From: Eric Hodel <drbrain@...7.net>
Date: 2011-07-07T07:26:18+09:00
Subject: [ruby-core:37835] Re: [Ruby 1.9 - Bug #4962] come back gem_prelude!

On Jul 6, 2011, at 3:02 PM, Benoit Daloze wrote:

> On 6 July 2011 23:21, Eric Hodel <drbrain@segment7.net> wrote:
>> 
>> Please try r32429
> 
> I just tried, and here are some numbers.
> Surprising how such a change can move numbers.
> 
> $ time ruby -e ''
> before: 0.045
> no-gems: 0.013
> after: 0.024
> 
> $ ruby -e 'p ObjectSpace.count_objects[:TOTAL]'
> before: 20033
> no-gems: 9811
> after: 14308

I'm unsure if TOTAL is counting what we think it's counting.  It seems to be showing the size of the object space not the number of allocated objects.  If you add allocated and FREE from the output below you'll get TOTAL.

$ cat diffhash.rb 
gems    = eval `#{Gem.ruby} -e 'GC.start; p ObjectSpace.count_objects' | grep '{'`
no_gems = eval `#{Gem.ruby} --disable-gems -e 'GC.start; p ObjectSpace.count_objects' | grep '{'`

gems[:allocated]    =
  gems.select { |k,_| k.to_s.start_with? 'T_' }.values.inject :+

no_gems[:allocated] =
  no_gems.select { |k,_| k.to_s.start_with? 'T_' }.values.inject :+

puts "               gems  no_gems     diff"

gems.keys.sort.each do |key|
  a = gems[key].to_i
  b = no_gems[key].to_i

  puts "%-10s %8d %8d %8d" % [key, a, b, a - b]
end

$ ./ruby19 diffhash.rb 
               gems  no_gems     diff
FREE           6793     7357     -564
TOTAL         14309     9811     4498
T_ARRAY         226       20      206
T_BIGNUM          3        3        0
T_CLASS         474      425       49
T_COMPLEX         1        1        0
T_DATA          347      117      230
T_FILE            3        3        0
T_FLOAT           7        7        0
T_HASH            7        3        4
T_ICLASS         19       18        1
T_MODULE         21       18        3
T_NODE         3185       27     3158
T_OBJECT          7        6        1
T_REGEXP         24        8       16
T_STRING       3192     1798     1394
allocated      7516     2454     5062

Also, the GC runs once at ruby startup:

$ ruby19 --disable-gems -e 'GC::Profiler.enable; require "rubygems"; puts GC::Profiler.result'
GC 1 invokes.
Index    Invoke Time(sec)       Use Size(byte)     Total Size(byte)         Total Object                    GC Time(ms)
    1               0.009               288200               409000                10225         0.41599999999999970335

Increasing HEAP_MIN_SLOTS to 20000 eliminates the initial garbage collection:

$ RUBY_HEAP_MIN_SLOTS=20000 ruby19 --disable-gems -e 'GC::Profiler.enable; require "rubygems"; puts GC::Profiler.result'
heap_min_slots=20000 (10000)