C extension as uncollectible),
we can see that for a benchmark with no allocations, we have the
same amount as a benchmark with this commit with thousands of allocations
(499 pinned objects total), and before this, `Oj::Doc` used to generate
5k more objects (5499 pinned objects total).

Hence this is a win, see #650 for a graphical result.

Signed-off-by: Ulysse Buonomo <buonomo.ulysse@gmail.com>

* Change `clang-format` -> `.clang-format`

According to clang's documentation:

> When using `-style=file`, **clang-format** for each input file will
> try to find the `.clang-format` file located in the closest parent
> directory of the input file. When the standard input is used, the
> search is started from the current directory.

Hence the `.clang-format` seems more appropriate

Signed-off-by: Ulysse Buonomo <buonomo.ulysse@gmail.com>

CHANGELOG.md

@@ -5,7 +5,7 @@
 - Code re-formatted with clang-format. Thanks goes to BuonOmo for
   suggesting and encouraging the use of a formatter and getting the
   effort started.
-
+- Added support for `GC.compact` on `Oj::Doc`
 
 ## 3.11.3 - 2021-03-09
 

Rakefile

@@ -92,4 +92,3 @@ begin
 
 rescue LoadError
 end
-

ext/oj/extconf.rb

@@ -26,8 +26,9 @@
 have_func('rb_time_timespec')
 have_func('rb_ivar_count')
 have_func('rb_ivar_foreach')
+# Support for compaction.
+have_func('rb_gc_mark_movable')
 have_func('stpcpy')
-have_func('rb_data_object_wrap')
 have_func('pthread_mutex_init')
 
 dflags['OJ_DEBUG'] = true unless ENV['OJ_DEBUG'].nil?

ext/oj/fast.c

@@ -20,6 +20,13 @@
 //#define BATCH_SIZE	(4096 / sizeof(struct _leaf) - 1)
 #define BATCH_SIZE 100
 
+// Support for compaction
+#ifdef HAVE_RB_GC_MARK_MOVABLE
+#define mark rb_gc_mark_movable
+#else
+#define mark rb_gc_mark
+#endif
+
 typedef struct _batch {
     struct _batch *next;
     int            next_avail;
@@ -699,7 +706,7 @@ static void mark_leaf(Leaf leaf) {
             } while (e != first);
         }
         break;
-    case RUBY_VAL: rb_gc_mark(leaf->value); break;
+    case RUBY_VAL: mark(leaf->value); break;
 
     default: break;
     }
@@ -709,10 +716,53 @@ static void mark_doc(void *ptr) {
     if (NULL != ptr) {
         Doc doc = (Doc)ptr;
 
-        rb_gc_mark(doc->self);
+        mark(doc->self);
         mark_leaf(doc->data);
     }
 }
+#ifdef HAVE_RB_GC_MARK_MOVABLE
+static void compact_leaf(Leaf leaf) {
+    switch (leaf->value_type) {
+    case COL_VAL:
+        if (NULL != leaf->elements) {
+            Leaf first = leaf->elements->next;
+            Leaf e     = first;
+
+            do {
+                compact_leaf(e);
+                e = e->next;
+            } while (e != first);
+        }
+        break;
+    case RUBY_VAL: leaf->value = rb_gc_location(leaf->value); break;
+
+    default: break;
+    }
+}
+
+static void compact_doc(void *ptr) {
+    Doc doc = (Doc)ptr;
+
+    if (doc) {
+        doc->self = rb_gc_location(doc->self);
+        compact_leaf(doc->data);
+    }
+}
+#endif
+
+static const rb_data_type_t oj_doc_type = {
+    "Oj/doc",
+    {
+        mark_doc,
+        free_doc_cb,
+        NULL,
+#ifdef HAVE_RB_GC_MARK_MOVABLE
+        compact_doc,
+#endif
+    },
+    0,
+    0,
+};
 
 static VALUE parse_json(VALUE clas, char *json, bool given, bool allocated) {
     struct _parseInfo pi;
@@ -752,12 +802,7 @@ static VALUE parse_json(VALUE clas, char *json, bool given, bool allocated) {
         }
     }
 #endif
-    // last arg is free func void* func(void*)
-#ifdef HAVE_RB_DATA_OBJECT_WRAP
-    self = rb_data_object_wrap(clas, doc, mark_doc, free_doc_cb);
-#else
-    self = rb_data_object_alloc(clas, doc, mark_doc, free_doc_cb);
-#endif
+    self                = TypedData_Wrap_Struct(clas, &oj_doc_type, doc);
     doc->self           = self;
     doc->json           = json;
     DATA_PTR(doc->self) = doc;

lib/oj/bag.rb

@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 
 module Oj
 

test/test_scp.rb

@@ -328,7 +328,7 @@ def test_pipe
     IO.pipe do |read_io, write_io|
       if fork
         write_io.close
-        Oj.sc_parse(handler, read_io) {|v| p v}
+        Oj.sc_parse(handler, read_io)
         read_io.close
         assert_equal([[:hash_start],
                       [:hash_key, 'one'],