[ruby-core:57651] [ruby-trunk - Bug #8983] [PATCH] GC.stat[:heap_free_num] returns number of unused slots on heap

Issue #8983 has been updated by tmm1 (Aman Gupta).


I understand the slot is removed, but `objspace_live_num` includes unfinalized objects so I included them in `heap_limit` also.

Otherwise, `objspace->heap.limit - objspace_live_num(objspace)` can become negative.
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Bug #8983: [PATCH] GC.stat[:heap_free_num] returns number of unused slots on heap
https://bugs.ruby-lang.org/issues/8983#change-42269

Author: tmm1 (Aman Gupta)
Status: Assigned
Priority: Normal
Assignee: ko1 (Koichi Sasada)
Category: 
Target version: current: 2.1.0
ruby -v: ruby 2.1.0dev (2013-10-03 trunk 43129) [x86_64-darwin12.4.1]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


In ruby 1.9 and 2.0, gc_stat() used to call rest_sweep() so heap_free_num always equals the number of free slots (ObjectSpace.count_objects[:FREE]). In 2.1 the rest_sweep() was removed, so free_num is not always accurate. This patch fixes compatibility with the previous behavior.

With this patch, it is also easier to perform "out-of-band" GC in unicorn and passenger. For example: if your application requires 100k objects per request, then you can run the following in-between every request:

  GC.start if GC.stat[:heap_free_num] < 100_000

I also added a objspace->heap.limit because HEAP_OBJ_LIMIT*heap_used is not accurate due to memory re-alignment in heap_assign_slot.

https://github.com/tmm1/ruby/compare/gc-stat-free-num
https://github.com/tmm1/ruby/compare/gc-stat-free-num.patch


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