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authorAlan Wu <XrXr@users.noreply.github.com>2020-11-12 15:15:30 -0500
committerAlan Wu <XrXr@users.noreply.github.com>2020-11-16 17:41:40 -0500
commit68ffc8db088a7b29613a3746be5cc996be9f66fe (patch)
tree42e85d9981cdbfb0fed7bc4d1582ae4861383dfc
parentebb96fa8808317ad53a4977bff26cf755d68077e (diff)
Set allocator on class creation
Allocating an instance of a class uses the allocator for the class. When the class has no allocator set, Ruby looks for it in the super class (see rb_get_alloc_func()). It's uncommon for classes created from Ruby code to ever have an allocator set, so it's common during the allocation process to search all the way to BasicObject from the class with which the allocation is being performed. This makes creating instances of classes that have long ancestry chains more expensive than creating instances of classes have that shorter ancestry chains. Setting the allocator at class creation time removes the need to perform a search for the alloctor during allocation. This is a breaking change for C-extensions that assume that classes created from Ruby code have no allocator set. Libraries that setup a class hierarchy in Ruby code and then set the allocator on some parent class, for example, can experience breakage. This seems like an unusual use case and hopefully it is rare or non-existent in practice. Rails has many classes that have upwards of 60 elements in the ancestry chain and benchmark shows a significant improvement for allocating with a class that includes 64 modules. ``` pre: ruby 3.0.0dev (2020-11-12T14:39:27Z master 6325866421) post: ruby 3.0.0dev (2020-11-12T20:15:30Z cut-allocator-lookup) Comparison: allocate_8_deep post: 10336985.6 i/s pre: 8691873.1 i/s - 1.19x slower allocate_32_deep post: 10423181.2 i/s pre: 6264879.1 i/s - 1.66x slower allocate_64_deep post: 10541851.2 i/s pre: 4936321.5 i/s - 2.14x slower allocate_128_deep post: 10451505.0 i/s pre: 3031313.5 i/s - 3.45x slower ```
Notes
Notes: Merged: https://github.com/ruby/ruby/pull/3764
-rw-r--r--benchmark/object_allocate.yml21
-rw-r--r--vm_insnhelper.c1
2 files changed, 22 insertions, 0 deletions
diff --git a/benchmark/object_allocate.yml b/benchmark/object_allocate.yml
new file mode 100644
index 0000000000..93ff463e41
--- /dev/null
+++ b/benchmark/object_allocate.yml
@@ -0,0 +1,21 @@
+prelude: |
+ class Eight
+ 8.times { include(Module.new) }
+ end
+ class ThirtyTwo
+ 32.times { include(Module.new) }
+ end
+ class SixtyFour
+ 64.times { include(Module.new) }
+ end
+ class OneTwentyEight
+ 128.times { include(Module.new) }
+ end
+ # Disable GC to see raw throughput:
+ GC.disable
+benchmark:
+ allocate_8_deep: Eight.new
+ allocate_32_deep: ThirtyTwo.new
+ allocate_64_deep: SixtyFour.new
+ allocate_128_deep: OneTwentyEight.new
+loop_count: 100000
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 2fa96373b6..f902a65f34 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -4034,6 +4034,7 @@ vm_declare_class(ID id, rb_num_t flags, VALUE cbase, VALUE super)
/* new class declaration */
VALUE s = VM_DEFINECLASS_HAS_SUPERCLASS_P(flags) ? super : rb_cObject;
VALUE c = declare_under(id, cbase, rb_define_class_id(id, s));
+ rb_define_alloc_func(c, rb_get_alloc_func(c));
rb_class_inherited(s, c);
return c;
}