Bug #9225: [patch] add WB to NODE_CREF

• Status: Closed
• Assignee: ko1 (Koichi Sasada)
• Target version: 2.1.0
• ruby -v: trunk
• Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN

[tmm1 (Aman Karmani)]

In our rails app, there are a lot of long-lived NODE_CREF:

p ObjectSpace.count_nodes
=> {:NODE_IF=>3, :NODE_CREF=>45810, :NODE_IFUNC=>11}

These are static objects, but are considered SHADY and contribute to the size of the remembered set:

GC.stat[:remembered_shady_object]
=> 49667

With the following patch, NODE_CREF are no longer shady and can be promoted: https://github.com/tmm1/ruby/commit/c5e8341

This reduces the size of the remembered set in our app, and speeds up minor GC from 22ms to 18ms per run.
After the patch:

GC.stat[:remembered_shady_object]
=> 10506

The patch is passing make test-all with RGENGC_CHECK=2

[tmm1 (Aman Karmani)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

This issue was solved with changeset r44059.
Aman, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

---

gc.c: promote long-lived NODE_CREF objects to oldgen

• include/ruby/ruby.h: add RGENGC_WB_PROTECTED_NODE_CREF setting
  In a large app, this reduces the size of
  remembered_shady_object_count by 80%. [Bug #9225] [ruby-core:58947]
• gc.c (rb_node_newnode): add FL_WB_PROTECTED flag to NODE_CREF
• class.c (rewrite_cref_stack): insert OBJ_WRITE for NODE_CREF
• iseq.c (set_relation): ditto
• iseq.c (rb_iseq_clone): ditto
• vm_eval.c (rb_yield_refine_block): ditto
• vm_insnhelper.c (vm_cref_push): ditto
• vm_insnhelper.h (COPY_CREF): ditto