[ruby-core:38220] Re: [Ruby 1.9 - Feature #5033][Open] PATCH: 1.9: gc_mark_children: Avoid gc_mark() tail recursion, use goto again.

Eric Wong <[e-mail]> wrote:
> Kurt Stephens <[e-mail]> wrote:
> > Feature #5033: PATCH: 1.9: gc_mark_children: Avoid gc_mark() tail recursion, use goto again.
> > http://redmine.ruby-lang.org/issues/5033
> 
> In [ruby-core:36931], ko1 told us GC eats stack when marking nested
> objects.  Kurt's patch should allow us to run smaller pthread stack
> sizes while still supporting deeply-nested structures.

shyouhei appears right about compilers being able to optimize this
for the easy cases.

However "inspect" on deeply-nested structures is still stack hungry and
causes SystemStackErrors on my machine if I try to "p" a deeply-nested
array or hash.

> Kurt: can you test a smaller stack size with your patch with some
> deeply-nested objects?

I was playing around with something like this (but did not
get any useful results/conclusion either way):

def deeper!(array_or_hash, depth)
  if depth > 6000
    $last = array_or_hash[0] = {}
  else
    array_or_hash[0] = [ deeper!({}, depth += 1) ]
  end
end

orig = {}
deeper!(orig, 0)
5000.times do |i|
  deeper!($last, 0)
end
p $$
# give GC something to much on
100000.times { |i| i.to_s }
p :done